Characteristics Of Mcb 2l3a32

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Characteristics of MCB Thread Starter: Import--1 Started: 10/24/2011 1:13 PM Replies: 3 « Previous thread Next thread » Page 1 of 1 (4 items) 10/24/2011, 1:13 PM Import--1

(0) Saran Kumar wrote: Dear Friends, I need the answers for the following questions,

ed 8/10/2005 Last visit: 4/9/2014 Posts: 3287 Rating: (18)

1. What are characteristics of MCB & Where it will applicable? 2. Difference b/w above characteristics? (i.e, Diff b/w B-Curve, C-Curve, K,L,M - Curve) Kindly Solve this issue. Regards, Saran Top

10/25/2011, 5:50 AM (0) Import--1 wrote: Saran Kumar wrote: Dear Friends, I need the answers for the following questions, Ayman Elotaify

1. What are characteristics of MCB & Where it will applicable? 2. Difference b/w above characteristics? (i.e, Diff b/w B-Curve, C-Curve, K,L,M - Curve) Kindly Solve this issue.

ed 5/28/2008 Last visit: 4/10/2014 Posts: 2774 Rating: (532)

Regards, Saran Hello Saran, Based on the Tripping Characteristics, MCBs are available in ‘B’, ‘C’, ‘D’, 'Z', 'K' and 'S' curve to suit different types of applications. ‘B’ Curve: for protection of electrical circuits with equipment that does not cause surge current (lighting and distribution circuits). Short circuit release is set to (3-5) In ‘C’ Curve: for protection of electrical circuits with equipment that causes surge current (inductive loads and motor circuits). Short circuit release is set to (5 - 10) In ‘D’ Curve: for protection of electrical circuits which causes high inrush current, typically 12-15 times the thermal rated current (transformers, X-ray machines etc.). Short circuit release is set to (10 - 20) In ‘K’ Curve: Suitable for applications where high levels of inrush current are expected. Instantaneous trip is (8 - 12) In. The high magnetic trip point is ideal for motors and transformers. The narrow range (compared with the type D curve) makes it ideal for applications where nuisance tripping is not an issue. ‘Z’ Curve: Suitable for applications where semiconductors and other components that fail open are

used. Instantaneous trip is (2 - 3) In. The short thermal delay and low magnetic trip point are ideal for applications where devices and components have low surge and short circuit tolerances. ‘S’ Curve: Suitable for applications with highly inductive loads, especially in control circuits with coils and light filaments. Instantaneous response between (13 - 17) In. Note: 

If you use the B MCB in place of D curve MCB, chances are the B curve MCB s can weld together, or there will be nuisance trippings. On the other hand, if you use a D curve where a B curve MCB has to be used, the system will damage before the breaker can trip.

Hope this helps.

=== Edited by Ayman Elotaify @ 10/25/2011 5:52 AM [GMT ] ===

Ayman Elotaify MISC Egypt www.miscegypt.com Top Thank you for this post from: AMAZINGAHMED, DILIP_1111, Arun Kumar Yadav 10/27/2011, 11:18 AM Saran Kumar (0) Dear Ayman, Thank you!.... ed 10/24/2011 Last visit: 7/9/2012 Posts: 2 Rating:

Regards, Saran Saran.

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Between what two quantity A/B/C OR D-Curves makes in MCB? I just want to technical difference between A,b,c, and d curves of Mcb. with proper explanation.And why we do so.????

Best Answer 

Subramaniam answered 3 years ago

A breaker is to protect the system from damage due to high currents or short circuits. There are B,C and D curve MCBs. Each differ in capability to interrupt the load current safely in certain time. B curve MCB trip from 3-5 times of rated current safely meant for smaller inrush current loads. C curve MCB trip from 5-10 times of rated current safely meant for medium inrush current loads.. D curve MCB trip 10-15 times rated current safely meant for heavy inrush loads like motors. If you use the B MCB in place of D curve MCB, chances are the B curve MCB s can weld together, or there will be nuisance trippings. On the other hand, if you use a D curve where a B curve MCB has to be used, the system will damage before the breaker can trip

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Answers (1) 1. Many different classifications of circuit breakers can be made, based on their features such as voltage class, construction type, interrupting type, and structural features. Low voltage circuit breakers

Low voltage (less than 1000 VAC) types are common in domestic, commercial and industrial application, include:

MCB (Miniature Circuit Breaker)rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category.

