Saudi Aramco Engineering Standards-Electrical-Commissioning

Engineering Encyclopedia Saudi Aramco DeskTop Standards

Directing The Startup And Commissioning Of Motors

Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.

Chapter : Electrical File Reference: EEX20304

For additional information on this subject, contact W.A. Roussel on 874-1320

Engineering Encyclopedia

Electrical Directing the Startup and Commissioning of Motors

CONTENTS

PAGE

Pre-Energization Requirements

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Energization Tests

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Evaluating the Results of Motor Commissioning for Acceptability or Unacceptability

28

WORK AID Work Aid 1: Procedure and Acceptable Values for Evaluatingthe Results of Motor Commissioning Compiled from SADP-P-113, NEMA MG-1, and Established Engineering Practices

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GLOSSARY

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Saudi Aramco DeskTop Standards



PRE-ENERGIZATION REQUIREMENTS Pre-energization requirements are the inspections and the tests that must be performed prior to the initial application of power to a new motor. The overall purpose of the pre-energization requirements is to verify that the motor can be safely energized with no danger to personnel or to equipment. The following pre-energization requirements will be discussed in this section: _Verification of Electrical Connections/Interlocks _Verification of Mechanical Integrity _Lubrication System Checks _Insulation Resistance (IR) and Polarization Index (PI) Checks _Air Gap Check _Verification of Protective Relay Setpoints _Phase Rotation Test Verification of Electrical Connections/Interlocks A verification of the electrical connections/interlocks that are associated with a motor is performed for the following reasons: _To ensure that all of the individual electrical components that are shown on the project electrical wiring diagrams and on the project elementary diagrams are actually installed. _To ensure that the power cable runs and that the power cable terminations are in accordance with the project drawings. _To ensure that all of the wired connections are accurate (e.g., the wires are labeled in accordance with the project drawings, and the wires are terminated at the locations that are specified on the project drawings) and are tight. _To ensure that electrical continuity, as specified in the project electrical wiring diagrams and in the project elementary diagrams, exists between all of the wired connections. _To ensure that electrical continuity exists across all of the control and the interlock contacts when the contacts are manually operated.


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Verification of Electrical Connections/Interlocks (Cont’d) The following inspections, checks, and tests must be performed to verify electrical connections/interlocks: _Visual Inspection _Torque Check _Resistance Test Before the visual inspection can be performed, the most recent revision of the project electrical wiring diagrams and the project elementary diagrams must be obtained. These diagrams are used to visually verify the following items through comparison of the actual installation to the installation that is specified in the drawings: _That the specified electrical components actually are installed. _That the power cable runs and the power cable terminations are correct. _That the wired connections are accurate. Torque checks are performed to verify that all of the wired connections (power and control) are tight. Torque checks are performed in the following way: an applicable tool (screwdriver, torque wrench, barrel nut driver) is placed on the connection hardware and the proper torque is subsequently applied to the connection hardware to verify that the connection is tight. Care should be taken in the performance of torque checks to ensure that excessive torque is not applied to the connection hardware. Resistance tests are performed to verify that electrical continuity exists between all of the wired connections. Resistance tests also are performed to ensure that electrical continuity exists across all of the control and the interlock contacts when the contacts are manually operated. The following major steps are involved in the performance of a resistance test to verify that electrical continuity exists between two points in a circuit: _A multimeter and copies of the project electrical wiring diagrams and the project elementary wiring diagrams must be obtained to perform the tests. _The project elementary wiring diagram is used to identify the various points in the motor circuit between which electrical continuity should exist. Because the continuity between numerous individual points (paths) must be verified, a highlighter should be used to mark, on the elementary wiring diagram, the paths that have been verified. _The project electrical wiring diagram is used to identify the physical location in the installed equipment that corresponds to the points that are identified on the project elementary wiring diagrams.


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Verification of Electrical Connections/Interlocks (Cont’d) _The leads of the multimeter are connected to the physical locations in the installed equipment that correspond to the first set of points between which electrical continuity should exist. _The resistance between the points to which the multimeter leads are connected is read on the scale of the multimeter. Proper electrical continuity normally is indicated by a resistance reading that is less than 1_. If the path between the points to which the multimeter leads are connected contains components such as relay coils or transformer windings, proper electrical continuity will be indicated by a resistance reading that approximately corresponds to the resistance of the components that are in the path. _The process of connecting of the multimeter leads and measuring resistance is repeated for the remaining points in the circuit between which electrical continuity should exist. Verification of Mechanical Integrity A verification of the mechanical integrity of a new motor is performed for the following reasons: _To ensure that there are no damaged parts, loose parts, or missing parts on the motor. _To ensure that all of the mechanical components of the motor freely operate. _To ensure that the general physical condition of the motor is satisfactory for operation. The verification of mechanical integrity is performed through a combination of visual and physical inspections. The visual inspection should include the following items: _A verification that all accessory equipment is installed and is properly aligned. _A verification that the motor is properly anchored and properly mounted. _A verification that there is no water damage or corrosion. _A verification that the motor is free from dust and from dirt.


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Verification of Mechanical Integrity (Cont'd) _A verification that all packing, shipping braces, blocking, shipping tags, or other equipment that could impede proper mechanical operation or proper electrical operation has been removed. _A verification that all screens, guards, and other protective devices are properly installed. The physical inspection should include the following items: _A verification that all mechanical parts that move are operable in accordance with the manufacturer's requirements. _A verification that the motor shaft freely rotates. Lubrication System Checks Lubrication system checks are performed to ensure that the motor bearings will be provided with proper lubrication upon energization of the motor. The items that are inspected in the performance of lubrication system checks are dependent on the type of lubrication system with which the motor is equipped. Motors can be equipped with the following types of lubrication systems: _Self-contained lubrication systems _External lubrication systems Most motors are equipped with self-contained lubrication systems. These systems use grease or oil to provide the required lubrication to the motor bearings. The lubrication system check that is performed on a self-contained lubrication system should consist of a visual inspection of the following items: _The motor installation records should be reviewed to ensure that the proper lubricant (grease or oil) was used to initially lubricate the bearings. _As applicable, the bearing cavity or the oil reservoir should be inspected to ensure that it contains the proper amount of lubrication. The bearing or the oil reservoir also should be inspected to ensure that it does not contain moisture. _If the bearings are equipped with dirt seals and/or dirt shields, these devices should be inspected to ensure that they are properly installed.


