Generac 5500 Wheelhouse Low Voltage

[kicker92]

I need some help with my Generac 5500 Wheelhouse generator. I picked this unit up at auction, and althoguh it starts and runs, it does not produce voltage.

I hooked up a D-cell battery to the field leads while running to get the field established, but this did not solve the problem.

A voltmeter while the unit is running shows 1.5V on the 120V leads, and 3.0V on the 240V leads.

I've tried searching the forum, and haven't come up with many other options, so any helps would be appreciated.


Thanks,

Ryan

[Jim Rankin]

Most likely (fixable) problem is diodes in the exciter. For a brushless set (no brushes or sliprings on the armature), there are usually pairs of diodes on the armature and possibly others in the regulator.

[kicker92]

Hi Jim,

Thanks for the reponse. Do you know on this type of unit how to acess these diodes, and if there a way to test them before replacing?

I don't have a wiring diagram for this one, and closest diagram I can find is: http://www.briggsandstratton.com/pdf...0246_0_wds.pdf

Is the idea that if the diodes were bad, the field wouldn't charge?

[Jim Rankin]

Yes, most sets these days make the power for the main alternator field from the AC output. This is usually rectified in the regulator and the correct DC output is fed into the exciter field. The exciter rotor rotates in the magnetic field created in the exciter and this makes AC power which is rectified by diodes on the main rotor to convert it to DC for the main alternator field.

You may have a bad regulator, a bad exciter field (the stationary part of the brushless exciter), a bad exciter rotor (the small winding which rotates inside the exciter field), bad diodes between the exciter rotor and the main rotor field. Of all these, the one most fixable by most of us is diodes which are check-able with a common multimeter or test light, are commonly available and cheap. Mouser, Digikey, RadioShak etc will all have diodes available.

[Jim Rankin]

I know nothing specific about your set, but the diagram you link to seems to show a brush type generator unlike the brushless type I was referring to in my previous post.

In this case the only diodes are probably in the regulator board which is probably what is shown as "bridge rectifier" with a variable resistance across it at the top. It seems to be powered by a separate exciter winding ("exciter") which would be wound on the stator along with the AC circuits shown as "power" on the bottom section of the schematic.

I would suggest measuring AC voltage on the exciter winding as it comes into the regulator. If no AC there, flash the main field at the brush leads with 6-12 volts DC from a battery while measuring AC output. Observe correct polarity while flashing!

I expect you will get some significant AC output at least while your DC source is connected across the brush leads. It may be that it only needs a flash to restore the necessary residual magnetic field in the iron so that it can build up to full voltage.

If it will not make any voltage, then suspect brushes, sliprings or field circuit on the rotor. I doubt there is a problem with the stator (power) windings because of the small but symetrical "residual" AC voltages you report. (1.5 +1.5 = 3.0). You can check through the field by ohming (checking resistance) from one slipring to the other after lifting the brushes and placing paper underneath or even better, disconnecting the brush leads and ohming through the brush leads, brushes, sliprings and field circuit.

If the output builds up significantly while flashing, but falls back to the 3 volts when you remove the flashing connection, suspect the exciter winding and regulator components.

[kicker92]

I have to admit, most of this is new to me, so I'm trying to learn this carefully.

When you say to use the correct polatity when flashing the field, based on that diagram, would the red or blue go to the positive side of the battery?

I'd used a 1.5V D-cell battery to try to flash the field before, but I guess that wouldn't be enough. For the 6-12V source, what kind of amperage should I be applying?

Are we talking about a little 9V battery, or a car battery size charge?


Thanks again for the help!

[kicker92]

EDIT: I should also mention that i get full continuity between the red and blue leads, with no-resistance. I think this would indicate that the field wiring is intact?

[K D Redd]

From the diagrham, red is positiveas it is connected to the cathodes of the bridge rectifier and the blue is negative connected to the anodes of the bridge.

Kent

[Jim Rankin]

To flash the set effectively, you need to access brush lead wires 1 (negative) and 4 (positive). I expect you may be able to do something with a drycell battery if all it needs is a flash, but if you have a problem, it may take an automotive battery to provide enough amperage to supply the field long enough to fully build up voltage, measure it etc.

[kicker92]

Ok, so I tried flashing the field with a 9V dry-cell with the positive side connected to the red leads, and sure enough, it jumped from 1.5V output to about 5V.

