I have 2 Kohler 7kw gasoline powered generators mounted on my Barth. Both came installed from the factory.

The one on the drivers side will put out 120 volts.

The one on the passengers side only puts out 92 volts. When I increase the RPM's the voltage goes down.

Any thoughts? How does one go about increasing the AC voltage on a generator? I thought the speed increase would have helped.

BTW - I ran both AC units, turned on all of the 120v lights to see if the load would cause the Kohler to choke. It didn't miss a beat and kept putting out 92v. I only did this for 30 seconds as lower voltage will increase the amp draw and could burn out an AC motor.

Bill, I'm outta my league here, and this is apples & oranges, but my Onan troubleshooting guide says 3 things ref: low output voltage:

1. Confirm/correct for proper operating RPM.

2. Check brushes & slip rings for shorts.

3. Contact a CERTIFIED service rep.

MAYBE #2?........

Some gensets will increase voltage somewhat if the RPM is increased, these have ferro-resonate regulators to control the voltage output. If it did, the RPM should be set to 1800 or 3600 RPM and then it should produce 120 volts +/- @ 60 Hz. If yours has a "solid-state" regulator, increasing RPM will not help, the output voltage will remain constant over a fairly wide range of RPM.

You probably can change the output voltage, look into the regulator box and see if the is a potentiometer or voltage adjustment rheostat. There may be several controls there so be careful and mark any control so that you can return to the original position if need be.

Make sure that you have set the output to be 60 Hz before you make any adjustment to the electronic regulator. (1800 or 3600 RPM)

Bill, since this was a radiology unit, it may be that one of the generators is a 3 phase set which when measured between the non neutral conductors (L1 L2 L3) would normally be a lesser voltage, like 102, 204, 408 etc..If its 3 phase, it should say so on an ID tag someplace.
My .02
Jack

How many and what color are the output wires?

My Kohler RV genset manual for 3.5 to 7.5 kw (with relay controller) says for low voltage:

1. Generator is overloaded.

2: Engine RPM set too low.

3. Faulty exciter voltage regulator

4. Poor stator coil connections. Use a clamp on ammeter and check each connection.

If you would like a scan of the voltage regulator testing procedure, let me know tonight, as tomorrow is the start of a Barth weekend. Any Supporting Member can have a copy for the asking, as well. The test requires a Variac.

I'd favor 3., as that seems most likely, especially since the voltage drops as RPM increases. (This could also indicate a short in the rotor, but that's generally fatal) 4. Stator connections can be a culprit, but they'd have to be in really bad shape to show no-load voltage that low.

However, it could also be an indication of chattering brushes on the slip rings - nearly worn out or a sticky brush holder - or grunge on the slip rings, or a broken slip ring.

Jack's idea of 3-phase power is worth investigating, but that genset would look and be placarded entirely differently from the other.

If you don't have a way to check frequency (older automotive meters had a clamp on for a spark plug wire that would measure RPM - you may have access to one), an electric clock will do - plug it in with the genset running for 15 minutes. The percentage of time difference, high or low, will indicate the difference between design RPM and actual.

BTW, if it were I, I'd remove the low-voltage genset, as one is plenty, and you're hauling around ~300 lbs. of dead weight.

Kohler brushes are really long-lasting. A Kill a Watt will give a freq reading that will translate to RPM.

My armchair hypothesis on the voltage dropping as the freq is increased is that a super weak output can't handle the increase in inductive reactance, which is goes up with frequency by 2 pi or something.

Our seldom-used Kohler straightened up and flied right once it got some good fuel system cleaner, all connections cleaned, and the rpm set.

Heck, removing one of those Kohlers would still leave you with more than you need.

quote:

Originally posted by bill h:
How many and what color are the output wires?

3: green - white - black

quote:

Originally posted by bill h:
Generator is overloaded.

check-nope

quote:

Originally posted by bill h:
Engine RPM set too low.

check-nope

quote:

Originally posted by bill h:
Faulty exciter voltage regulator

I measured 12-14volts at the exciter wire

quote:

Originally posted by bill h:
Poor stator coil connections. Use a clamp on ammeter and check each connection.

