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Generac Generators (SEARS, etc.)

Generac Stator Ohm test?


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  #21  
Old 01-28-2010, 02:45 PM
Jim Rankin Jim Rankin is offline
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Default Re: Generac Stator Ohm test?

If you don't have a circuit through the winding, it doesn't matter what voltage appears across the two ends, it won't power anything. It is a result of capacitive coupling.

Sort of like a static electric charge, it is lots of volts, but it can't do anything other than snap once. Usually an older analog volt meter will be enough of a burden to discharge the voltage faster than it builds up, but most of the newer ones aren't as much of a load and you see voltages that aren't significant.

Maybe you can find a used stator or a voltage regulator that will do the job.

I used to have a saved search for Basler on ebay that I checked and I would occasionally find stuff that was useful and a good deal. Trick is knowing what your requirements are and the specs on what you are looking at. Basler has a nice website with technical specs on their current and older models.
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  #22  
Old 01-28-2010, 03:25 PM
headpainter headpainter is offline
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Default Re: Generac Stator Ohm test?

Thanks Jim. That's why it is hard for me to get a grasp around electricity. My meter says one thing but it ends up being a false reading. After I got the reading that the stator was putting out the 25 VAC and hooked it back up and jumped it, its like the 25 VAC just disappeared. I am going to make a few calls to see if I can locate a generator salvage place unless anyone can help me in that area. I appreciate all the help.
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  #23  
Old 01-28-2010, 08:43 PM
headpainter headpainter is offline
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Default Re: Generac Stator Ohm test?

OK! I got the new rectifier diodes/brush set in the mail and put it in. And guess what! No change in the output of anything! So what does that tell you?
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  #24  
Old 01-28-2010, 09:50 PM
Jim Rankin Jim Rankin is offline
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Default Re: Generac Stator Ohm test?

It means you now have an extra rectifier assembly. And you should proceed with finding another stator, regulator or whole generator without worrying that you are spending money unnecessarily.

I expect you will find everything from whole generator ends on bad engines to ones like yours, it's just finding the right one that will make a good one out of two.

The only other thing you could look at is having that stator repaired or even possibly replacing that winding while leaving the rest alone. Just depends on how it's wound whether you could strip it out by hand and replace it. If it's buried in the slots along with the rest of the windings, then it's all or nothing.
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  #25  
Old 01-28-2010, 11:29 PM
headpainter headpainter is offline
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Default Re: Generac Stator Ohm test?

Thanks, Jim and all, I may be best served just getting another genset. What would you recommend as far as a quality genset? I had a good run with the generac but they are now owned by briggs and stratton. I saw a 8000 watt briggs at NAPA. I know to stay away from china junk. What are some good units? Looking for 5-8000 watts around $1000 or under. Thanks.
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  #26  
Old 01-29-2010, 10:27 PM
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Bill Geyer Bill Geyer is offline
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Default Re: Generac Stator Ohm test?

If those are the wires that show open on your meter, the open winding probably creates enough voltage to show on a meter (a sensitive instrument) but no real usable current to provide excitation. I think you stated that in an earlier post.
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  #27  
Old 10-31-2011, 09:37 AM
headpainter headpainter is offline
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Default Re: Generac Stator Ohm test?

UPDATE!!! I bought a Briggs and stratton 5550 genset new and it ran a bit over a year before it did the same exact thing the Generac did. I checked the excitation wires and no ohm at all. Ordered new stator for the new genset and it is going again. So it definitely was a bad stator in both gensets. Ordered new stator for Generac and it arrived damaged. Returned to supplier only to be told that was their last one and be on back order indefinitely. Both units are manufactured by briggs and stratton even though it carries the Generac name. Contacted Briggs about this re-occurring problem and they replied that over time, dust accumulation in the stator wirings can cause it to short out. I would think that the varnish epoxy coated wirings in the stator would prevent this. Anyone else had this problem and know how to prevent it. Stators are expensive. Thanks, Headpainter
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  #28  
Old 10-31-2011, 12:58 PM
Power Power is offline
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Default Re: Generac Stator Ohm test?

Keep your eye out for a used Onan. Quieter and better quality.

---------- Post added at 12:58 PM ---------- Previous post was at 12:25 PM ----------

I have seen what I believe to be the the same issue on Briggs powered units with other manufacturer's labels. Often the windings short out deep inside, where no dust can go. They are sold as USA units, but the gen parts were made in China. In my opionion, the insulating varnish is very thin and of marginal quality. Slight coil movement and insulation fails. I would soak new windings in varnish, perhaps overnight, in an attempt to consolidate them, stop internal winding movement, and provide additional surface protection.
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  #29  
Old 10-31-2011, 01:05 PM
Arkie Arkie is offline
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Default Re: Generac Stator Ohm test?

