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MCB tYPES

10/07/2009 9:05 AM

What are the Diff. Types of MCB' (like B,C etc) and on what basis they are Differenciated

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#1

Re: MCB tYPES

10/07/2009 9:26 AM

Well, both switchgear/breakers and also dynamo drivers use the terms MCA, MCB, MCC, and MCD...which are you asking about, breakers or drivers ?

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#2

Re: MCB tYPES

10/07/2009 9:32 AM

It's all to do with their disconnect time characteristic. A type B breaker will disconnect slightly faster for an overload than a type C, and so-on. One might find B breakers on resistive loads, and C type on those loads that are small motors, for example, so as to give the motor an opportunity to spin-up while its starting current is marginally more than the breaker can sustain in the long term.

British Standard 7671, surprise surprise once again, covers this subject in full detail, and copies of this standard may be ordered on-line from BSI Publications.

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#3

Re: MCB tYPES

10/07/2009 10:47 AM

There are three types of MCBs. They are Type 'B', Type 'C' & Type 'D'. As you are aware an MCB provides both overload (thermal) and short circuit (magnetic)protection. As for the overload protection is concerned, there is no difference in the charecteristics of these three types of MCBs. But, the difference is in their short circuit protection response.

Type 'B' short circuit operating range is 3 to 5 In (In is the Nominal Current Rating of the MCB)

Type 'C' short circuit operating range is 5 to 10 In and

Type 'D' short circuit operating range is 10 to 20 In.

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