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Grounding thru the end support armature bearing


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Old 10-09-2015, 07:14:09 AM
sdowney717 sdowney717 is offline
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Default Grounding thru the end support armature bearing

http://www.windpowerengineering.com/...ator-bearings/

I have put this gen end back on the engine.(MCCK 6.5 spec C) I did put some spray paint on the field frame and end housings but was wondering if I should loosen it back off a little and scrape the ends clean of paint where the parts meet together to ensure a better electrical ground. I measured the ohms between field frame and engine at 0.2 ohms thereabouts, but you know that could be grounding through the end bearing which would not be a good idea. Other thought was add a wire from the end bell frame (that holds brushes) to the field frame cylinder (that holds the field coils) to ensure a good electrical path.
What do you think?

relevant pic showing a painted end. And also the strings were rotten so I used zip ties.
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Old 10-09-2015, 07:29:45 AM
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Default Re: Grounding thru the end support armature bearing

It's normally not a problem on smaller generators. But yes there can be a recirculating current buildup in the rotor which seeks ground through the end bearing or the engine bearings.

Think of a motor brush. Mount one that acts against the shaft end and and is grounded. Done deal.

About 30 some years ago Chrysler had a rash of complaints of popping noises in AM radio stations on some car model. At the same time these cars were having rear axle bearing failures. It turns out that the rear axle was insulated on rubber spring bushings and static was building up from the tires spinning and it arced through the bearings to find ground through the drive shaft and parking brake cables. The fix was a ground wire from the axle to the body. Two problems solved.

*A company I worked at had a machine that had a timing belt driven drive spinning at 3450 rpm. In winter the operators hated to use it as they'd get zapped occasionally. Maintenance went through it looking for the typical electrical faults to no avail. I watched it one day and it hit me. Static buildup on the belt as it was in reality acting like a nice Van de Graf generator in the low humidity environment. I had them install a grounded carbon motor brush contacting the shaft end on the motor. No more zapping.
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Old 10-09-2015, 09:31:58 AM
grif grif is offline
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Default Re: Grounding thru the end support armature bearing

They also made a bearing cap with an internal spring and "button" to ground the rim and tire, along with some anti-static powder you put in the inner tube. (remember those ???)
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Old 10-09-2015, 11:30:07 AM
sdowney717 sdowney717 is offline
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Default Re: Grounding thru the end support armature bearing

I did back it off a little and scraped the mating surfaces where the field frame meets the engine. Then I bolted it back up tight and sprayed some paint over top. This makes me feel a little better about the grounding. Consider the negative battery cable bolts to the field frame, so you do want a good ground to the engine and the brushes.
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Old 10-09-2015, 01:14:47 PM
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Default Re: Grounding thru the end support armature bearing

Quote:
Originally Posted by grif View Post
They also made a bearing cap with an internal spring and "button" to ground the rim and tire, along with some anti-static powder you put in the inner tube. (remember those ???)
Mercedes used that on the front wheels. The front spindle shaft was drilled and a copper plated flat spring contacted insied the grease cup.
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