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Onan MDJE 7.5 1978. Possble Burnt Windings


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  #11  
Old 03-10-2018, 02:57:21 PM
Vanman Vanman is offline
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Default Re: Onan MDJE 7.5 1978. Possble Burnt Windings

One potential advantage that generator windings have over those of an induction motor is that a motor started across the line undergoes heavy magnetic stresses, vibrating the windings every time it is started. A generator, on the other hand, only experiences those conditions when it is called upon to start a large motor. Probably not every time it runs, and maybe never, depending on the application.
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Old 04-15-2018, 05:37:51 PM
yachtgilana yachtgilana is offline
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Default Re: Onan MDJE 7.5 1978. Possble Burnt Windings

Thank you for all the suggestions. They have been helpful.

It was fun to find which wires were which, this is a double delta 518 wound stator.
There are 12 wires coming out, but the numbers have all come off! So the wife and I worked this out like Sudoku...

1+6=L1
2,4,7,12 all link together in a box
8+10=L2
9+11 joined
3+5 joined

I measured and did all the tests today, and found the rotating rectifiers, main rotor, exciter rotor and stator all perfect, maybe 15% off spec.

The main stator was down to ground on 6,3,8,11...So out it came.

I got a quote from a very professional looking rewinding shop, for rewind and encapsulate and bake for $240.00 so I'm going to send it in. I have rewound alternators before, and it was fun, but this time I have too many balls in the air.

There are some pics on our web page, gilana.org
here http://gilana.org/44_mallorca2/03summ05/summ05a.htm
and here http://gilana.org/89_4years/4years.htm

Pictures are more fun...

Will come back here and post my results...
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  #13  
Old 04-15-2018, 05:49:01 PM
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Motorhead Motorhead is offline
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Default Re: Onan MDJE 7.5 1978. Possble Burnt Windings

Love those TIGHT places that a boat has to work on the equipment. Got to make use of every last square Millimeter! Good thing you are a trim and fit guy! Is there a DETROIT diesel in your yacht?
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  #14  
Old 04-15-2018, 05:52:35 PM
yachtgilana yachtgilana is offline
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Default Re: Onan MDJE 7.5 1978. Possble Burnt Windings

Yessir. That is a 3/53 Detroit, also made in 1978 like the genset. Beautifully made equipment both of them!
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