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Lubrication System Checks (Cont'd) _All of the components such as pipes, plugs, drains, and sightglasses should be inspected to ensure that these components are properly installed. Large motors can be equipped with external lubrication systems. These systems use an oil pump and associated oil pipes to provide the motor bearings with a continuous supply of lubrication. External lubrication systems usually contain the following major components: _An oil pump that is driven by the motor shaft or one that is driven by a separate motor. _An oil sump. _An oil filter. _The associated oil system pipes. _Oil system monitoring equipment such as oil flow indicators, oil pressure gauges, and oil temperature indicators. The lubrication system check that is performed on an external lubrication system should consist of the following major steps (if the lubrication system uses an oil pump that is driven by the motor shaft, the steps that are marked with an asterisk must be performed during the no-load run test): _The motor installation records should be reviewed to ensure that the oil sump was initially filled with the correct lubricant. _The level of oil in the oil sump should be checked to ensure that the level is in the normal operational band. _An oil sample should be drawn from the oil sump, and the oil sample should be checked to ensure that it does not contain water or foreign material. _A visual inspection of all of the oil system components should be performed to verify the mechanical integrity of the system. _The oil system should be started, and it should be allowed to heat up to the normal temperature of operation. While the oil system heat up is in progress, all of the components of the oil system should be inspected for leaks.*


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Lubrication System Checks (Cont'd) _After the system has reached the normal temperature of operation, the oil flow indicators and the oil pressure gauge should be checked to ensure that the indications are in the normal operational band.* _The motor and the oil system should be shut down, or if the oil system is equipped with a standby oil filter, the standby oil filter should be placed in service, and the oil filter should be inspected for foreign material.* Insulation Resistance (IR) and Polarization Index (PI) Checks The purpose of insulation resistance checks is to determine the integrity of the motor's insulation system. Insulation resistance checks consist of the megohmmeter test, the polarization index check, and the high potential (hi-pot) test. The sections that follow provide a more detailed discussion of the following topics: _Megohmmeter _High Potential Test Megohmmeter

The results of a megohmmeter test are used to determine whether a motor's insulation system has any gross defects and to calculate the polarization index. The polarization index provides a quantitative appraisal of the condition of a motor's insulation with respect to moisture and to other contaminants. This section will discuss the performance of megohmmeter tests on the following types of motors and motor components: _Induction Motors _Synchronous Motors _Bearing Insulation


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Insulation Resistance (IR) and Polarization Index (PI) Checks (Cont'd) Induction Motors - Figure 1 shows the Saudi Aramco Motor Test Record (Part One).

This test record contains the procedural steps that should be followed to perform a megohmmeter test on an induction motor. The test record is divided into the following sections and tables: _Preparation for Test _Test Procedure for Insulation Resistance (e.g., megohmmeter test) _Test Procedure for Polarization Index _Table I _Table II The Preparation for Test section provides the preliminary steps that must be performed prior to an insulation resistance test. The Test Procedure for Insulation Resistance section provides the procedural steps that must be followed to perform an insulation resistance test. This section also provides the equation that must be used to correct the value of insulation resistance that is obtained from the test for temperature. The Test Procedure for Polarization Index section provides the procedural steps and the equation for determination of the polarization index. Table I shows the test voltage that should be used in the performance of an insulation resistance test. The test voltage that should be used is dependent on the rated voltage of the motor. Table II shows the various values of the insulation resistance temperature coefficient (Kt). Kt is used in the equation for temperature correction of insulation resistance values.


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Insulation Resistance (IR) and Polarization Index (PI) Checks (Cont'd)

Saudi Aramco Motor Test Record (Part One) Figure 1


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Insulation Resistance (IR) and Polarization Index (PI) Checks (Cont'd) Synchronous Motors - Figure 2 shows the Saudi Aramco Motor Test Record (Part Two).

This portion of the test record contains the procedural steps that should be followed to perform a megohmmeter test on a synchronous motor. This portion of the test record is divided into the following major sections: _Procedure for Exciter and Rotor Insulation Test (e.g., megohmmeter test) _Procedure for Bearing Insulation Resistance Test _Rotating Rectifier _Air Gap _Notes The Procedure for Bearing Insulation Resistance Test section and the Air Gap section do not apply to the performance of megohmmeter tests on synchronous motors. These sections of the test record will be discussed later in this module. The Procedure for Exciter and Rotor Insulation Resistance Test section provides the procedural steps that must be followed to perform an insulation resistance test on a synchronous motor. The polarization index check for a synchronous motor should be performed through use of the test procedure for polarization index that previously was shown in Figure 1, except that the test voltage should be 500 volts. The Rotating Rectifier section provides the procedural steps that should be followed to perform an insulation resistance test on the rotating rectifier of a synchronous motor. This section also provides the procedural steps for performance of a resistance test on the rotating rectifier diodes to ensure that the diodes are properly connected. The Notes section applies both to induction and to synchronous motors. This section contains the minimum acceptable values for insulation resistance and for polarization index. This section also contains additional guidance for the performance of insulation resistance tests on motors in which the neutral point cannot be disconnected.


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Insulation Resistance (IR) and Polarization Index (PI) Checks (Cont'd)

Saudi Aramco Motor Test Record (Part Two) Figure 2


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Insulation Resistance (IR) and Polarization Index (PI) Checks (Cont'd) Bearing Insulation Resistance - A bearing insulation resistance test should be performed

on motors that have insulated bearings. The procedural steps that must be followed to perform a bearing insulation resistance test previously were shown in Figure 2. The minimum acceptable value of bearing insulation resistance is 200 k_. The preferred value of bearing insulation resistance is 1M_ or above. High-Potential Test

The high potential (hi-pot) test is performed to provide positive proof that a motor's insulation has sufficient voltage strength to ride out overvoltage surges. Before a hi-pot test can be performed on a motor, a megohmeter test must be performed to prove that the motor's insulation resistance and polarization index are above the minimum acceptable values. The following major steps are involved in the performance of a hi-pot test: _The maximum DC voltage for the test must be calculated through use of the following formula: Maximum Voltage = 85% {1.7(2 _ Rated Voltage + 1kV)} _The DC high potential test set must be connected between the motor phase leads and ground. _After the test set is connected, the initial test voltage, which is equal to 33% of the maximum test voltage, is applied to the motor. The initial test voltage is constantly held for ten minutes, and the leakage current, as read on the ammeter that is on the face of the high potential test set, is monitored. The value of leakage current should be recorded at the end of each one minute interval. _When the first ten minutes of the test is complete, the test voltage should be raised from the initial value of 33% to the maximum value in ten equal steps. After each step increase in voltage, the voltage should be held at the new level for a period of one minute, and the leakage current should be recorded at the end of each minute. The results of a hi-pot test are not compared to a specific value to determine whether the results are acceptable. Instead, the results of a hi-pot test are analyzed for trends that indicate whether the insulation has sufficient strength to ride out overvoltage surges. Figure 3 shows a graphic display of the typical results of hi-pot tests for both good and bad insulation. The graph that is shown in Figure 3A is for the first ten minutes of a hi-pot test. The curve that represents good insulation shows a steep rise in leakage current over the first one minute Saudi Aramco DeskTop Standards

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interval that is followed by a steady decrease in the value of leakage current over the remainder of the ten minute interval.


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Insulation Resistance (IR) and Polarization Index (PI) Checks (Cont'd) The curve that represents bad insulation shows a steady increase in the value of leakage current throughout the ten minute interval. Such a curve indicates unsatisfactory insulation, and the hi-pot test should be stopped. The graph that is shown in Figure 3B is for the last ten minutes of the hi-pot test. The curve that represents good insulation shows a slow, steady increase in the value of leakage current as the test voltage is raised from 33% to 100%. The curve that represents bad insulation shows a sharp upturn or knee when the test voltage is increased to the point at which the insulation starts to break down. A knee in the leakage current curve indicates unsatisfactory insulation, and the hi-pot test should be stopped.


