why is 400 volts used when calculating PSCC for a 3 phase mains cable? i.e 230/Ze or 400/Ze?

Question

i want to know the reason 400 volts is used, not 230 volts in 3 phase, i know its a 400 volt canle but 230 volts would surley be a better worse case figure to use...

Answer 1

Because the voltage between two phases = phase voltage (230 V) * 2 * cos 30° = 398 V.

For explanation google alternating current.
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Answer 2

there are several types of three phase.

1 hot wire110 volts between neutral or ground
between any 2 hot wires 208 volts.

the delta or Wye system 120 volts 0n 2 hot wires to ground but a high leg with 200 volts.usually for large motors and machines.

There is 277/480 which places such as walmart buy from the power company.again it used for lighting and large machines.The store will then have a transformer to reduce down to the 110/208 volt

Answer 3

draw a line up the vector from any peak this will give you the answer, showing the ratio of the other two phases