Motor MCCB

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Let me re-phrase my problem:To avoid confusion, let's take a large motor for which we can only use MCCB (not MCB). let's say 110 kW DOL motor. The Schneider's recommended combination is: magnetic only breaker (NSX250HMA220) plus contactor (LC1F225) plus overload (LRD05.)

The motor FLC is 200A, and let's assume the starting current is 1000A.

Now here is my problem:

How can I set the magnetic trip to 1000A, while the maximum breaker frame size is 250A?
the frame size does not relate to instantaneous trip currents.

the frame size is just the physical mccb size not its operational characteristics

 
yes side. he doesn't need one either

a 63A type d mcb will hold 1000a for 3secs

500A for 8 secs

 
Loyal comes from America is this going to make a difference to what circuit breaker is needed?
hmmm they have 110 for single phase 3 phase no idea

potential much more current with the lower voltage

well spotted

 
Loyal comes from America is this going to make a difference to what circuit breaker is needed?
Missed that!!! Wet Fish

No in the words of an imortal "engineer", "ye cannae deny the laws of physics Captain".

I'm not too familiar with the NEC, but, the required power will not really change.

BTW Y/D is more their term than ours! It is just easier to type!

 
S&S,

Sou've confused me a little with this, not difficult especially at this time of night!

Zs has not come into it!

We were talking about TM O/L settings in the starter.

Also, for large motor supplies they may come from bus bar systems, & the OP was talking about MCCB's.

These require a MUCH lower Zs than even a D curve 60898.

Sorry buddy, not sure where you wre going with that?

:)

 
S&S,Sou've confused me a little with this, not difficult especially at this time of night!

Zs has not come into it!

We were talking about TM O/L settings in the starter.

Also, for large motor supplies they may come from bus bar systems, & the OP was talking about MCCB's.

These require a MUCH lower Zs than even a D curve 60898.

Sorry buddy, not sure where you wre going with that?

:)
It is a bit late, i was referring to an earlier post that mentioned fitting a 50A breaker. You mentioned Zs has not come into it, but it should, baring in mind this sounds like a industrial job where the motor may be a fair distance away from the distribution.

 
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