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Typical Results of Hi-Pot Tests Figure 3


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Air Gap Check The radial air gap should be checked on motors that are rated at 5000 hp or above to ensure that the air gap is uniform and that it is within the manufacturer's specifications. An unequal air gap can cause unequal currents in the stator windings that will result in unequal heating of the stator windings. The unequal currents in the stator windings also can result in an unbalanced magnetic pull between the stator and the rotor, and an unbalanced magnetic pull increases the possibility of contact between the stator and the rotor while the motor is in operation. Such contact can result in catastrophic damage to the motor. The radial air gap should be checked at eight different points around the circumference of the stator. The radial air gap is checked through insertion of a feeler gauge between the rotor and the stator windings of a motor. The feeler gauge size that just bridges the gap between the rotor winding and the stator winding is the size of the radial air gap. Verification of Protective Relay Setpoints A verification of protective relay setpoints must be performed to ensure that the protective relays will actuate and that they will deenergize the motor when the parameters that are monitored by the relays reach an unacceptable value (e.g., the relay setpoints). The following is a summary of the major steps that must be performed to verify protective relay setpoints: _The manufacturer's technical literature for each relay that is to be tested should be obtained. The manufacturer's technical literature contains the time/current curves, the tolerances, and the special precautions/procedures that apply to the specific relays to be tested. _The source of the input signal to each of the protective relays must be checked to ensure that each relay senses the correct motor parameter. _Relay test apparatus such as AC power supplies, ammeters, phase shifters, variacs, phase angle meters, and electronic timers must be obtained. The test apparatus must be able to simulate the actual operational conditions under which each relay is designed to operate. The test apparatus also must be able to accurately indicate the point at which each relay actuates.


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Verification of Protective Relay Setpoints (Cont'd) _The appropriate test apparatus is connected to one of the relays, and then the test apparatus is operated so that it simulates the operational conditions under which the connected relay is designed to operate. After the relay operates, the following items should be verified: -

That the relay operated at the correct setpoint. That the target indicators and the seal-in units properly operated. That the contact that is used to deenergize the motor contactor or to open the motor circuit breaker properly operated.

This step must be repeated for each protective relay that is part of the motor protection scheme. Phase Rotation Test Phase rotation tests are performed to ensure that the motor will rotate in the correct direction and that the motor leads are properly marked to coincide with the power system leads. If the motor rotates in the wrong direction, damage can occur to the motor bearings and to the connected load. The phase rotation test is the final pre-energization requirement because this test actually is performed through energization of the motor. The phase rotation test consists of a visual verification that the motor leads are properly marked to coincide with the power system leads and that the motor shaft rotates in the correct direction. The phase rotation test is performed through a momentary application of power to the motor while the load is disconnected, and through observation of the direction of shaft rotation. If the shaft rotates in the wrong direction, the connection between two of the motor leads and two of the power system leads must be switched. After the leads are switched, the phase rotation test should be repeated to verify that the direction of shaft rotation has been corrected. After the verification is complete, the motor lead markers also should be switched.


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ENERGIZATION TESTS Energization tests are performed on a new motor to verify that the motor installation is free from defects, to verify that the motor operates within its design limits, and to establish baseline motor operational data. Before energization tests are performed on a motor, all of the discrepancies that were identified during the pre-energization tests must have been corrected. This section of the Module provides information on the following topics that are pertinent to energization tests: _No Load Run Test _Load Run Test No Load Run Test For an electric motor, a no load run test consists of the measurement of various operational parameters of the motor while the motor is in operation but before the motor is connected to the load that it was installed to drive. The no load run test is performed prior to connection of the motor to its load to ensure that the information that is obtained from the test only applies to the motor. If the information that is obtained from the test is unsatisfactory and if the test is conducted with the motor being connected to the load, the cause of the unsatisfactory condition would be more difficult to determine. Also, if a problem does exist with the motor, performance of the test with the motor being connected to the load would be more likely to aggravate the problem. The operational parameters that are measured during a no load run test vary with the type of motor to be tested. This section will discuss the no load run tests that are performed on the following types of motors: _Induction Motors _Synchronous Motors Before a no load run test is performed on a motor that is equipped with space heaters, the space heaters must be turned on and the space heater current must be measured. The space heater current is measured to verify that the space heaters properly operate (e.g., that there are no burned out units or loose connections). In order to ensure that condensation does not form inside of the motor when the motor cools off after the test, the space heaters must be operational before the no load run test is performed.


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No Load Run Test (Cont'd) Induction Motors

For an induction motor, the following operational parameters should be monitored during a no load run test: _Phase Current Balance _Voltage Balance _Vibration Level _RTD Readings for Bearings and Stator Windings Phase Current Balance - The phase current balance of induction motors is monitored

during the no load run test through measurement and comparison of the individual phase current values. The individual phase current values of properly designed threephase induction motors that are connected to balanced three-phase power sources should be equal. If the individual phase current values are not equal, one or more of the following problems can exist with the motor and/or the motor installation: _A high resistance connection in the motor circuit or in the motor supply circuit _A partial short-circuit or ground-fault in the motor circuit or in the motor supply circuit _An open in the motor circuit or in the motor supply circuit _A supply voltage unbalance The phase current balance of induction motors is monitored during the no load run test to verify that the above problems do not exist and to establish the baseline no load phase current values. If the cause of a phase current unbalance is not corrected and a motor is operated with unbalanced phase currents for prolonged periods of time, permanent motor damage can result. The mechanism through which unbalanced phase currents cause permanent damage is excessive heat. One of the individual phase current magnitudes will likely exceed the nameplate current rating in a motor that operates at or near full load with unbalanced phase currents. The phase current magnitude that exceeds the nameplate current rating will cause localized heating in the motor that may or may not be detected by the motor's protective devices. If the localized heating is not detected by the motor's protective devices, this heating eventually will result in damage to the motor's insulation.


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No Load Run Test (Cont'd) Voltage Balance - The voltage balance of the power source to which an induction motor

is connected is monitored through measurement and through comparison of the individual phase voltages of the power source during the no load run test. If the individual phase voltages of the power source are not equal, one of the following problems may exist: _An open in one phase of the power source _Unequal power source phase impedances The voltage balance of the power source to which the motor is connected is monitored during the no load run test to verify that the above problems do not exist. If the cause of a power source voltage unbalance is not corrected and a motor is operated from a power source that has unbalanced phase voltages, the unbalanced phase voltages will result in unbalanced phase currents. The unbalanced phase currents can result in permanent motor damage as previously discussed. The magnitude of the phase current unbalance that can result from operation of a motor that is connected to a power source that has unbalanced phase voltages is on the order of six to ten times the magnitude of the voltage unbalance. Vibration Level - The vibration levels of induction motors are monitored during the no

load run test through use of the permanently installed vibration monitoring equipment, or in cases where motors are not equipped with permanently installed vibration monitoring equipment, through use of portable vibration monitoring equipment. If the motor exhibits excessive levels of vibration, one of the following problems can exist with the motor and/or with the motor installation: _The motor is not properly balanced. _The motor is not properly mounted. _The motor shaft is bent. _The motor bearings are defective or are improperly installed. The vibration levels of induction motors are monitored during the no load run test to verify that the above problems do not exist and to establish the baseline no load vibration levels for the motor. If motors are operated with vibration problems, a variety of motor problems can result dependent on the severity of the vibrations. Minor vibrations cause a reduction in bearing life and an increase in the overall stress that is placed on the motor components. The increased stress that is placed on the motor components eventually can lead to fatigue failures. Severe vibrations can quickly cause catastrophic motor failures such as rotor contact with the stator.


