3 wire or 4 wire?

[JSelf]

Could anybody tell me in 3-phase power when I would use a "3ph/4w/Ground" setup rather than a "3ph/3w/Ground" setup. I am a bit confused as to which I use in a given situation. Thank you,
Jason Self

 

[rbulsara]

If your loads require a neutral, meaning if some load is connected between line and neutral then you need 3 phase, 4W and GND. If all the loads are three wire such as 3 phase transfomers or 3 phase motors only, you can get away with only 3 ph, 3W and GND.

If the single phase loads is a very small part of the larger 3 phase loads, you may wish to use a small 3ph, 3w to 3ph 4W transfomer to feed single phase loads and keep the majority of the system 3 phase, 3W.

 

[jbartos]

Comment: 3ph/3w/ground is used for dedicated loads that do not need neutrals, e.g. motors, heaters, converters, etc.
3ph/4w/ground is used for general or mixed loads. Also, the system grounding methods should be noticed since 3ph/3w/ground can be ungrounded.

 

[Mahase30]

The response above is short but very direct. Only use 3p/4w when the load is mixed

 

[JSelf]

Thanks everyone that clears things up a bit.