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Generators & Electric Motors General Discussion

Slip Rings and Voltage Regulator Question - resurface and retrofit.


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  #1  
Old 09-02-2011, 01:53:24 PM
Freefall Doug Freefall Doug is offline
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Default Slip Rings and Voltage Regulator Question - resurface and retrofit.

I have two questions regarding my now not working generator, one involves fixing or retrofiting something for the slip rings, the other testing the voltage regulator.

The generator is a MultiQuip GRF-5RZ, 5kw surge, 4kw continuous generator, with a 10hp Wisconsin-Robin engine. You might have seen my post about killing the generator when I turned it off under load. The generator was a rental at one point, and I think it was pieced together from two different rental units. It has lived a hard life!

I want to rebuild and get it making power well again, the engine seems to run well, but it is a little weepy with the oil.

First the slip rings. The slip rings on the 5000W MultiQuip GRF-5RZ that I have are pretty torn up. They are pitted and scratched, not really sure what happened to them in its life.

MultiQuip wants 100 bucks for new Slip Rings. Is it possible to have these put on a lathe and smoothed out. The brushes would need to go a little further out to contract but I don't see an issue with this in theory. How do the slip rings work any way?

The second, the voltage regulator, I think I may have fried this turning the unit off without disconnecting the load. It was putting out good power 120/240 before this blunder. Afterwards it was putting out less than one volt on each winding, and I couldn't flash the field to get it going again.

Is there a way to test a voltage regulator?

They want 200 bucks for a new one!!! I don't want to replace if it isn't shot, and I don't really want to spend 200 bucks. Is it possible to retrofit a voltage regulator from another generator, or test components inside this one and replace? I am pretty handy with a soldering iron.

Maybe I should cut my losses, but it seems like it could be a great backup with only a little work.
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Old 09-02-2011, 02:32:16 PM
Jim Rankin Jim Rankin is offline
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

Don't wory about the sliprings yet, work on the regulator first and see if you can get past that without breaking the bank.

If they aren't out of round, just pitted and scratched, the sliprings can usually be tuned up with a coarse stone held steady against the spinning ring until it has no large divets left. Then use progressively finer grits to finish it to an almost mirror finish. There are small stones mounted to a handle made just for this, or you can probably find something that will work. I have even used a sharp file on a really bad one in an automotive alternator. BE CAREFUL, if your stone or file grabs the ring, it can hurt you and destroy the ring!

If they're out of round, they can usually be trued up with a lathe or a grinder on a lathe. For very large machines, there are grinders to do this job in the machine, but for small generators, the rotor is removed and put into the lathe.

Not knowing anything about your generator, the most difinitive test to see if it's fixable is to excite the field with a battery and see what voltage you get out of it. Check between lines (240 volts) and from each line to neutral (120 volts) and make sure the values you read are proportional. L-L voltage= 2xL-N voltage and both L-N voltages are equal etc.

If all this checks out, then the problem is in the regulator and exciter system. There may be diodes, capacitors etc keeping it from working other than the regulator itself.

There is usually a way to bench test a regulator if you can supply a reference voltage and monitor what the regulator output does in response.
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Old 09-02-2011, 02:54:05 PM
Wayne 440 Wayne 440 is online now
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

Quote:
Originally Posted by Freefall Doug View Post
...I am pretty handy with a soldering iron. ...
So make your own.


http://www.qsl.net/ns8o/vreg.JPG

Here is a diagram for a regulator. NOT my work, use at your own risk etc...
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Old 09-02-2011, 05:41:15 PM
Freefall Doug Freefall Doug is offline
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

I am more handy and desoldering stuff and replacing, but I might swing that.

Regarding applying current to the field. I am guessing that I would do this at the two brushes that ride on the slip rings?

I tried flashing with 120 out of the new generator that I bought with this wacky setup I saw on the internet involving some light bulb bases and such. I also tried flashing the field with the hand drill method, no change in voltage output.
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Old 09-02-2011, 06:20:47 PM
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Talking Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

Quote:
Originally Posted by Freefall Doug View Post
I tried flashing with 120 out of the new generator that I bought with this wacky setup I saw on the internet involving some light bulb bases and such. I also tried flashing the field with the hand drill method, no change in voltage output.
That is just so much BS....If you want to flash a Field, do it the CORRECT way, and use a DC Source, across the Rotating Field Winding, either thru the Brushes, or if it is a Brushless Genend, thru the Stationary Exciter Winding.
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Old 09-02-2011, 06:22:04 PM
Wayne 440 Wayne 440 is online now
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

To "flash" the set isolate the brush connections and apply a small battery to them.
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Old 09-02-2011, 07:03:53 PM
Gunny Gunny is offline
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

If you applied 120VAC to the slip rings/brushes, you might have let the magic smoke out.

Magic smoke being what makes generators and motors work. It gets out and they don't work anymore.

Use your ohm meter and see what you have for resistance between the slip rings, with the brushes out or the regulator disconnected. Would think somewhere around 30 ohms to be appropriate. Anything a lot more or less not good, check to ground (the shaft). Should read OL open circuit, no continuity.

Flight Systems can test/repair your regulator.
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Old 09-02-2011, 07:04:22 PM
Kevin K Kevin K is offline
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

I think the first thing to do is bypass the voltage regulator and see if you can get any output. If you have a variable voltage supply that can handle a few amps, this is easy to do. Disconnect the wires to the brushes, then connect the variable supply to the brushes. Start the generator, slowly bring up the voltage to the brushes, and watch the AC voltage at the output. Let it run for a while outputting 120 volts with no load. If this is OK, apply a load and watch the output voltage. You will probably have to increase the voltage to the brushes to bring the output voltage back to 120 volts. If you can get it to run for a while with a reasonable load, say 1000 watts, the rotor and stator are probably OK.

If your generator uses a quadrature winding to feed the voltage regulator, check out this thread:
http://www.smokstak.com/forum/showthread.php?t=85631
You may be able to make your own regulator cheaply.

Do you have a wiring diagram for your generator? If you do, please post it. This would help us answer your questions. Without the diagram, we are making a lot of assumptions that may not be valid.
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Old 05-14-2017, 10:22:44 PM
lnytns456 lnytns456 is offline
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Default Re: Sliprings and Voltage Regulator Question - resurface and retrofit.

Good evening all, I was wondering if this issue was ever resolved or not, and what, if any would be the voltages at the wiring points for the AVR as I have this same generator and the regulator has been pretty much smoked to the point that the epoxy covering the actual pc board was shattered off of the board (My uncle said that the AVR might be bad).... I'd like to find out what the voltages might be so that I can possibly formulate a possible replacement, or retrofit another one into the circuit to get it to function properly.....
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