MCCB (Molded Case Circuit Breaker)rated current up to 1000 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings. RCB __ RCCB : -- RESIDUAL CURRENT CIRCUIT BREAKER//CIRCUIT BREAKER//BREAKER This product provide a high level of protection aganist earth leakage faults by the RCD in addition to the over and short- circuit protection offered by the MCB. Rated voltage 400v and below. Rated current 6A 10A 16A 20A 25A 32A 40A 50A 60A. It conforms to GB16917-97 It' s pole is 1P, 2P, 3P, 4P. It is 1P.

ELCB :- An Earth Leakage Circuit Breaker (ELCB) is a safety device used in electrical installations with high earth impedance to prevent shock. ...less Answered by anantharaman, 01 Mar '10 11:33 am

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What is the difference between mpcb and mccb?

where should we use mccb and where should we use mpcb. constructural difference

Best Answer 

desai b answered 4 years ago

1. MPCB is ment for motor protection only where as MCCB is for various application including Motor. 2. In MPCB we do not talk about Ics / Icu no cat. configuration - class A / class B type of breakers. For TYpe -2 Coordination we need to have external devices like -- or, o/l relay, or etc. with MCCB while with MPCB we have inbuilt configuration of Type -2 coordination (no external device) 3. MPCB has an inbuilt or and relay.so need for external contaectors and relays. MCCB ther is no or and relays, we have to provide. 4. MCCB - Moulded case Circuit breaker, is having overload and s.c. protection & used in Industrial application & Having

high s.c. capacity MPCB : Motor protection circuit breaker, is used for protection of motor, having s.c. and overload protection more effective to protect motor 5.MPCB has got thermal element....with more narrow range, settable to set with reference to motor full load current.

3

MCCB SELECTION FOR TRANSFORMER PROTECTION

Thread Starter: jayanta Started: 7/18/2010 10:03 PM Replies: 10 « Previous thread Next thread » 12›» Page 1 of 2 (11 items) 7/18/2010, 10:03 PM (0) Dear Experts, jayanta

can tell me if MCCB (cat no. - 3VT1708-26A36-0AAa0) is suitable for protection of transformer? If yes, can explane me selection prosidute. Because the above mention MCCB (80A) is tripping in inrush current of a 37kva (415/240V) transformer. Kindly give us reply.

ed 7/18/2010 Last visit: 8/28/2010 Posts: 4 Rating: (0)

Thanks in advance.....

=== Edited by jayanta @ 7/18/2010 10:04 PM [GMT ] ===

Top 7/19/2010, 8:20 AM PISCEAN 2010

(0) Transformer primary is 2~ or 3~?. How & what type of load is connected to sencondary?. Thru or, relay or directly. How much is seondary fuse or MCCB rating? DEEP. ed 4/23/2010 Last visit: 4/9/2014 Posts: 1540 Rating:

Tell me and I will forget. Show me and I will . Involve me and I will understand. -Confucius

(72) Top 7/19/2010, 5:02 PM

jayanta

(0) Transformer's primary & sencondary is 3~. Sencondary open. But actually it will be connected with thyristor circuit. ed 7/18/2010 Last visit: 8/28/2010 Posts: 4 Rating:

Jayanta

(0) Top 7/20/2010, 6:33 AM PISCEAN 2010 (0) Hello Jayanta, The specified MCCB is of general purpose MCCB & not of dedicated MCCB for only LV transformer protection. The 80 Amp range selection is correct one but the breaking capacity 25 KA is not adequate for industrial or your application. Just try MCCB of amp >70 A rating with 50 KA breaking capacity. Regards, DEEP. ed 4/23/2010 Last visit: 4/9/2014 Posts: 1540 Rating:

Tell me and I will forget. Show me and I will . Involve me and I will understand. -Confucius

(72) Top 7/20/2010, 7:42 PM jayanta

(0) Mr. Deep, ed 7/18/2010 Last visit: 8/28/2010 Posts: 4 Rating:

We also tested this Transformer by useing 63A, 25KA, Cat No. - 3VT1706-2DC36-0AA0 MCCB and no any problem arrive.