Quote:
Originally Posted by headpainter View Post
UPDATE!!! I bought a Briggs and stratton 5550 genset new and it ran a bit over a year before it did the same exact thing the Generac did. I checked the excitation wires and no ohm at all. Ordered new stator for the new genset and it is going again. So it definitely was a bad stator in both gensets. Ordered new stator for Generac and it arrived damaged. Returned to supplier only to be told that was their last one and be on back order indefinitely. Both units are manufactured by briggs and stratton even though it carries the Generac name. Contacted Briggs about this re-occurring problem and they replied that over time, dust accumulation in the stator wirings can cause it to short out. I would think that the varnish epoxy coated wirings in the stator would prevent this. Anyone else had this problem and know how to prevent it. Stators are expensive. Thanks, Headpainter
You stated:
Returned to supplier only to be told that was their last one and be on back order indefinitely
.
Just my opinion since you asked!
You have found out the hard way that Briggs (Generac) had a bad design in the stator windings for this model genny!
It was a heads up hint when Briggs was sold out of replacement stators! (demand exceeded supply)
Also the person that told you dust is the problem with the stator windings is blowing smoke onto you, dust and properly designed (wound) stator windings is a normal thing. His brain is dusty!
and
Anyone else had this problem and know how to prevent it.
Don't buy another and if the one you now have uses the same stator, sell it to your bro in law, but not on credit, or trade it for a Onan.
and don't hurt the messenger!
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  #30  
Old 10-31-2011, 01:17 PM
Power Power is offline
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Default Re: Generac Stator Ohm test?

Arkie - I believe there is a long lead on the rotors & stators because they are coming from China. Sears parts also sells these parts. They told us they are made in China.
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  #31  
Old 10-31-2011, 04:52 PM
Arkie Arkie is offline
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Default Re: Generac Stator Ohm test?

Just thinking if it were mine and only the exciter winding is bad I would think about looking at the DPE output AC voltage in the service manual, or check the output voltage of the good same type gen he now has and the DC voltage going to the brushes and then get a filament transformer (power transformer) with the correct voltage and wattage rating and connect the primary to either the 120v or 240vAC and the secondary to the existing diode pack and let er rip. (or look for a variable output external exciter regulator power supply)
I suspect his DC voltage for 125vAc is around 24 to 36volts DC and the transformer would have to be about 200 watts. Bet he could run a 4000 watt load easily using such once he corrected his output to around 130vAC!
I have a variable voltage power supply that I can use for such testing, variable from zero DC to 100volts at 10 amps.

If he did not have another gen or a service manual that lists the voltages he could maybe use 12v batteries in series until he seen the 120VAC come to around 120v then apply a load and see how much load it would carry using just athe battery power supply to get a idea. (3 12v batt for 36v etc.
Keep the battery's output fused at not over 10 amps while testing.

Stay safe!

You guys have any ideas about external regulator power supply just to replace the bad DPE winding?

Quote:
Originally Posted by Power View Post
Arkie - I believe there is a long lead on the rotors & stators because they are coming from China. Sears parts also sells these parts. They told us they are made in China.
Yes, and most likely the replacement parts have been discontinued (due to bad manufacture) and a motor re-wind shop would want more than a new gen price for re-wind, but the stator would be done correct, then Engine, if it were mine would go bad. (throwing good money after bad and whipping on a dead horse)
I've seen some 5kw gen heads on e-bay with different types of shaft coupling for replacement from couple of guys that looks good, but they require wiring to a receptacle panel. (recepts not on the gen head)
I sure would not buy another replacement stator even it were available after I seen two go bad for being reported by a Briggs tech being dusty as the cause of failure! Usually briggs won't say anything like dust being the cause in a e-mail, it's usually by phone only and it really a sales person instead of a tech.
(have to keep the gen in a enviromentally controlled filtered air room for non dusty operation and the stators may even be catching Asthma, due to rag-weed pollen.
nuff said!
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  #32  
Old 10-31-2011, 06:18 PM
Power Power is offline
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Default Re: Generac Stator Ohm test?

I believe gen parts still available - were last month from Sears - but $$$, and long wait.
I agree - would not waste time with gen - has a habbit of blowing exciter windings too. From what I can see, the Briggs engines are good and hold up quite well. NOISEY as heck, tho. Your thoughts on another gen for engine are valid. I believe both those units use the briggs tapered shaft.
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  #33  
Old 10-31-2011, 07:21 PM
K D Redd K D Redd is offline
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Default Re: Generac Stator Ohm test?

