What happens when you disconnect a neutral at source in a three phase system?

Answer 1

== == == == It is true. Damage will most likely result somewhere, maybe not everything. When a neutral on a multi-wire circuit is opened (open-circuited) (removed) (cut) while things are under load, the voltage will change at the loads. Some loads will get more than normal, some will get less. The damage usually occurs on the side that gets MORE voltage. For example: your TV may be on a circuit that goes from 120volts to 50 volts, while your light bulb goes from 120volts to 180volts and blows. It all depends on how "balanced" the circuit is. In theory, if the loads are perfectly balanced then the neutral is not needed. In reality loads vary constantly, therefore, the voltage will vary if the neutral is open-circuited. That means running with an open neutral is something that anyone with any smarts at all will not do. It is absolutely possible to damage equipment by opening the neutral in some circumstances. <><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

If you do this work yourself, always turn off the power

at the breaker box/fuse panel BEFORE you attempt to do any work AND

always use an electrician's test meter having metal-tipped probes

(not a simple proximity voltage indicator)

to insure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer 2

You will open or break the circuit to any single phase circuits being supplied by the panel.

Three phase panels which are supplied with a neutral typically supply a variety of circuits, power, lighting and motor circuits such as air conditioning. A 3 phase motor circuit will have three pole circuit breakers, one breaker occupying three spaces in the panel and buss bar. The single pole circuit breakers are supplying single phase power via the single "hot" phase off the breaker and the neutral Also, many three phase circuits may employ the neutral for low voltage control.

In a low voltage (208-240V) three phase panel, the three pole breakers are supplying 208-240 volt power. The single pole breakers are supplying 110 volt. (with the neutral as the "return" to complete the circuit.)

In a high voltage (480V) three phase panel, the three pole breakers are supplying 480 volt power and the single pole breakers are supplying 277 volts with the neutral as the return. 277 volt power is used almost exclusively for commercial lighting loads.

The bottom line here is you don't want to disconnect the neutral from any panel. It's there for a good reason!

Another AnswerFor an unbalanced load, the removal of the source's neutral connection will result in unbalanced phase voltages