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No Load Run Test (Cont'd) RTD Readings for Bearings and Stator Windings - RTD readings (temperature) for bearing

and stator windings are monitored during the no load run test through use of the permanently installed monitoring equipment. Because these readings are monitored under no load conditions, the readings should be significantly less than the full load limits. A high rate of bearing and/or stator temperature rise would indicate a serious problem with the lubrication system and/or the cooling system. The RTD readings for bearings and stator windings are monitored during the no load run test for the following reasons: _To verify that serious problems do not exist with the lubrication or with the cooling system. _To verify proper operation of the installed temperature monitoring equipment. _To establish baseline no load temperature values for the bearings and stator windings. Test Duration - The no load run test for an induction motor should last for

approximately four hours. The value of each parameter that is monitored during a no load run test should be recorded every 30 minutes. If the parameters that are being monitored have not reached steady state values after four hours, the test should be extended until the parameters stabilize. Synchronous Motors

For a synchronous motor, the following operational parameters should be monitored during a no load run test: _Phase Current Balance _Voltage Balance _Vibration Level _RTD Readings for Bearings and Stator Windings _Field Current _Power Factor and kVAR Control Phase Current Balance - The phase current balance of a synchronous motor is monitored

in the same way and for the same reasons as previously described for an induction motor.


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No Load Run Test (Cont'd) Voltage Balance - The voltage balance of a synchronous motor is monitored in the same

way and for the same reasons as previously described for an induction motor. Vibration Level - The vibration levels of a synchronous motor are monitored in the same

way and for the same reasons as previously described for an induction motor. RTD Readings for Bearings and Stator Windings - The RTD readings (temperatures) of the

bearing and the stator windings of a synchronous motor are monitored in the same way and for the same reasons as previously described for an induction motor. Field Current - Large synchronous motors have two separate fields: the exciter field and

the motor field. The exciter field current is the DC current that is supplied to the exciter of a synchronous motor. The motor field current is the rectified output of the exciter. The amount of motor field current that is produced by the exciter is controlled through variance of the exciter field current. The following field current parameters should be monitored during the no load run test of a synchronous motor: _The speed of the motor when DC current is first supplied to the exciter field (i.e., the exciter is excited). _The no load exciter field current. _The no load motor field current. The speed at which the exciter is excited is monitored through connection of an oscillograph to monitor the speed of the motor and the point at which the exciter contactor operates during the no load run test. The speed at which the exciter is excited must be correct because if the exciter is excited before the motor attains sufficient speed, the motor's rotor will not be able to synchronize with the stator field. If the rotor does not synchronize with the stator field, large pulsating torques will be produced, and these torques will cause excessive mechanical stresses to be placed on the motor's shaft. The no load exciter field current is monitored through use of the installed ammeter during the no load run test. The no load exciter field current is monitored to verify the proper setup and proper operation of the excitation control circuit.


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No Load Run Test (Cont'd) The no load motor field current is monitored through use of the installed ammeter during the no load run test. The no load motor field current is monitored to verify the proper operation of the AC exciter and the rotating rectifier. Power Factor and kVAR Control - The power factor and the kVAR of a synchronous

motor are directly related to each other, to the motor's excitation, and to the motor's load. When the load that is on the motor remains constant, a change in the motor's excitation should cause a corresponding change in the motor's power factor and in the motor's kVAR. If the motor's excitation is increased and the motor's load remains constant, the motor's power factor should become more "leading" and the motor should supply more kVAR (leading VAR's). If the motor's excitation is decreased and the motor's load remains constant, the motor's power factor should become less "leading" and the motor should supply less kVAR (leading VAR's). If the motor's excitation is continually decreased, the motor's power factor eventually will pass through "unity" and become "lagging." Correspondingly, when the power factor is at "unity," the motor should supply zero kVAR, and when the motor's power factor becomes "lagging," the motor should start to draw kVAR (lagging VAR's) from the power supply. The power factor and the kVAR of a synchronous motor are monitored through use of the installed power factor and kVAR meters during the no load run test. If the motor does not have a kVAR meter, an indication of kVAR can be obtained from the AC amperes of the motor. The power factor and the kVAR of a synchronous motor are monitored during the no load run test to verify the proper setup and the proper operation of the excitation control circuit. If the excitation control circuit does not supply sufficient excitation, the motor's power factor can become lagging, the motor can start to draw reactive power, and in cases of extremely low excitation, the rotor can lose synchronization. If the excitation control circuit supplies too much excitation, the motor's power factor can become excessively leading and the motor will supply excessive kVAR. Such conditions will cause the motor to overheat. Test Duration - The no load run test for a synchronous motor should last for

approximately four hours. The value of each parameter that is monitored during a no load run test should be recorded every 30 minutes. If the parameters that are being monitored have not reached steady state values after four hours, the test should be extended until the parameters stabilize.


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Load Run Test For an electric motor, a load run test consists of the measurement of various operational parameters of the motor while the motor is in operation and while it is connected to the load that it was installed to drive. The load run test should be conducted after all of the necessary repairs/adjustments that were identified during the no load run test have been completed. The operational parameters that are measured during a load run test vary with the type of motor to be tested. This section will discuss the load run tests that are performed on the following types of motors: _Induction Motors _Synchronous Motors Induction Motors

The following operational parameters should be monitored during a load run test for an induction motor: _Verify Motor Alignment _Phase Current Balance _Voltage Balance _Vibration Level _RTD Readings for Bearings and Stator Windings _Voltage Dip on Start _Acceleration Time _Test Duration Verify Motor Alignment - The motor alignment must be verified after the motor shaft is

coupled to the load shaft. This verification should be performed before the motor is started with the connected load. The motor alignment verification is performed to ensure that the following types of misalignment do not exist: _Angular misalignment _Parallel misalignment Angular misalignment is the amount by which the face of the motor half of the coupling is out of parallel with the face of the load half of the coupling. Angular misalignment can be checked through use of a dial indicator.


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Load Run Test (Cont'd) Parallel misalignment is the amount by which the centerline of the motor half of the coupling is offset from the centerline of the load half of the coupling. Parallel misalignment also can be checked through use of a dial indicator. The motor alignment must be verified before the motor is operated because any amount of misalignment will result in the placement of increased stresses on the bearings and the couplings. Such increased stresses will result in reduced bearing life and in reduced coupling life. Motor misalignment also will cause motor vibration levels to increase. An increase in motor vibration levels places additional stress on motor components such as mounting bolts and winding supports, and this additional stress can result in a premature failure of the motor. Phase Current Balance - The phase current balance is monitored during the load run test

of an induction motor in the same way and for the same reasons as previously described for the no load run test of an induction motor. The only change that should be noted during the load run test is an increase in the individual values of phase current because the motor is loaded. The variation (in percent) between the individual phase currents should remain the same. Voltage Balance - The voltage balance is monitored during the load run test of an

induction motor in the same way and for the same reasons as previously described for the no load run test of an induction motor. The only change that should be noted during the load run test is a possible decrease in the individual values of phase voltage because of supply system voltage droop under load. The variation (in percent) between the individual phase voltages should remain the same. Vibration Level - The vibration levels of induction motors again are monitored during the load run test through use of the permanently installed vibration monitoring equipment, or in cases where motors are not equipped with permanently installed vibration monitoring equipment, through use of portable vibration monitoring equipment. If the motor exhibits excessive levels of vibration during the load run test, one of the following problems may exist with the load or with the installation:

_The motor is not properly aligned with the load. _The load is not properly mounted. _The load shaft is bent. _The load bearings are defective or are improperly installed. _The installation produces mechanical resonance vibrations.


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Load Run Test (Cont'd) The vibration levels of induction motors are monitored during the load run test to verify that the above problems do not exist and to establish the baseline vibration levels for the motor under loaded conditions. If motor/load installation is operated with excessive levels of vibration, a variety of problems can result dependent on the severity of the vibrations. Minor vibrations cause a reduction in bearing life and an increase in the overall stress that is placed on the motor/load components. The increased stress that is placed on the motor/load components eventually can lead to fatigue failures. Severe vibrations quickly can cause catastrophic motor/load failures. RTD Readings for Bearings and Stator Windings - The RTD readings for bearings and for

stator windings are monitored during the load run test of an induction motor in the same way and for the same reasons as previously described for the no load run test of an induction motor. The changes that should be noted during the load run test are faster rates of temperature increase and higher steady state temperatures. These changes occur because the motor is loaded. Voltage Dip on Start - The amount with which the terminal voltage of an induction motor

drops when the motor is started is monitored at the start of the load run test. As previously explained in Module EEX 203.03, all motors cause the terminal voltage of the power source to drop by some amount. The actual amount of voltage drop that occurs will depend on the following factors: _The size (hp/kW) of the motor. _The minimum short-circuit kVA of the power source. _The method (full- or reduced-voltage) that is used to start the motor. _The number of other loads that are in operation when the motor is started. The calculation of voltage dip is performed when the initial specifications for a new motor are determined. The calculation is used to determine the method that should be used to start the motor. The actual voltage dip on start is monitored at the start of the load run test to verify that the actual drop in voltage does not exceed the allowable drop in voltage. If the actual drop in voltage exceeds the allowable drop in voltage, the cause of the excessive voltage drop must be identified and corrected before the motor is placed in normal operation. Acceleration Time - The acceleration time of an induction motor also is monitored at the

start of the load run test. The acceleration time of a motor is the elapsed time (in seconds) between the point at which power is applied to the motor and the point at which the load reaches normal operational speed.


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Load Run Test (Cont'd) The acceleration time of an induction motor must be monitored at the start of the load run test to verify that the actual acceleration time is less than the maximum allowable acceleration time. If the actual acceleration time exceeds the maximum allowable acceleration time, the motor can overheat because of the extended length of time with which the motor is subjected to starting current. Test Duration - The load run test for an induction motor should last for approximately

four hours. The value of the following parameters that are monitored during the load run test should be recorded every 30 minutes: _Phase current balance _Voltage balance _Vibration levels _RTD readings for bearings and stator windings If the parameters that are monitored have not reached steady state values after four hours, the test should be extended until the parameters stabilize. Synchronous Motors

The following operational parameters should be monitored during a load run test for a synchronous motor: _Verify Motor Alignment _Phase Current Balance _Voltage Balance _Vibration Level _RTD Readings for Bearings and Stator Windings _Voltage Dip on Start _Acceleration Time _Field Current _Power Factor and kVAR Control _Test Duration Verify Motor Alignment - The motor alignment for synchronous motors is verified in the

same way and for the same reasons as previously described for an induction motor load run test.


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Load Run Test (Cont'd) Phase Current Balance - The phase current balance is monitored during the load run test

of a synchronous motor in the same way and for the same reasons as previously described for the no load run test of a synchronous motor. The only change that should be noted during the load run test is an increase in the individual values of phase current because the motor is loaded. The variation (in percent) between the individual phase currents should remain the same. Voltage Balance - The voltage balance is monitored during the load run test of a

synchronous motor in the same way and for the same reasons as previously described for the no load run test of a synchronous motor. The only change that should be noted during the load run test is a possible decrease in the individual values of phase voltage because of supply system voltage droop under load. The variation (in percent) between the individual phase voltages should remain the same. Vibration Level - The vibration levels are monitored during the load run test of a

synchronous motor in the same way and for the same reasons as previously described for the load run test of an induction motor. RTD Readings for Bearing and Stator Windings - The RTD readings for bearings and for

stator windings are monitored during the load run test of a synchronous motor in the same way and for the same reasons as previously described for the no load run test of a synchronous motor. The changes that should be noted during the load run test are faster rates of temperature increase and higher steady state temperatures. These changes occur because the motor is loaded. Voltage Dip on Start - The amount with which the terminal voltage of a synchronous

motor drops when the motor is started is monitored at the start of the load run test for the same reasons as previously described for the load run test of an induction motor. Acceleration Time - The acceleration time of a synchronous motor is monitored at the

start of the load run test for the same reasons as previously described for the load run test of an induction motor. Field Current - The following field current parameters should be monitored during the

load run test of a synchronous motor: _The speed of the motor when DC current is first supplied to the exciter field (e.g., the exciter is excited). _The full load exciter field current. _The full load motor field current. Saudi Aramco DeskTop Standards

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Load Run Test (Cont'd) The speed at which the exciter is excited is monitored through connection of an oscillograph to monitor the speed of the motor and the point at which the exciter contactor operates during the load run test. The speed at which the exciter is excited must be correct because if the exciter is excited before the motor attains sufficient speed, the motor's rotor will not be able to synchronize with the stator field. If the rotor does not synchronize with the stator field, large pulsating torques will be produced, and these torques will cause excessive mechanical stresses to be placed on the motor's shaft. The full load exciter field current is monitored through use of the installed ammeter during the load run test. The full load exciter field current is monitored to verify the proper setup and proper operation of the excitation control circuit. The full load motor field current is monitored during the load run test through use of the installed ammeter. The full load motor field current is monitored to verify the proper operation of the AC exciter and the rotating rectifier. Power Factor and kVAR Control - The power factor and the kVAR of a synchronous

motor are monitored through use of the installed power factor and kVAR meters during the load run test. If the motor does not have a kVAR meter, an indication of kVAR can be obtained from the AC amperes of the motor. The power factor and the kVAR of a synchronous motor are monitored during the load run test to verify the proper setup and the proper operation of the excitation control circuit. If the excitation control circuit does not supply sufficient excitation, the motor's power factor can become lagging, the motor can start to draw reactive power, and in cases of extremely low excitation, the rotor can lose synchronization. If the excitation control circuit supplies too much excitation, the motor's power factor can become excessively leading, and the motor will supply excessive kVAR. Such conditions will cause the motor to overheat. Test Duration - The load run test for a synchronous motor should last for approximately

four hours. The value of the following parameters that are monitored during the load run test should be recorded every 30 minutes:


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Load Run Test (Cont'd) _Phase current balance _Voltage balance _Vibration levels _RTD readings for bearings and stator windings _Field current (exciter field and motor field) _Power factor and kVAR control If the parameters that are monitored have not reached steady state values after four hours, the test should be extended until the parameters stabilize.


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EVALUATING THE RESULTS OF MOTOR COMMISSIONING FOR ACCEPTABILITY OR UNACCEPTABILITY The final aspect of directing the startup and commissioning of electric motors is to evaluate the results of the commissioning for acceptability or unacceptability. To aid in the performance of the evaluation, the results of the motor commissioning are recorded on standardized commissioning forms as the individual inspections, checks, and tests are completed. To perform the evaluation, the Electrical Engineer must compare the actual results against the acceptable results to determine whether the motor is acceptable or unacceptable. The sections that follow provide information on the following topics that are pertinent to evaluating the results of motor commissioning for acceptability or unacceptability: _Motor Commissioning Form _Evaluating the Results of Induction Motor Commissioning _Evaluating the Results of Synchronous Motor Commissioning Motor Commissioning Form The purpose of a motor commissioning form is to provide a single, comprehensive record of the pertinent data that is collected when a new motor is commissioned. The motor commissioning form is divided into the following major sections: _Motor Identification Data _Pre-Energization Data _No Load Test Run Data _Load Run Test Data The motor identification data section is on page one of the motor commissioning form. Page one of the motor commissioning form is shown in Figure 4. This section provides a place to record information such as the make, type, serial number, ratings, and plant. This information can be used to positively identify this motor from other similar motors. This information also can be used to aid in the determination of which inspections, checks, and tests should have been performed. The pre-energization data section also is on page one of the motor commissioning form. This section provides a place to record the results of each of the pre-energization inspections, checks, and tests that were previously described in this module. The results that are recorded in this section are used in the evaluation of acceptability or unacceptability. The results that are recorded in this section also are used as the baseline data for future trend analysis.