(0) Top 7/21/2010, 7:41 AM PISCEAN 2010

ed 4/23/2010

(0) Mr. Jayanta, With 63 A, 25 KA MCCB, have you checked the transformer on load or only transformer is checked? Moreover, if on load you have not faced any problem with 63A 25 KA rating MCCB & on same transformer, 80A 25 KA MCCB is tripping, then in that case your 80A, 25 KA rating MCCB may be faulty. Please check. DEEP. Tell me and I will forget. Show me and I will . Involve me and I will understand. -Confucius

Last visit: 4/9/2014 Posts: 1540 Rating: (72) Top 7/21/2010, 7:41 AM PISCEAN 2010 (0) Mr. Jayanta, With 63 A, 25 KA MCCB, have you checked the transformer on load or only transformer is checked? Moreover, if on load you have not faced any problem with 63A 25 KA rating MCCB & on same transformer, 80A 25 KA MCCB is tripping, then in that case your 80A, 25 KA rating MCCB must be faulty. Please check. DEEP. ed 4/23/2010 Last visit: 4/9/2014 Posts: 1540 Rating:

Tell me and I will forget. Show me and I will . Involve me and I will understand. -Confucius

(72) Top 8/27/2010, 8:03 PM (0)

Dear All / Mr. Deep I like to inform you that the said 63A MCCB is Siemens make Characteristic „D“, & 80A MCCB is Characteristic „L“. I think (after watching MCCB catalogue) these two types of Characteristic MCCB is totally different. I also like to inform you that we tested the said transformer using lots 80A (same type) MCCB. So, please inform/guide me I/C MCCB selection calculation to avoid MCCB tripping at switching inrush. it would be better if anyone can give me ing document also.

jayanta

ed 7/18/2010 Last visit: 8/28/2010 Posts: 4 Rating: (0)

For any information anyone can also mail me ([email protected]). Please guide me with ing document. Jayanta

=== Edited by jayanta @ 8/28/2010 5:20 PM [GMT ] ===

Top 2/11/2011, 4:24 PM

(0)

Sentronix

ed 2/4/2010 Last visit: 3/19/2014 Posts: 46 Rating: (4)

Hello Jayanta, As I understand problem is line-side protection of a transformer? We have to see that an inrush current of 20...30 x In (rated current) is realistic. Instantaneous trip (Ii) of a MCCB is about 10...13 x In. Therefore the circuitbreaker must be operated in its lower setting range. Example: Inrush current for a transformer In = 500A may be higher than 10000 A. Selection: Breaker In = 1000A, setting of In = 500 A, Ii = 11 x In = 11000 A (22 x setting of In). It must not be forgotten that the circuit breaker has to trip on the minimum shortcircuit Ikmin. So the breaker should provide short time delayed shortcircuit protection (Isd), which normally can be set to 2...10 x In and a time delay of a few hundred milliseconds. Please be aware not to use a breaker for motor protection. Phasefailure sensitivity may lead to unintentional tripping behaviour. Regards, Sentronix Top

5/9/2011, 6:49 PM (0)

Hello Colleagues

VonSiemens

ed 9/28/2010 Last visit: 1/31/2012 Posts: 6 Rating: (0)

1.

