12 lead generator running at 3600rpm ?

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K8MHZ said:
I guess I missed the diesel part. I was assuming a '454' would be a gasoline engine..
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The "454" number doesn't mean much. That was me picking 454 as an example. The OP said "big block chevy". I was thinking the unit was a DIY with an automotive engine mated to a used alternator. However, a not so common but factory 100kw unit uses a 502 GM industrial engine - maybe that is it.

But then again I don't know - so figured I better quit guessing. The OP will tell us if we need to know.

Ice
 
Phil Corso said:
what about the 'connections' comment? Easy enough to check, yes!
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You mean this statement?
Phil Corso said:
... The same 3 winding-pairs used for Zig-Zag, single-phase operation, are used for 208V, 3-phase operation! Pehaps while it operated single-phase one of the six windings was open-circuited and went undetected! Did you compare the phase-resistance of each pair?
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I don' tknow. I have plenty of experience with generation. But is is all from the terminal box out. I can't tell you much about how they are internally wound. I've never seen any wiring diagrams that change the gen from a two pole to a four pole.

ice
 
Just bumping this to the top to see if the mystery was ever solved. Why was a four pole alternator being driven at 3600 RPM in order to get 60 Hz output?

Either the alternator was somehow actually operating as a 2 pole machine, or somehow the frequency measurement/control was wrong, or the RPM measurement was wrong, or some even stranger thing.

-Jon
 
Seems I am very late to this party.

I have never seen this scenario in real life. However, my suspicion is that the only way for this scenario to occur is that it has a 4 pole rotor, with each pair of poles wound in parallel with the other pair. One pair of poles' winding went open leaving this as a 2-pole machine. It had to be sped up to 3600 to get 60 Hz output.

The predictable happened and something flew apart. I am surprised the rotor itself did not come apart but it sounds like it will need to be repaired anyway. To confirm this theory check the resistance of the rotor and see if it is twice the specified value. If it is then repair the rotor and you should be good to go.

There were some large 12-lead 3600 RPM machines known as the Onan Techstar in the mid-80s. Some used a slant 6 Chrysler for 50 KW and some used a V8 IIRC for higher output. Some also ran at 1800 RPM but the high RPM ones were known for breaking down due to the high RPM and the loud noise was also a major annoyance. I think (you guessed it) cooling fans were one of their problems.
 
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