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Author Topic: Wiring problem  (Read 6003 times)

brianhoward

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Wiring problem
« on: May 29, 2008, 05:13:03 PM »
I know this isn't a lister, but the gen end is somewhat similar to other belt drive units.
I have a Kubota 6500 generator switchable from 120 only to 120/240. When i switch it to 120/240(no load), the engine bogs down as if it is shorted. If I remove the output wires(4) from the gen end, I get 120 across each set, but if I connect the windings as for a common neutral, I get sparks and the engine bogs. I cannot find a grounded or shorted winding.
This is a Kubota GL6500S Lowboy which is their own unit. 2cyl, water cooled, belt drive, 3000 rpm engine - 3600 rpm generator. The voltage selector is a 3 pole, 2 throw toggle that parallels the windings for 120V and serieses them for 120/240. It works fine on 120. I have another identical unit that works fine in both ranges. The problem occurs when the windings are connected with a common neutral for 240V. What do the experts say?
Thanks, Brian
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Doug

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Re: Wiring problem
« Reply #1 on: May 29, 2008, 09:56:39 PM »
Sounds like one leg is reverse phase when he tries to connect for 120 opperation.

I would not be doing that on a running set.

That is an expensive alternator to repair/replace if damaged
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brianhoward

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Re: Wiring problem
« Reply #2 on: May 29, 2008, 11:16:17 PM »
Yeah, it does sound like reverse. The wiring is correct by the diagram, and the same as the other unit. Haven't  figured posting a JPEG on this site yet, or I would post the print.

Brian
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Doug

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Re: Wiring problem
« Reply #3 on: May 29, 2008, 11:35:20 PM »
Simple test for polarity.

With what you think are the neutral tied together and the L1 connections open start the generator and measure the voltage if you read 240 you have it wrong.

Shut it down swap two ends and repeat if you measure 0 volts you have it right.
Make your connections and retry the set measure and confirm you have 120 vac.

Doug
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brianhoward

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Re: Wiring problem
« Reply #4 on: June 02, 2008, 04:17:29 PM »
Lets call the connections on the gen A,B,C and D. A-B is one coil, C-D is the other. Sensing for the AVR  is from a tap on the C-D coil. They connect A and C, B and D (parallel) for 120V. B and D are grounded to the frame and connected to the plug as neutral. (this works fine) For 120/240 they connect B and C as neutral with A and D as line.(this bogs the engine down) This is thru the voltage select switch on the panel. With the output disconnected from the gen, I get 120V line to neutral with the windings paralleled. If I connect B to C (grounded or not) and start the diesel, the engine bogs down.
If I connect B to D, I still get 120V across each coil, but I get nothing across A and C. I can't find 240V anywhere. ???
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Doug

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Re: Wiring problem
« Reply #5 on: June 03, 2008, 02:36:15 AM »
Hmm.

Is it possible there is a ground you need to disconnect on " C " or something?

Check with a meter and see it there is any internal grounds on both sets of coils when disconnected if you haven't already.

Not sure what else to look for, sounds like you have the right connection.

Doug
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brianhoward

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Re: Wiring problem
« Reply #6 on: June 03, 2008, 03:43:52 AM »
B only is grounded. D becomes grounded when the windings are paralleled. My  Fluke meter cannot find any ground in any of the stator or rotor windings.

The REALLY odd thing is that my other (identical) unit works fine on both setting with the same wiring setup!!
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trigzy

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Re: Wiring problem
« Reply #7 on: June 03, 2008, 07:11:56 PM »
I would bet the switch is internally defective.  You'd have to remove it from the circuit and check all connections for proper open/close cycles.

Steve
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brianhoward

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Re: Wiring problem
« Reply #8 on: June 04, 2008, 07:17:55 PM »
Quote from: trigzy on June 03, 2008, 07:11:56 PM
I would bet the switch is internally defective.  You'd have to remove it from the circuit and check all connections for proper open/close cycles.

Steve
Nope. