3 pole or 4 pole breakers
3 pole or 4 pole breakers
(OP)
I am working on 400V system. 4 wire system is required for the incoming section. so the 4 pole circuit breaker is needed for the main incomers.
IEC also recommends that 4 pole circuit breakers shpould be used if SWGR or MCC feeds equipment in a hazardous area. But I am not sure about the theory behind it. Is it really necessary to do so? I noticed that a lot of people just simply 3 pole circuit breakers.
IEC also recommends that 4 pole circuit breakers shpould be used if SWGR or MCC feeds equipment in a hazardous area. But I am not sure about the theory behind it. Is it really necessary to do so? I noticed that a lot of people just simply 3 pole circuit breakers.






RE: 3 pole or 4 pole breakers
Except for a few fairly rare exceptions, the neutral is rarely switched in NEMA land. If the neutral is switched, the codes require the neutral to be either simultaneous operating or early make late break.
In the event of the failure of one pole of the switch or breaker to close, loss of one line of a three phase supply rarely causes damage, but an open neutral connection often causes expensive equipment damage.
My rule of thumb is to avoid neutral switching if it is at all possible.
respectfully
RE: 3 pole or 4 pole breakers
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: 3 pole or 4 pole breakers
Why? The neutral is normally left solid, unless a source transfer arrangement is present. If the neutral is switched then the breaker must be a 4-pole device, but normally a 3-pole device with a solid neutral is adequate.
The main reason I can see for a switched neutral in a hazardous area would be to prevent a possible ignition source if the neutral conductor made contact with earthed metalwork. I don't believe switching the neutral on a standard TNS or TNC-S distribution service is a requirement in the UK, or by implication in Europe because ATEX is a standard for the whole EU. There may be a requirement if you are using some unusual earthing system, e.g. an IT source or a high resistance grounded source where a significant voltage between neutral and earth could exist. Both of these are almost unheard of in the UK for LV systems, so I can't offer much guidance.
----------------------------------
Sometimes I only open my mouth to swap feet...
RE: 3 pole or 4 pole breakers
RE: 3 pole or 4 pole breakers
RE: 3 pole or 4 pole breakers
RE: 3 pole or 4 pole breakers
Rugged
RE: 3 pole or 4 pole breakers
RE: 3 pole or 4 pole breakers
RE: 3 pole or 4 pole breakers
Could you cut & paste the section of IEC 60364-1 which prohibits use of a solid neutral? I don't have the standard but I'm interested to have a read of that part because it is significantly different to the requirements of BS7671. The British wiring regs are different to the European equivalents: that's why the British Standard doesn't bear an EN number and won't until conformance with (assimilation into?) Europe has occured.
----------------------------------
Sometimes I only open my mouth to swap feet...