I removed the cover where the circuit breakers reside and measured the voltage before the breakers in case there was voltage loss across corroded connections inside the breakers.

quote:

Originally posted by bill h:
If you would like a scan of the voltage regulator testing procedure, let me know tonight, as tomorrow is the start of a Barth weekend. The test requires a Variac.

Yes - send me the scan please.

quote:

Originally posted by Jack:
...it may be that one of the generators is a 3 phase set...

Good idea, but this is not the case. I thought the same thing too, at first.

quote:

Originally posted by Rusty:
However, it could also be an indication of chattering brushes on the slip rings - nearly worn out or a sticky brush holder - or grunge on the slip rings, or a broken slip ring.

It might be. I was looking for a way to adjust the output by turning a screw or increasing rpm's - I was hoping someone would tell me..."Bill, there is a potentiometer/rheostat located inside the _________...." and I could try to turn it in or out.

quote:

Originally posted by MWrench:
You probably can change the output voltage, look into the regulator box and see if the is a potentiometer or voltage adjustment rheostat. There may be several controls there so be careful and mark any control so that you can return to the original position if need be.

Does anyone know where this box is located? I found 2 solid state units attached to the outside of the generator and did not see any adjustment points. Maybe I need to remove these boxes and check behind them as the adjustment might be hidden to keep a novice from messing with them.

quote:

Originally posted by Rusty:
BTW, if it were I, I'd remove the low-voltage genset, as one is plenty, and you're hauling around ~300 lbs. of dead weight.

Yeah. I was thinking of making a storage box back there instead. My thoughts on this extra generator was to get it running and have a spare - just in case the original died while using it... But the thoughts of "an ice machine" excites me even more.

Your generator controller box will have a plate with a number on it. The part number for the wiring diagram for your controller will be one digit higher. These were changed frequently by Kohler, so you need the exact one for your unit. Your local Kohler distributor should be able to help obtain info.

Try www.kohlerpower.com to locate a distributor and maybe even download some documents for your unit. Probably not docs for service tho.

Good Luck,
Mike Cebula

quote:

Originally posted by Bill N.Y.:
But the thoughts of "an ice machine" excites me even more.

Spoeaking of which, we have a little Magic Chef icemaker that runs off our solar powered inverter. Nothing to get excited about, but it makes ice. When we had a cord, we used our U-Line icemaker. It has been in almost daily use since the eighties, without missing a beat.

I have figured out how to increase the voltage of my Generator.

Camera Phone Pictures of My Kohler Generator





In the lower photo there are 3 potentiometer adjustment slots. These adjustment slots are located behind the "External AC Voltage Regulator" as noted in the top photo.

~~ First, make sure the engine speed is set at 1800 RPMs ~~

The top slot will increase the voltage when you turn the slotted screw clockwise.

The middle slot will decrease the surge in the lights. If you notice your lights surging, this adjustment will smooth out or eliminate the flickering altogether.

The bottom slot states that: "Adjustment determines the engine speed (HZ) at which the generator output voltage will begin to drop."

What this means is once all other adjustments are made, turn off the generator. Turn this screw counter clockwise. Start up the generator and turn the screw clockwise until the voltage just starts to drop and then stop turning the screw.

When set to this specification the generator will attempt to maintain normal output until engine speed drops below the min spec of 56.3 HZ. Which is the setting for 60 HZ operation.

The following is noteworthy.
1) I used an insulated screwdriver.
2) The plastic adjustment screw is slotted and can only be turned a maximum of about 340 degrees.
3) Electricity will kill you. Do not do this unless you are qualified.

I adjusted the top and bottom "POTS" and was able to increase my voltage to 120VAC and I have eliminated the slight surging of my lights from both of the generators.

Good work! Did you find a manual, or were there stickers on the genset?

quote:

Originally posted by Rusty:
Did you find a manual, or were there stickers on the genset?

I called several places until "Kinsley Power Systems" had mercy on me. They faxed me their diagnostic sheet for this "Kohl`lder Generator"

Kohler Older

His word, not mine