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Motor Commissioning Form (Cont'd)

Motor Commissioning Form (Page One) Figure 4 Saudi Aramco DeskTop Standards

31



Motor Commissioning Form (Cont'd) The no load run test data section is on page two of the motor commissioning form. Page two of the motor commissioning form is shown in Figure 5. This section provides a place to record the values of each of the no load run test parameters that were previously described in this module. The values that are recorded in this section are used in the evaluation of acceptability or unacceptability. The results that are recorded in this section also are used as the baseline data for future trend analysis.


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Motor Commissioning Form (Cont'd)

Motor Commissioning Form (Page Two) Figure 5


33



Motor Commissioning Form (Cont'd) The load run test data section is on page three of the motor commissioning form and is shown in Figure 6. This section provides a place to record the values of each of the load run test parameters that were previously described in this module. The values that are recorded in this section are used in the evaluation of acceptability or unacceptability. The results that are recorded in this section also are used as the baseline data for future trend analysis.


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Motor Commissioning Form (Page Three) Figure 6


35



Evaluating the Results of Induction Motor Commissioning The procedure and the acceptable values for evaluating the results of motor commissioning are located in Work Aid 1. This section of the Module will provide a brief explanation of how to use the procedure and the acceptable values that are located in Work Aid 1 to evaluate the results of induction motor commissioning. Example Evaluation

Figure 7A, Figure 7B, and Figure 7C show the results of the inspections, checks, and tests that were performed to commission a hypothetical induction motor. From the procedure that is located in Work Aid 1, the first step in the evaluation is to review the motor identification data to determine the type and the size of the motor. Figure 7A shows that the motor type is induction and that the motor size is 3000 hp (2200 kW). The motor type and the motor size are used to determine whether all of the applicable inspections, checks, and tests were performed on the motor. Because this motor is a 3000 hp induction motor, the following inspections, checks, and tests should have been performed: _Inspection/check of electrical connections/interlocks _Inspection/check of mechanical integrity _Inspection/check of lubrication system _Phase to ground, phase to phase, and bearing insulation resistance readings _High potential test _Inspection/check of protective relays _Phase rotation test _No load run test that monitored the following parameters Phase current Phase voltage % voltage unbalance Bearing vibration Bearing, ambient, and winding temperatures _Load run test that monitored the following parameters Inspection/check of motor alignment Phase current Phase voltage % voltage unbalance Bearing vibration Bearing, ambient, and winding temperature Voltage dip on start Acceleration time


36



Evaluating the Results of Induction Motor Commissioning (Cont'd) Figures 7A, 7B, and 7C show that all of the applicable inspections, checks, and tests were performed on this motor. Because all of the applicable inspections, checks, and tests were performed, the next step of the procedure that is located in Work Aid 1 is to compare the pre-energization data with the acceptable values to determine whether the pre-energization data are acceptable. The acceptable values to which the pre-energization data are compared also are located in Work Aid 1. Through comparison of the data that are shown in Figure 7A with the acceptable values for pre-energization data that are located in Work Aid 1, the determination can be made that all of the pre-energization data for the motor are acceptable. Because all of the pre-energization data for the motor are acceptable, the next step of the procedure that is located in Work Aid 1 is to compare the no load run test data with the acceptable values to determine whether the no load run test data are acceptable. The acceptable values to which the no load run test data are compared also are located in Work Aid 1. Through comparison of the data that are shown in Figure 7B with the acceptable values for no load run test data that are located in Work Aid 1, the determination can be made that all of the no load run test data for the motor are acceptable. Because all of the no load run test data for the motor are acceptable, the next step of the procedure that is located in Work Aid 1 is to compare the load run test data with the acceptable values to determine whether the load run test data are acceptable. The acceptable values to which the load run test data are compared also are located in Work Aid 1. Through comparison of the data that are shown in Figure 7C with the acceptable values for load run test data that are located in Work Aid 1, the determination can be made that the results of the motor commissioning are acceptable.


37



Evaluating the Results of Induction Motor Commissioning (Cont'd)

Example Motor Commissioning Form (Page One) Figure 7A


38




Example Motor Commissioning Form (Page Two) Figure 7B


39




Example Motor Commissioning Form (Page Three) Figure 7C Saudi Aramco DeskTop Standards

40



Evaluating the Results of Synchronous Motor Commissioning The procedure and the acceptable values for evaluating the results of motor commissioning are located in Work Aid 1. This section of the Module will provide a brief explanation of how to use the procedure and the acceptable values that are located in Work Aid 1 to evaluate the results of synchronous motor commissioning. Example Evaluation

Figure 8A, Figure 8B, and Figure 8C show the results of the inspections, checks, and tests that were performed to commission a hypothetical synchronous motor. From the procedure that is located in Work Aid 1, the first step in the evaluation is to review the motor identification data to determine the type and the size of the motor. Figure 8A shows that the motor type is synchronous and that the motor size is 15000 hp (11300 kW). The motor type and the motor size are used to determine whether all of the applicable inspections, checks, and tests were performed on the motor. Because this motor is a 15000 hp synchronous motor, the following inspections, checks, and tests should have been performed: _Inspection/check of electrical connections/interlocks _Inspection/check of mechanical integrity _Inspection/check of lubrication system _Phase to ground and phase to phase insulation resistance readings _Exciter winding to ground insulation resistance reading _Rotor winding to ground insulation resistance reading _Rotating rectifier to ground insulation resistance reading _Bearing insulation resistance readings _High potential test _Rotating rectifier diode check _Air gap check _Inspection/check of protective relays _Phase rotation test _No load run test that monitored the following parameters Phase current Phase voltage % voltage unbalance Bearing vibration Bearing, ambient, and winding temperatures % Ns when excited Exciter and motor field currents Power factor Reactive power


41



Evaluating the Results of Synchronous Motor Commissioning (Cont'd) _Load run test that monitored the following parameters Inspection/check of motor alignment Phase current Phase voltage % voltage unbalance Bearing vibration Bearing, ambient, and winding temperature Voltage dip on start Acceleration time % Ns when excited Exciter and motor field currents Power factor Reactive power Figures 8A, 8B, and 8C show that all of the applicable inspections, checks, and tests were performed on this motor. Because all of the applicable inspections, checks, and tests were performed, the next step of the procedure that is located in Work Aid 1 is to compare the pre-energization data with the acceptable values to determine whether the pre-energization data are acceptable. The acceptable values to which the pre-energization data are compared also are located in Work Aid 1. Through comparison of the data that are shown in Figure 8A with the acceptable values for pre-energization data that are located in Work Aid 1, the determination can be made that all of the pre-energization data for the motor are acceptable. Because all of the pre-energization data for the motor are acceptable, the next step of the procedure that is located in Work Aid 1 is to compare the no load run test data with the acceptable values to determine whether the no load run test data are acceptable. The acceptable values to which the no load run test data are compared also are located in Work Aid 1. From a review of the acceptable values for no load run test data that are located in Work Aid 1, the acceptable values for the following parameters must be obtained from the manufacturer's technical manual: _% Ns when excited _Exciter field current _Motor field current _Power factor