The little battery didn't seem to have enough omph, so i descided to start it up, and touch those leads to the car battery, for less than a second. The RPM's instantly dropped, and it started charging!

I measured about 65V on the output leads, and within about 5 seconds, the generator started smoking. (from the generator case, not the motor!) I panicked and shut it off before it cooked something.

Tried restarting the unit later once it'd cooled off, and it fired up to life, you could hear the engine working hard to turn the generator, and same result, the thing started smoking and smelling like burning insulation after only a couple of second.

I checked the field coil, and it still has continuity, so at least thats intact. What should I check on this, or is the unit likely toast?

[Jim Rankin]

Sounds as if you have a fried stator. I was hoping that the symetrical residual voltages meant the stator was good.

If you can lift the connections at the neutral point between the two 120 volt circuits and isolate the whole thing from the frame, then you can check resistance and continuity through the coils and also check for shorts to ground. It looks as if disconnecting the 6 pole connector will do this for you. You can then ohm through from grey to black and red to blue and check the windings.

Since this isn't a reconnectable set, I would doubt there was a mis wired connection, but sometimes a receptacle has been replaced and wired wrong etc.

It would be a long shot if it were still salvagable. You might investigate the cost to rewind the stator if the rotor is good. The only thing slightly different from the normal motor is the exciter winding in the stator. It may be that it is similar enough to a single phase motor stator that a motor shop would have no trouble handling it.

[kicker92]

Ok, looking back at the wiring diagram:
http://www.briggsandstratton.com/pdf...0246_0_wds.pdf

I realize that I've screwed up. When I was "flashing the field", was connecting power to the Red(22) and Blue(11) leads, instead of the Red(6) and Blue(2) ones.

I thought there were the correct ones since the ohm meter showed continuity between these two leads. there was no continuity between any other pairs of the Blue(11), Red(22), Black(33) or Grey(44) leads.

Would it be possible if the Red/Blue side of the generator is toast, to still salvage output on the Black/Grey side? It would only be 120V, but better than nothing.

Found out that a new stator or rotor is way too expensive for this unit, but the bridge rectifier is still availible if that needs to be replaced. When I pull this apart, is there any particular places to look for shorts, or just try to spot a burnt patch?


Thanks for all the help!

[K D Redd]

With either Number 2 or number 6 disconnected from the bridge, you should have continuity when measuring wires 2 and 6. The bridge should be available from your nearest Radio Shack. Might have to modify the mounting. If no continuity between 2 and 6 you have a bad rotor. The voltage you are measuring is probably from the residual magnetic field.

Kent

[kicker92]

http://www.briggsandstratton.com/pdf...0246_0_wds.pdf

Ok, opened it up yesterday and heres what i've found:

1.) Stator wires near the bridge and charred, the insulation/varnish is definatly burnt off.

2.) There is continuity between the #2 and #6 wires for the field, minimal resistance

3.) The grey 44 lead shorts to ground. None of the other (11,22,33) wires connect to ground.

4.) It looks like the rotor has contacted the stator, there is one damaged / charred spot.


Overall, it looks pretty much like junk at this stage. It's too bad, because it's a pretty slick design with the removable fuel tank, big wheels, etc.

Maybee I'll be able to use the motor and frame for something else, or come across soem used parts one of these days. It's just not worth $450 for a new rotor and $350 for a new stator from the dealer.

[Wayne 440]

Check *-bay for a generator 5-6 kw generator end. They are often available for about half the price you quoted.

[REWSR]

Can anyone help with the amount of flash voltage required at the rotor to establish residual magnetism for the generator to start operation? Can the voltage be supplied when the rotor is not running?

Has anyone used the newer recommended bridge rectifier block assembly #91825a that replaced the #91825 assembly? I've also seen a recommendation for a #091825a for the bridge rectifier block. Are these all the same, or has there been a correction/update?

There is a part in the bridge rectifier that lies between the diodes that appears to be some sort of a protective device, possibly an MOS metal oxide semi-conductor. Anyone know what it is and where it can be purchased?

Thanks for your help,
Bob

[Don Smith]

Can you post some pictures of the gen head you have on the unit. I have a number of generacs in my bone yard Might be able to help you Don