Generac model 87a01481-s serial 831391

caveman272

Registered
Every time i shut down my gen. sparks come from the rotating diode pack (ie meat grinder) or (6 diode bridge rectifier) because a blown ( MOV ) (METAL OXIDE VARISTOR)of the field excitation circuit. if any one hear has my gen end can you look at yours and get the pt# off it this is a brushless gen 36kw 300/150 amp. Set up for 120/240 1 phase. IT makes the diodes blow but i have that pt# and lots of them. generac NO HELP !!! LOL I CAN GET SPEC FOR A MODEL T FORD BUT NOT A ANTIQUE GRNERAC GEN!!!
WOW GENERAC!!!!!!!!!!!!!!!@!!!!!!

THANKS CAVEMAN272
FOR ALL YOUR HELP
 

pegasuspinto

Registered
You can clip the MOV out and toss it. It helps but it's not needed. They usually fail OPEN and dead anyways.

Generac isn't the problem, it's your dealer sucks or something.

Just so you know, the MOV comes ON the bridge rectifier. It's not a separate part. I think you should need a G074244. I'm assuming it's the one with 5 push on terminals, perfectly square with the mount bolt in the middle
 

caveman272

Registered
a MOV protects the maine gen dc winding from a serge of energy like a lighting strike or surge from the brushless excitation alternator. If you think it is not need you need to learn electronic board level . unless you want to rewind the maine gen winding. I do know that it will still will work without it . it's not worth rewinding the generator because the coating on the windings were melded off form a surge of energy in the killavolt range and grounded to the frame . remember that the coating on the wires is about .050 inch thick or less . on my genset the 3 phase bridge rectifier are just single diodes 6 of them and a (MOV) wied across the DC output for the main windings.
 
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caveman272

Registered
If I can get all the specs for a model T FORD from FORD MOTOR CO. down to every bolt size. Then why can i not get it form generac thay are one of the largest genset co. out there. This puts a lot of strain on people that buy and sell used gensets or lost the docs in a fire. I myself would be willing to pay for the documents in return generac would be making money. but i can only speak for me.
 

pegasuspinto

Registered
The MOV most certainly does NOT protect the windings, it protects the diodes. Day-to-Day, it's not needed at all. For diagnostics, clip it out

When you said meat grinder, that's not the version with 6 individual diodes, to me.

If it's shorted, that's why your diodes are blowing. You're lucky it doesn't fry your exciter rotor.

I don't suppose yours looks like this?
 

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