42



Evaluating the Results of Synchronous Motor Commissioning (Cont'd) For this example evaluation, the following are the acceptable values for these parameters from the manufacturer's technical manual: _% Ns when excited should be a minimum of 98%. _No load exciter field current should be approximately 1.0 to 1.2 amps. _No load motor field current should be approximately 145 amps. _The design power factor is .9 leading. Through comparison of the data that are shown in Figure 8B with the acceptable values for no load run test data that are located in Work Aid 1, the determination can be made that all of the no load run test data for the motor are acceptable. Because all of the no load run test data for the motor are acceptable, the next step of the procedure that is located in Work Aid 1 is to compare the load run test data with the acceptable values to determine whether the load run test data are acceptable. The acceptable values to which the load run test data are compared also are located in Work Aid 1. From a review of the acceptable values for no load run test data that are located in Work Aid 1, the acceptable values for the following parameters must be obtained from the manufacturer's technical manual: _Acceleration time _% Ns when excited _Exciter field current _Motor field current _Power factor For this example evaluation, the following are the acceptable values for these parameters from the manufacturer's technical manual: _Acceleration time should be approximately 6 to 7 seconds. _% Ns when excited should be a minimum of 98%. _The rated exciter field current is 4.3 amps. _The rated motor field current is 490. _The design power factor is .9 leading. Through comparison of the data that are shown in Figure 8C with the acceptable values for load run test data that are located in Work Aid 1, the determination can be made that the results of the motor commissioning are acceptable.


43



Evaluating the Results of Synchronous Motor Commissioning (Cont'd)

Example Motor Commissioning Form (Page One) Saudi Aramco DeskTop Standards

44



Figure 8A


45




Example Motor Commissioning Form (Page Two) Figure 8B


46




Example Motor Commissioning Form (Page Three) Figure 8C Saudi Aramco DeskTop Standards

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WORK AID 1: PROCEDURE AND ACCEPTABLE VALUES FOR EVALUATING THE RESULTS OF MOTOR COMMISSIONING COMPILED FROM SADP-P-113, NEMA MG-1, AND ESTABLISHED ENGINEERING PRACTICES Work Aid 1 is designed to help the Participants complete Exercise 1. Procedure 1.

Review the motor identification data to determine the type and the size of the motor.

2.

Determine whether all of the applicable inspections, checks, and tests have been performed. This determination is based on the type and the size of the motor.

2A.

If all of the inspections, checks, and tests have not been performed, the results are unacceptable.

2B.

If all of the inspections, checks, and tests have been performed, continue with step three of this procedure.

3.

Compare the pre-energization data with the acceptable values for this data to determine whether the pre-energization data are acceptable.

3A.

If all of the pre-energization data are not within the acceptable values, the results are unacceptable.

3B.

If all of the pre-energization data are within the acceptable values, continue with step four of this procedure.

4.

Compare the no load run test data with the acceptable values for this data to determine whether the no load run test data are acceptable.

4A.

If all of the no load run test data are not within the acceptable values, the results are unacceptable.

4B.

If all of the no load run test data are within the acceptable values, continue with step five of this procedure.

5.

Compare the load run test data with the acceptable values for this data to determine whether the load run test data are acceptable.


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WORK AID 1 (Cont'd) 5A.

If all of the load run test data are not within the acceptable values, the results are unacceptable.

5B.

If all of the load run test data are within the acceptable values, the results of the motor commissioning are acceptable.

Acceptable Values for Pre-Energization Data Inspection/Check of Electrical Connection/Interlocks

The acceptable results for this inspection/check are that the inspection/check was satisfactorily completed. Satisfactory completion is indicated by an "X" in the YES column. Inspection/Check of Mechanical Integrity

The acceptable results for this inspection/check are that the inspection/check was satisfactorily completed. Satisfactory completion is indicated by an "X" in the YES column. Inspection/Check of Lubrication System

The acceptable results for this inspection/check are that the inspection/check was satisfactorily completed. Satisfactory completion is indicated by an "X" in the YES column. Insulation Resistance Readings

The acceptable values of insulation resistance only apply to insulation resistance readings that have been temperature corrected to 50oC. Before the temperature corrected insulation resistance readings are evaluated for acceptability or unacceptability, these values must be verified through use of the following formula and table: Rc = Kt _ Rt Where:

Rc is the insulation resistance corrected to 50oC. Rt is the direct insulation resistance reading. Kt is the insulation resistance temperature coefficient from the following table:


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Winding Temp. Kt

10o

20 o

30 o

40o

50o

60o

70o

80o

90o

100o

110o

.06

.12

.25

.5

1

2

4

8

16

32

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WORK AID 1 (Cont'd) The following are the minimum acceptable temperature corrected values of insulation resistance: Windings - Minimum acceptable

Voltage

Min. IR (M_)

4,000

13,200 5.5

460

2,400 1.5

15 3.5

Bearings - Minimum acceptable value is 200 k_, but > 1 M_ is preferred Polarization Index

Before the calculated values of polarization index can be evaluated, these calculated values must be verified through use of the following formula: The minimum acceptable value of polarization index for Class B and for Class F insulation is 2.0; however, polarization index values of 2.5 to 3.0 are preferred. High Potential Test

Before the results of the high potential test can be evaluated, the maximum and the initial test voltages that were used must be verified through use of the following formula: Maximum Voltage = 85%{1.7(2 _ Rated Voltage + 1 kV)} Initial Voltage = 33%(Maximum Voltage)


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The following are the acceptable results of a high potential test: The microamperes leakage current should decrease in value during the initial ten minutes of the test at 33% test voltage. The microamperes leakage current should show a steady rise for the remainder of the test until the maximum test voltage is reached.


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WORK AID 1 (Cont'd) A steady-state or rising value during the initial ten minutes of the test indicates poor insulation and, as a result, the insulation should be rejected. A sharp or an exponential rise in leakage current during the step voltage changes and prior to the application of the maximum test voltage also indicates poor insulation and, as a result, the insulation should be rejected. Rotating Rectifier Diode Check

The exact values of diode resistance vary from one diode to another diode. For purposes of motor commissioning, the acceptable values of diode resistance are a low resistance in the forward direction and a high resistance in the reverse direction. Air Gap Check

The minimum acceptable values for radial air gap are shown in the following table: Motor Rating kW H.P. (NEMA) 601 - 900 801 - 1250 901 -1350 1250 - 1750 1350 - 2000 1751 - 2500 2001 - 2900 2501 - 4000 2901 and up 4001 and up

Minimal Radial Air Gap mm (mil) 3.4 134 3.6 142 3.9 154 3.9 154 4.6 181

Inspection/Check of Protective Relays

The acceptable results for this inspection/check are that the inspection/check was satisfactorily completed. Satisfactory completion is indicated by an "X" in the YES column. Phase Rotation Test

The acceptable results for this test are that the test was satisfactorily completed. Satisfactory completion is indicated by an "X" in the YES column.


