3 phase converter figures.

[aussiejoeblow]

Hi all,

Just been poking around my 3 phase converter and was wondering if anyone could help me with the figures I have.

Step up transformer (240-415volt) running into a 4kw 3ph motor.

L3 is the generated leg.

L1 to L2 is 413 volts.
L2 to L3 is 403 volts. (24uf run capacitors)
L1 to L3 is 468 volts. (48uf run capacitors)

L1 to earth is 416 volts.
L2 to earth is 0 volts.
L3 to earth is 404 volts.

L1 to 240in is 175 volts.
L2 to 240in is 238 volts.
L3 to 240in is 392 volts.

I was under the impression that legs to earth should be around 240 volt mark. Am I missing something?

Joe.

[Vernonv]

I was under the impression that legs to earth should be around 240 volt mark. Am I missing something?I'd say the step-up transformer is the reason for those numbers i.e. before transformer 240V A to E, after transformer 415V A to E.

[.RC.]

I am wondering why the readings between a phase and neutral differ from a phase and earth, since the earth and neutral are wired together at the switchboard..

[Vernonv]

I am wondering why the readings between a phase and neutral differ from a phase and earth, since the earth and neutral are wired together at the switchboard..I'm guessing that the transformer is an isolation transformer. The E and N are only bonded on the primary side of the transformer.

[aussiejoeblow]

Sorry RC, those readings were taken from the input 240 to the transformer. Now edited.

What has me curious is L2 to earth.

[.RC.]

Mine must have an auto transformer then...

[malb]

Please sketch out what you are doing, paying particular attention to the transformer winding configuration, Neutral and Earth and the connections to the motor. I think I understand what is happening, but there are two many permutations to discuss each possibility without confusion.