Power Generation - Wye and Delta

AFAIK..

on 3-PH, you'll have a certain voltage across each individual winding, say 208V (AC)

in Delta Configuration, you'll have 208V on each phase

in Wye Configuration, you'll have the 208 from phase -> Neutral, but 480 from phase to phase..

I guess you know that part, but I think its the current's available on the phases that makes most of the differance.

Going the other way, we had some 3-PH motors here at work, they were wired up as Wye, but were powered from 1-PH -> 3-PH power converters, the output from the motors wasn't enough and kept stalling, it was later found that the motors needed to be configured for the other connection.

So, 240VAC in, and then converted to 3-PH (don't think I need the calcs for the resulting lower voltage)

Instead of having the voltage applied across each winding, it was divided across each winding as such

Ph1 - Ph2 = W1+W2

Ph2 - Ph3 = W2+W3

Ph3 - Ph1 = W3+W1

In Delta it would have been ..

Ph1 - Ph2 = W1

Ph2 - Ph3 = W2

Ph3 - Ph1 = W3

May have drifted OT, but I feel its still relevant ;o)

Your numbers are off, but the basic premise is correct. The relationship of phase-neuitral voltage to phase-phase voltage on a wye connection is √3, or about 1.732. If phase-neutral is 208V, phase-phase will be 360V. For 480V phase-phase out, the phase-neutral will be 277V.

I suppose it's possible to make a 12-wire genset produce 208 and 480 in Wye, but you'd have to do some serious adjustment on the voltage regulator. Producing 208V requires 120V from each of the 12 winding coils (connected parallel star). For 480V, you'd need 138.5V out of the same coils (connected series star), a 15% increase. Most regulators are only good for +/- 10%, and the winding insulation may not be good for the higher voltage.

For 12 wire generator, we have 6 coils.

If the series star produce 480 volt and 1000A (say), then each coil produce half of (480/√3),

(480/√3)≈280

Then V_coil=0.5x280=140v.

Now;

Series star: V=480volt , I=1000amp

Parallel star: V=240volt , I=2000amp

Series delta: V=480/√3=280volt , I=1000x√3=1732amp

Parallel delta: V=240/√3≈140volt , I=2000x√3=3464amp

these are the available combinations, and you can see the differences.

Note that the power is constant in all of the above.

Samak