3 pole MCCB vs 4 pole MCCB
3 pole MCCB vs 4 pole MCCB
(OP)
Hi All,
Can someone explain to me the advantages of 4 pole MCCB over 3 pole MCCB ?
Regards,
Darren
Can someone explain to me the advantages of 4 pole MCCB over 3 pole MCCB ?
Regards,
Darren






RE: 3 pole MCCB vs 4 pole MCCB
If you have a need to disconnect the neutral at the same time as any of the phases in a 3 phase AC system you'd use a 4 pole breaker. If not, you'd use a 3 pole.
For an LV DC system, depending on voltage, you might need 4 poles in order to successfully break the DC arc.
EDMS Australia
RE: 3 pole MCCB vs 4 pole MCCB
RE: 3 pole MCCB vs 4 pole MCCB
RE: 3 pole MCCB vs 4 pole MCCB
For other locations may be discretionary based on the cost v/s benefit analysis.
RE: 3 pole MCCB vs 4 pole MCCB
RE: 3 pole MCCB vs 4 pole MCCB
Some sectionalizing and transfer arrangements may need a four pole breaker in order to properly monitor ground fault currents.
This is particularly true for impedance grounded systems but may apply to some solidly grounded systems also.
In the NEMA world the standard, unless special conditions apply, is a three pole breaker.
This also applies to a large portion of the oil and gas industry.
Some designers strive to arrange the grounding so that a four pole transfer arrangement is NOT needed.
A four pole transfer arrangement adds at least two more possible points of failure.
Bill
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"Why not the best?"
Jimmy Carter
RE: 3 pole MCCB vs 4 pole MCCB
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
RE: 3 pole MCCB vs 4 pole MCCB
Bingo!
In North America, it should never be needed. 4 wire systems must be solidly grounded here. Resistance grounded or floating systems MUST be 3 wire and only contain line to line connected loads. Dedicated transformers must be used for 277V (or 343V) loads.
Under IEC wiring rules, TT and IT systems can and usually do have line to neutral loads. In this case, the neutral must be switched to protect against the neutral shock hazard and to protect against double fault conditions. (Imagine a scenario light fixture with a neutral - earth short and then a big motor grounds out. If that lamp circuit doesn't contain a neutral breaker, the neutral will burn.)
RE: 3 pole MCCB vs 4 pole MCCB