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Onan 4BGEF J30981E Need Production Order and Wiring Diagram


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  #11  
Old 11-10-2017, 07:49:08 PM
len k len k is offline
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Default Re: ONAN 4BGEF J30981E Need Production Order and Wiring Diagram

Yes that is a current transformer for boosting voltage to maintain votlage as you increase load.

965-0530 service manual is the correct one, (I looked in Onan's list of manuals 932-0112D for BGE spec E.)

Guess I stand corrected, looks like specs A-E, not A-C, were current transformer "regs" according to 965-0232 parts manual for BGE spec A-E
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  #12  
Old 11-10-2017, 07:58:03 PM
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Default Re: ONAN 4BGEF J30981E Need Production Order and Wiring Diagram

Not Hijacking the thread but have a question about the transformer for len k.
You say the transformer boosts power under load. How does that work? Does the generator put out a higher voltage and the transformer step it down?
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  #13  
Old 11-10-2017, 08:58:34 PM
Bill Aggenbach Bill Aggenbach is offline
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Default Re: ONAN 4BGEF J30981E Need Production Order and Wiring Diagram

Primary has two coils, each coil is in series with 1 leg of output. Varying current through each coil changes voltage in secondary that then goes to field. secondary has taps that can be manually selected to set output voltage to field which then regulates output voltage.
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Old 11-10-2017, 09:43:00 PM
len k len k is offline
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Default Re: ONAN 4BGEF J30981E Need Production Order and Wiring Diagram

Motorhead....... No, short answer is transformer senses increased load amps and uses it to add voltage to rotor. That overcomes magnetic issues in rotor/stator to maintain 120 output.

Long answer....
Without compensation, as draw more amps out the 120 V windings, stator voltage drops due to mostly magnetic issues **. Amps in stator likely make a reverse mag field that bucks magnetic field of rotor, thus drops overall magnetic flux. Remember voltage out a winding is proportional to rate of change of mag flux. So Less mag field = less flux = less flux change= less voltage. (hint: magnetic/electric analogy: mag field is like voltage, flux is like current).

AS add 120V load then voltage would drop. So to maintain 120 output a current transformer is added. It senses load current and adds the right amount of voltage to increase rotor voltage (and resulting rotor magnetic field to try to keep total mag flux from dropping). Taps are a trial and error way of picking the right amount of rotor voltage increase. This "trimming" is done at factory to compensate for production line tolerance variations between gens.

I say voltage booster, not voltage reg since current transformer can only increase voltage, not decrease it ( as you would want to do during load dump or high rpm). Electronic reg and magnaciter can reduce high voltage during high rpm (higher rate of flux change).




** I've seen these voltage sags and they are pretty severe. I ran my similar 7NHM with fixed 36VDC applied to rotor since it's electronic reg was dead. Got ~ 125V at no load, dropped to ~ 100 V at only ~40-50% of rated kw , eventually got it down to ~80V and still was not at gen's rated kw output ( my killawatt meter faded out at ~ 70-80V)

Last edited by len k; 11-10-2017 at 11:18:28 PM.
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Old 11-10-2017, 11:36:34 PM
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Default Re: ONAN 4BGEF J30981E Need Production Order and Wiring Diagram

I think I got most of the explanation len. You are quite the electrical wiz on these series sets!
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  #16  
Old 11-11-2017, 02:13:18 AM
len k len k is offline
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Default Re: ONAN 4BGEF J30981E Need Production Order and Wiring Diagram

It's a cross between physics class and 8 page crude info sheet from a old magnetics company sellling steel laminations from the 50's. I had to design a mag drive for a tuning fork instrument once (gyro). Wasn't happy with the crude 8 page info presentation.
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