3 Phase Generator

[wwhitney]

You have a 240 delta machine that is 10 kW / 12.5 kVA.

That is 30 amps per corner on 3 phase loads. Because each corner is being supported by both sets of windings. The individual windings carry less than the full 30 amps.

Yes, my mistake. 30A is the line current. The coil current would be 30A / sqrt(3) = 17.3A.

If you take single phase load from 2 corners, the max is still 30 amps due to total heat dissipation in the windings.

The in-phase winding will be carrying 20 amps, and the out-of-phase windings will be carrying 10 amps.

OK, but 20A is greater that the 17.3A maximum coil current from a balanced 12.5 kVA 3 phase load. So wouldn't the maximum single phase current be 17.3A * 1.5 = 26A?

Cheers, Wayne

 

[Birken Vogt]

OK, but 20A is greater that the 17.3A maximum coil current from a balanced 12.5 kVA 3 phase load. So wouldn't the maximum single phase current be 17.3A * 1.5 = 26A?

I know the in-phase coil is going to run above its own theoretical individual rating.

But that is the way they have always rated single phase delta configurations since the dawn of time. The out-of-phase coils will be far below their individual rating at the same time.

If you do the math, you will find that total heat dissipation throughout the stator is less, as a single phase delta, than its functional equivalent, the dogleg.

But I have never been inside the engineering and testing department to know how they come up with these ratings.