Miniature Circuit Breaker Sizing _ Electrical Engineering Centre

iniat iniatu ure Circu Circuit Break Breaker er Sizin Sizing g | Elect Electrical rical Eng Enginee ineerin ring g Cen Centre tre

http:/ ttp://www /www.e .elec lectr tricn icneu euttron.c ron.com om/cir /circu cuit it-br -brea eak ker/min er/miniat iatu ure-circ re-circu uit-br it-brea eak k... ...

Home About Video Glossary Electrical Formul Formulas as Search Results Site map 04 February 2011 ~ 6 Comments

Circuit Breaker

0

Circuit Breaker Lockouts www.reecesafety.co.uk Complete range of locking devices to fit MCB, Circuit Breakers 3 Phase Power Monitor Monitor www.london-electronics.com Windows touch-screen to uch-screen power monitor and data logger logger with 4Gb capacity capac ity Electric Power Blogs www.energyblogs.com Read (and contribute) blogs blogs about electric elect ric power industry. motor soft starter wwww.wanzhou.com.cn high quality soft starter supplier 10 years experiences on motor start

1 f9

When we design or build a electrical installation,we must know how to choose the suitable circuit breaker for the any application that we design.For design.For electrician,this is compulsory knowledge.So here i want share my little knowledge about circuit breaker sizing method method.. This calculation for sizing the miniature circuit breaker.For breaker .For other circuit breaker likes MCCB,ACB,V MCCB ,ACB,VCB,OCB CB,OCB and etc,it have a additional factor and calculation that we must consider.For that i will discuss it in my next post…so this time i want explain the simple way how to sizing the miniature circuit breaker breaker..

8/3/2011 2 42 PM

iniature Circuit Breaker Sizing | Electrical Engineering Centre

http://www.electricneutron.com/circuit-breaker/miniature-circuit-break...

Why it so important? Ok..it have many reason as below : For electrical safety purpose To not over cost to purchase circuit breaker when we over sizing it. or not suitable To prevent the equipment from damage before it can use it. To easy when we want purchase the mcb,because we have all detail information about it. To make the design matter more effective and faster to complete.

How to select a suitable MCB for the application? we must focus in 3 main points to choose a right MCB for electrical circuit :1) Ampere rating ( In ) 2) Short circuit breaking capacity ( If ) 3) Application type

Calculation for Miniature circuit breaker ( MCB ) sizing Example : We want install 1 unit single phase motor.full load ampere is 20 ampere. Power supply 240VAC,50 Hz 1) Ampere Rating ( In )

Formula : In = 0.25 x Iz In = ampere rating

Iz = Load ampere

Calculation : In = 0.25 x 20 ampere In = 25 ampere x 0.25 ( safety factor ) In = 31.25 Ampere Refer the ampere rated in technical data for MCB from manufacture From the technical data,we selected the ampere rated for MCB is : 32 ampere

2 f9

8/3/2011 2 42 PM



2) Short circuit breaking capacity ( If )

Formula : If = V / 0.276 (R cable) If = short circuit breaking capacity V = Voltage R cable = resistance cable ( 0.276 ) Calculation :If = 240 / 0.276 If = 870 ampere From the answer,we can decide to select rating for one ( 1 ) kA 3) Application type.

From application,it state the single phase motor,so we can choose TYPE C for MCB.It for general application and for small motor.Please refer the table below for MCB type for the application. * For more detail,please refer the manufacture Technical data / user manual or contact the supplier. ABB MCB Technical data MCB Type,Instant trip and Application table —————————————————————————-

1

2.7 – 4 In

B

3 – 5 In

Domestic and commercial

————————————————————————— 2

4 – 7 In

C

5 – 10 In

3

General use,small motor

7 – 10 In

————————————————————————— D

10 – 20 In

4

10 – 50 In

High in rush equipment

—————————————————————————K

Frequent short duration

—————————————————————————Z

Semiconductor devices

—————————————————————————-

f9

8/3/2011 2 42 PM



So…the conclusion from the calculation,we get the specification for MCB t o install on our application :1) Rated ampere is : 32 ampere 2) Short circuit breaking capacity is : 1 kA 3) Type of MCB is : Type C For more detail,please contact the electrical engineer for their suggestion.This is a simple way to sizing the circuit breaker.Please refer the IEE manual for electrical guideline. PCWI Australia www.pcwi.com.au for Clamp Meters (Tong Testers) for Current and Voltage measurement Relays, Switches & Sensor www.comus.be Manufacturer Reed Relays & Switches Solid State Relays, Sensors LTspice IV www.linear.com/ltspice Free Circuit Simulation Tool & Schematic Capture Learn More! AC Power Sources www.elgar.com California Instruments, Elgar, AC Programmable Power /current Sources

Circuit breaker specific features for main switchboard Vacuum circuit breaker Molded case circuit breaker maintenance Types of motor overload relay Criteria for cable design Tags: abb, ampere, clipsal, mcb, mccb, safety, schneider, voltage

1.

