2000 KW GEN SET 440V Not Developing Voltage

I don't know, but I bet the generator manufacturer does. I'd get on the phone and at least talk the problem through with them and possibly get someone in.

I agree with Crabtree. I think the problem is located in excitation circuit. If the exciter is a dc generator then check the armature current and the exciter excitation. But it will be better to ask the Manufacturer.

Excitor is having 3 phase rotor and the converted thro diode as DC to main rotor field supply

Great! So, how did the phone call with the manufacturer go?

Have you checked the rotor-excitation-diodes ? These diodes convert the AC voltage from the excitation-rotor in to a DC voltage to make a constant magnetic field in the generator-rotor.

These diodes are physically mounted on the generator or excitatory rotor. They rotate at the seem velocity as the rotor.

When these diodes are broken (open circuit), the excitatory-rotor voltage will not feed / supply to the generator-rotor coils with energy and these coils will make no magnetic field.

Wish I could be there to check rotating diodes, fuses, and connections...

Ha!

As long as the diodes are polar aligned, he'll be fine.

Doide were checked along with socket terminal found OK AC supply is getting converted to DC

SADASIVAM

Are those OEM diodes, and did you check the fuses and all the connections? The rotational forces are very high and can cause temporary changes to anything that is spinning, then everything reverts to "normal" when the shaft is at standstill.

How can you be certain that the "...AC supply is getting converted to DC..."? There's no way to verify that unless you have a flux probe in the air-gap, and if that were true then your generator would have output.

Only thing left is your instrumentation; you did use an independent meter on your output terminals, didn't you?

We had a strange problem once with a rebuilt machine during startup.

Turned out to be pigtail leads (large bare braid) on the diodes which 'bent' while running, thus grounding to diode case bracket. During coastdown, the pigtails would bend back, so all static tests passed.

See [also]:

http://www.dieselduck.info/machine/03%20electricity/flashing_generator.htm

Of course it is not generating voltage, you need to hook the engine back up to it.

During Separetely Excitation test, what was the voltage generated for 12 V DC Excitation ? If the voltage is any thing lesser than Rated Voltage then the problem is with the Excitation Circuit ?

Have you done any rewinding ?if you have done rewinding of Ex Stator or Main Rotor check that adjuscent pole is of different polarity..

You have checked all windings for static tests and the test results seems to be ok except the IR of 0.3 MOhm, I feel this is too low..try heating the Alternator through the External Source, which may improve the Insulation Resistance..

Check the Fuses..

Regards,

Vishram LELE

No rewinding done on excitor and diodes were checked seperately giving AC to check DC output.Heating of windings done to 5 Mohms. Control panel is at site with customer

Regards

Sadasivam