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WORK AID 1 (Cont'd) Acceptable Values for No Load Run Test Data Phase Current

The maximum phase current values normally range from five to seven times the full load current of the motor when the motor is started under loaded conditions. The actual phase current values when the motor is started under no load conditions should be below this range and, in no case, can the values exceed this range. The running values of phase current should be approximately equal to and should be less than the full load nameplate current rating. Phase Voltage

The individual phase voltages (A-B, B-C, and A-C) should be equal to the nameplate voltage rating _10%. Percent Voltage Unbalance

Before the percent voltage unbalance can be evaluated, the percent voltage unbalance calculation must be verified through use of the following formula: %VU = 100(Vd / Vavg) Where:

%VU is the percent voltage unbalance. Vd is the maximum phase voltage deviation (VA-B, VB-C, or VA-C minus Vavg, whichever yields the highest deviation). Vavg is the average of the individual phase voltages.

The maximum allowable percent voltage unbalance cannot exceed 1% for continuous operation. A percent voltage unbalance of 1.5% is acceptable for periods of time that are less than three minutes. Vibration Levels

The maximum allowable vibration levels for horizontal motors that are equipped with proximity probes are as follows:


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WORK AID 1 (Cont'd) Motor Speed (RPM) 3600 1800 1200 or less

Max. Vibration Level (Mils) 2.0 2.5 3.0

The maximum allowable vibration level for vertical and for horizontal motors that are equipped with seismic velocity transducers is 4.6 mm/s. Winding Temperature

The maximum winding temperature of a motor with Class B or with Class F insulation is 125oC at full load. This temperature is based on not exceeding the design temperature rise of Class B insulation when the ambient temperature is 50oC. The actual temperature that is measured during the no load run test should be significantly lower. Bearing Temperature

The maximum allowable bearing temperature of a motor that is operating at full load is 90oC or is 40oC above the ambient temperature, whichever temperature is lower. The actual temperature that is measured during the no load run test should be significantly lower. % Ns When Excited

The manufacturer's technical manual should be consulted for the minimum speed at which excitation should be applied to a given synchronous motor. If the manufacturer's technical manual is not available, the general thumbrule that is used is that excitation should not be applied until a synchronous motor reaches 97% to 98% of its rated synchronous speed. Exciter Field Current

The manufacturer's technical manual must be consulted to obtain the acceptable value of no load exciter field current for a given synchronous motor. Motor Field Current

The manufacturer's technical manual must be consulted to obtain the acceptable value of no load motor field current for a given synchronous motor. WORK AID 1 (Cont'd) Power Factor


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Synchronous motors are designed to operate at power factors that range from 0 to 0.8 leading. The manufacturer's technical manual must be consulted for the design power factor of a given synchronous motor. The actual power factor should be equal to the design power factor when the excitation control circuit is in automatic. Automatic is the normal mode of excitation control. Reactive Power (kVAR)

The maximum reactive power that a synchronous motor can supply is dependent upon the power factor at which the motor is operating. The maximum reactive power at a given power factor can be calculated through use of the following equation: kVAR = kVA _ sin{cos-1(pf)} The actual reactive power that is supplied by the motor should be consistent with the load that is on the motor and the power factor at which the motor is operating. Acceptable Values for Load Run Test Data Inspection/Check of Motor Alignment

The acceptable results for this inspection/check are that the inspection/check was satisfactorily completed. Satisfactory completion is indicated by an "X" in the YES column. Phase Current

When a motor is started under loaded conditions, the maximum phase current values should range from five to seven times the full load current of the motor. The running values of phase current should be approximately equal to each other and to the full load nameplate current rating. Phase Voltage

The individual phase voltages (A-B, B-C, and A-C) should be equal to the nameplate voltage rating _10%. Percent Voltage Unbalance

Before the percent voltage unbalance can be evaluated, the percent voltage unbalance calculation must be verified through use of the following formula:


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WORK AID 1 (Cont'd) %VU = 100(Vd / Vavg) Where:

%VU is the percent voltage unbalance. Vd is the maximum phase voltage deviation (VA-B, VB-C, or VA-C minus Vavg, whichever yields the highest deviation). Vavg is the average of the individual phase voltages.

The maximum allowable percent voltage unbalance cannot exceed 1% for continuous operation. A percent voltage unbalance of 1.5% is acceptable for periods of time that are less than three minutes. Vibration Levels

The maximum allowable vibration levels for horizontal motors that are equipped with proximity probes are as follows: Motor Speed (RPM) 3600 1800 1200 or less

Max. Vibration Level (Mils) 2.0 2.5 3.0

The maximum allowable vibration level for vertical and for horizontal motors that are equipped with seismic velocity transducers is 4.6 mm/s. Winding Temperature

The maximum winding temperature of a motor with Class B or with Class F insulation is 125oC at full load. This temperature is based on not exceeding the design temperature rise of Class B insulation when the ambient temperature is 50oC. Bearing Temperature

The maximum allowable bearing temperature of a motor that is operating at full load is 90oC or is 40oC above the ambient temperature, whichever temperature is lower.


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WORK AID 1 (Cont'd) Voltage Dip on Start (%)

The maximum voltage dip on start normally is limited to 15%. If an analysis of the other components of the power system shows that these components will not be adversely affected by a larger voltage dip, a voltage dip that is in excess of 15% may be permissible. Acceleration Time (Sec)

The manufacturer's technical manual should be consulted to obtain the design acceleration time of a given motor. If the manufacturer's technical manual is not available, the general thumbrule is that most motors should accelerate to rated speed within ten seconds. % Ns When Excited

The manufacturer's technical manual should be consulted for the minimum speed at which excitation should be applied to a given synchronous motor. If the manufacturer's technical manual is not available, the general thumbrule that is used is that excitation should not be applied until a synchronous motor reaches 97% to 98% of its rated synchronous speed. Exciter Field Current

The manufacturer's technical manual must be consulted to obtain the acceptable value of full load exciter field current for a given synchronous motor. Motor Field Current

The manufacturer's technical manual must be consulted to obtain the acceptable value of full load motor field current for a given synchronous motor. Power Factor

Synchronous motors are designed to operate at power factors that range from 0 to 0.8 leading. The manufacturer's technical manual must be consulted for the design power factor of a given synchronous motor. The actual power factor should be equal to the design power factor when the excitation control circuit is in automatic. Automatic is the normal mode of excitation control. Reactive Power (kVAR)

The maximum reactive power that a synchronous motor can supply is dependent upon the power factor at which the motor is operating. The maximum reactive power at a given power factor can be calculated through use of the following equation:


57



WORK AID 1 (Cont'd) kVAR = kVA _ sin{cos-1(pf)} The actual reactive power that is supplied by the motor should be consistent with the load that is on the motor and the power factor at which the motor is operating.


58



GLOSSARY angular misalignment

The amount by which the face of the motor half of the coupling is out of parallel with the face of the load half of the coupling.

insulation resistance

The amount of opposition to the flow of electric current that is offered by an insulation.

parallel misalignment

The amount by which the centerline of the motor half of the coupling is offset from the centerline of the load half of the coupling.

polarization index

The ratio of the insulation resistance of a machine winding measured at one minute after the voltage is applied divided into the measurement after ten minutes.

radial air gap

The distance between the rotor windings and stator windings of a motor.

reactive power

The product of the voltage, the current, and the cosine of the phase angle that is between the voltage and the current.


59

Saudi Aramco Engineering Standards-Electrical-Commissioning

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