The taper on the engine shaft should be a SAE J609A or B. If you will look in a Northern tool catalog or on-line the have complete brushless generator heads in 3500, 4500 and 6500 watts. Yes they are also made in China. I do not know what Briggs/Generac is getting for the stator but you can buy the whole 6500 watt head for $350 plus shipping.

Kent
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  #34  
Old 10-31-2011, 07:25 PM
Kevin K Kevin K is offline
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Default Re: Generac Stator Ohm test?

Quote:
Originally Posted by Arkie View Post
You guys have any ideas about external regulator power supply just to replace the bad DPE winding?
I guess it depends on if the DPE winding is shorted or open. A shorted DPE winding means the stator is toast. An open DPE winding offers possibilities.

The DPE winding is wound such that an increase in load on the generator results in an increase in the output of the DPE winding, which maintains the voltage on the generator output. If we were just to put a transformer on the output, run it into a bridge rectifier, and feed it to the field, we would have no regulation to speak of.

In the UR generator ends, Onan pulled voltage off one of the output windings, ran it through two series reactors to limit the current, then regulated the output with SCR's switching current on and off through the field. This scheme would not work without the series reactors to limit the current, and custom wound reactors (really just series inductors) are expensive.

The first thing to do is use a variable DC supply to power the field. Adjust the output of the supply to hold the generator output voltage steady as the load is increased, and record the readings. Once the power requirements of the field are known, we may be able to build something. Assuming we are pulling 120v or 240 volts from the generator output, if a standard transformer can be found with an output voltage slightly above what is needed for the field, the transformer can be followed by a bridge, filter cap, and a dissipative regulator that would regulate the field voltage to maintain the generator output. Maybe with that same transformer, we can then use Onan's SCR regulator, since the output of the transformer would not be high enough to fry the field winding.

Whatever you do, you would be investing a lot of time in something that is not directly adaptable to another brand.
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  #35  
Old 10-31-2011, 10:15 PM
Arkie Arkie is offline
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Default Re: Generac Stator Ohm test?

Quote:
Originally Posted by Kevin K View Post
I guess it depends on if the DPE winding is shorted or open. A shorted DPE winding means the stator is toast. An open DPE winding offers possibilities.

The DPE winding is wound such that an increase in load on the generator results in an increase in the output of the DPE winding, which maintains the voltage on the generator output. If we were just to put a transformer on the output, run it into a bridge rectifier, and feed it to the field, we would have no regulation to speak of.

In the UR generator ends, Onan pulled voltage off one of the output windings, ran it through two series reactors to limit the current, then regulated the output with SCR's switching current on and off through the field. This scheme would not work without the series reactors to limit the current, and custom wound reactors (really just series inductors) are expensive.

The first thing to do is use a variable DC supply to power the field. Adjust the output of the supply to hold the generator output voltage steady as the load is increased, and record the readings. Once the power requirements of the field are known, we may be able to build something. Assuming we are pulling 120v or 240 volts from the generator output, if a standard transformer can be found with an output voltage slightly above what is needed for the field, the transformer can be followed by a bridge, filter cap, and a dissipative regulator that would regulate the field voltage to maintain the generator output. Maybe with that same transformer, we can then use Onan's SCR regulator, since the output of the transformer would not be high enough to fry the field winding.

Whatever you do, you would be investing a lot of time in something that is not directly adaptable to another brand.
Very good explanation! Even though the DPE winding is checking open now it could also have shorted turns internally from the previous fault and eventually slowly overheat, smoke, flame and all wasted!
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  #36  
Old 11-01-2011, 10:56 AM
Kevin K Kevin K is offline
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Default Re: Generac Stator Ohm test?

The DPE winding, typically wound out of phase with the output windings, is most likely wound in different slots on the stator. Could it be removed without damaging the output windings?
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  #37  
Old 11-01-2011, 04:39 PM
Power Power is offline
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Default Re: Generac Stator Ohm test?

The DPE winding, typically wound out of phase with the output windings, is most likely wound in different slots on the stator. Could it be removed without damaging the output windings?
Yes. Separate slots, easy to do. In fact, because winding is so small, would be possible to hand rewind.
Here is a picture of a similar one -Briggs powered Sears. As you can see, I had DPE rewound, windings tied down and stator dipped. This one failed afer 5hours! Was loaded max 60% powering 2 radios. I think what did it was cycling - constant loading & unloading when operators hit transmit keys.

In my opinion, the Chinese windings are thinly coated with a very soft (water based?) varnish, and not properly consolidated. Movement caused by load changes damaged varnish and windings shorted. I think if gen was powering a steady load like lights, it would have been ok.
I had rewind shop tie down windings and dip stator. Hopefully that will stiffen things enough to prevent recurrance.
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