When switching on low-voltage AC transformers, the extremely high inrush current peaks place special demands on the trip unit or on the making capacity of the circuit breakers if these are also used to switch the transformer.For most applications, an inrush current of 20 to 30 times the rated operating current is expected in practice and must be taken into when selecting the circuit breakers. The maximum short-circuit current Ik of the 3VL circuit breakers is 11 x Ie (rated operating current). A circuit breaker in the lower setting range must therefore be operated for primary side transformer protection. Example: A transformer with 500 A rated current; 20 times the inrush currentSelected: ETU with In = 1000 A; setting range 0.4 - 1 x In = 400 A to 1000 A50% of In = 500 A; Ii = 11 x In = 1000 A x 11 = 11000 A = 22 x current setting

minerman

Junior Member Date Aug 2011 Location Columbus, Ohio, United States Posts 23 4

MCCB Instantaneous Trip Setting

Does anybody know how to determine an MCCB instantaneous trip setting? I haven't done this in a couple years. I was thinking 10 or 15x the FLA? Thanks.

2.

12-08-11, 12:46 PM #2

kingpb Senior Member Date Jul 2006 Location SE USA as far as you can go Posts 2,171 In general, it must be set to trip below the minimum fault current that it will see, assuming the maximum capability of the equipment is greater than the minimum fault current. "Just because you're paranoid, doesn't mean they're not out to get you"

3.

12-09-11, 09:58 AM #3

Jraef Senior Member Date Jul 2006 Location

San Francisco, CA, USA Posts 3,336 Read Article 430, specifically table 430.52, and read the exceptions as well, and make sure you understand all of them. If you have more uestions after that, post them here again. __________________________________________________ ____________________________ "Dear future generations: Please accept our apologies. We were rolling drunk on petroleum." — Kilgore Trout (via Kurt Vonnegut)

4.

12-09-11, 10:28 AM #4

raider1 Date Jun 2005 Location North Logan, Utah Posts 7,919 I think the poster is asking about a molded case circuit breaker. If that is the case to determine the instantaneous trip threshold you need to get the circuit breakers trip curve data from the breaker manufacture. Chris

5.

12-09-11, 12:02 PM #5

zog Senior Member Date Feb 2005 Location Charlotte, NC Posts 6,291 Originally Posted by minerman

Does anybody know how to determine an MCCB instantaneous trip setting? I haven't done this in a couple years. I was thinking 10 or 15x the FLA? Thanks.

Are you asking how to determine WHERE it should be set or how to determine WHAT it is set at?

6.

12-09-11, 01:20 PM #6

ATSman Senior Member Date Aug 2008 Location Bay Area, CA Posts 316 Originally Posted by minerman

Does anybody know how to determine an MCCB instantaneous trip setting? I haven't done this in a couple years. I was thinking 10 or 15x the FLA?

Thanks.

To be compatible with the coordination study, it should be set at just above the inrush current of the largest connected load on startup. If the breaker is in an MCC then I would follow the old Westinghouse recommended procedure: 1. Raise the inst dial to max. 2. Start and stop the motor. 3. Lower the setting 1 notch each time you restart motor until the breaker trips, then raise the dial 1 notch. 4. Restart motor to prove no-trip. This will be the final setting. This setting should match the trip curves in the study and also takes into cable impedance, as well. Am I in shape?? I get plenty of exercise pushing my luck!!

7.

12-09-11, 02:27 PM #7

jim dungar Date Feb 2003 Location Wisconsin Posts 8,569 Originally Posted by tonytonon

To be compatible with the coordination study, it should be set at just above the inrush current of the largest connected load on startup. If the breaker is in an MCC then I would follow the old Westinghouse recommended procedure: 1. Raise the inst dial to max. 2. Start and stop the motor. 3. Lower the setting 1 notch each time you restart motor until the breaker trips, then raise the dial 1 notch. 4. Restart motor to prove no-trip. This will be the final setting. This setting should match the trip curves in the study and also takes into cable impedance, as well.

When doing this type of "click and hope" adjustments, make sure you are not exceeding both the # of starts/hr and the time between starts of the driven equipment. Just because you can, doesn't mean you should.