Sinnadurai Sripadmanaban 24 April 2011 at 11:41 PM Permalink Please give an example for selection of MCB(type C or D)for a 3phase induction motor,say 10HP,15Amp- if started using an across the line(DOL) as well as wye-delta starter. Reply

2.

lemau 25 April 2011 at 1:34 PM Permalink from your example :10 hp;15 ampere

f9

8/3/2011 2 42 PM



the calculation is : 15 ampere x 0.25 = 3.75 + 15 ampere = 18.75 ampere So we can choose the MCB ampere rating = 20 ampere For induction motor with DOL stater,the suitable type is C or D Reply

Sinnadurai Sripadmanaban 3 May 2011 at 11:13 AM Permalink As the starting current is not the same for DOL and star-delta starters can we use smaller MCB for star-delta starting?. Is it correct if I say 20A for star-delta and 25A for DOL starting Reply

lemau 4 May 2011 at 9:42 AM Permalink U can use a smaller MCB but make sure it not below from the full load ampere rating.One more important thing is the TYPES of MCB must suitable with your application.Example MCB type C or D for motor stater.For more safety about overload protection,we still have the overload relay :D Reply 3.

Sinnadurai Sripadmanaban 5 June 2011 at 10:11 AM Permalink For frequent start/stop or DOL starting, OL relay won’t protect. MCB will trip for inrush current.So we used MCB type C rated 2xFLA for DOL and 1.5xFLA for star delta starting. Another important aspect is the rating and type of MCB should match the duty of motor -AC1,2,3 etc. For frequent start/stop like pressure switch operated water boosting pumps should be use type C duty AC3 or type D AC1?. Therefore the formula 1.25xFLA is for which duty class and will the tripping and contact wear problem will be solved for some class of duty by using class D MCB?. Please elaborate.Manufacturer’s literature will be a useful guide. Reply

4.

saouita 18 June 2011 at 9:18 AM Permalink stl Reply

Name (required) Mail (wil l not be published) (required)

5 f9

8/3/2011 2 42 PM



Website

Please tick to confirm you are NOT a spammer

Search This Site

High Voltage Power Cables, accessories & installation 66kV, 132kV & 400kV.XLPE, gas & oil www.elmeridgecableservices.c

Crane Overload Protection Cranegard, DynaSwitch, load limiting devices www.dqplus.com

高速同軸ケーブル高周波帯域に優れた特性を示す同軸ケーブル、その他各種ケーブル www.sanyu-tempflex.com

vacuum circuit breaker Air type Vacuum type www.Panickker.com/vcb.htm

Prevent Current Damage G&W Electric Co. Current Limiting Protector www.gwelec.com

Translation Tool

6 f9

8/3/2011 2 42 PM


Powered by


Translate

Latest post sent to your Email? Enter your email address:

Delivered by FeedBurner

Categories Automation Circuit Breaker Do It Your Self Earthing System Electric Motor Electrical Safety General Generator Hand Tools HVAC Lighting Measuring instruments Motor Control Theory wire & cable Wiring Techniques

Popular Posts Star delta starter Star delta motor connection Electrical Formulas Types Of Earthing Systems Direct on line starter Video Terminal connection for induction motor Conductor splices Search Results Induction motor fault finding Motor Overload Protection Miniature Circuit Breaker Sizing Miniature Circuit Breaker Electric motor testing

7 f9

8/3/2011 2 42 PM



Recent Posts Types of Molded Case Circuit Breaker MCCB MCCB protection for induction motor What is electric shock? How to servicing the magnetic contactor? Electrical installation How to select the best location for install split unit air-conditioner? How calculate ampere for electric motor? How to choose speed controllers for AC motor? Vacuum circuit breaker How to install lug for electric cable?

Archives August 2011 (1) July 2011 (17) June 2011 (19) May 2011 (25) April 2011 (11) March 2011 (20) February 2011 (21) January 2011 (11) December 2010 (2) October 2010 (15) September 2010 (26) August 2010 (4)

Related Pages Hand Tools Review Electrotechnik HVAC Tutorial solar pv systems

General Info Technology blogs

Home Automation Circuit Breaker Do It Your Self Earthing System Electric Motor Electrical Safety

8 f9

8/3/2011 2 42 PM



General Generator Hand Tools HVAC Lighting Measuring instruments Motor Control Theory wire & cable Wiring Techniques © Electrical Engineering Centre. (2010 - 2011) email : [email protected] This page took 3.0 seconds to load.

9 f9

8/3/2011 2 42 PM

Miniature Circuit Breaker Sizing _ Electrical Engineering Centre

Recommend Documents