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6 comments
Active Contributor

Join Date: Aug 2008
Posts: 14

Difference between ACB and MCCB

09/22/2008 7:31 AM

Hi,

Can any body explain the difference between Air circuit breaker and Moulded case circuit breaker.Can We use 800 A MCCB in place of 800 A ACB.What will be the difference in protection features.

Prasad.K

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Guru
Safety - ESD - New Member India - Member - New Member Engineering Fields - Energy Engineering - New Member

Join Date: May 2007
Location: Pune , India
Posts: 824
Good Answers: 39
#1

Re: Difference between ACB and MCCB

09/22/2008 10:08 AM

Hi klsvp72,

Please read all the discussion on the same question on 08/14/2008. I quote my answer for the same below :-

"

ACB and MCCB both are used for safe making and breaking of electrical system. In principle both serve the same purpose. Earlier concept was to use OCB/ACB / when large load currents were to be handled because they were very robust and could withstand high making and breaking capacity and allow many frequent safe making and breaking .Due to various fire hazards and high coast of maintenance,the use of OCB in LT distribution is getting eliminated .

With technological development a new version of circuit breakers were introduced with moulded case which were initially having only very low load break capacity.They were much cheaper and use and throw type and could be used for only limited number of operations.

With further development in technology, the at present day MCCB are designed with larger make and break capacity and fault withstand capacity. As stated by Baby Guinness now MCCB with capacity of 3200 A and breaking capacity of 200KA with all control benefits and dependable quality are available from reputed manufacturers. They need less space in the panel compared to ACB.

ACB has robust enclosure, draw out facility, sliding shutters and capacity to withstand many break and break operation with out damage and proven technology. ACB is still preferred for on load switching operation of 800 Amps and higher systems."

It is always better to read previous threads before putting up a new thread to avoid repetition
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Active Contributor

Join Date: Aug 2008
Posts: 14
#2
In reply to #1

Re: Difference between ACB and MCCB

09/23/2008 12:16 AM

Hi V.I.Abraham

Thanks for the Ansawer.

Prasad.K

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3
Active Contributor

Join Date: Jun 2008
Posts: 17
Good Answers: 1
#3

Re: Difference between ACB and MCCB

09/23/2008 1:39 AM

For short circuit protection, it is importent to break the circuit quickly - before the current reaches to its prospective peak value, to limit the let through energy & corresponding damage it can casue.

In good olden days (before advent of MCCB), this function was being done effectively by fuses on load side.

But this was expesive as every time, you need to replace the fuse.

ACB mechanism is very heavy - with high inertia, & hence can not break the circuit as fast as fuses.

The concept of MCCB was developed to give short circuit protection on load side, by making its mechanism as light as possible - to enable it to beak the circuit very fast - & hence MCCB could replace fuses for giving short circuit protection with least operating cost!!

ACBs are usually seen on upstream side of circuit & MCCBs on load side control. (Usually, load side switching operations are more frequent than upstream)

As the technology has improved over the period of time, the rating & breaking capacities of MCCBs are increasing - hence there is possibility of overlap in application of ACB & MCCB.

As far as replacement of ACB with MCCB is concerned, it is possible - but please take care of proper co ordination with other down stream & upstream switchgear!!

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Active Contributor

Join Date: Sep 2008
Posts: 16
#4

Re: Difference between ACB and MCCB

09/28/2008 12:58 PM

dear sir,

mccb comes in 'A' category according to the IEC and ACB comes in 'B' category .

b category means that the breaker which has a ( ICW ) short circuit with stand capacity and a category is vice a versa .

which means where we dont want any instantanious tripping , we can use ACb there because it has a tendency to withstand the fault for a certain period and thus in the meanwhile we gets the time to switch the secondary supply and thus continuous functioning of the production .

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Member

Join Date: Oct 2008
Location: India
Posts: 7
#5

Re: Difference between ACB and MCCB

10/30/2008 6:40 AM

ACB & MCCB are different as many aspect. 1.The no of operations in fault & in on load conditions are less for MCCB. 2.MCCBs are not of rigid structure,generally of plastic body but ACB has a steel enclosure. 3.MCCBs break the circuit at 1st or 2nd cycle of fault current.ACB can withstand a huge amount of fault current. Moreover it depends on the application Thanking you Prithwiraj Ghatak

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Anonymous Poster
#6
In reply to #5

Re: Difference between ACB and MCCB

09/21/2010 2:16 AM

Major difference between MCCB and ACB is that ACBs are category B devices where as MCCBs are category A Devices. This means that MCCBs do not haev Icw rating and are not suitable for full discrimination. discrimination up to certain falut level can only be achieved with MCCBs.

Regards

Vinod M Panchal

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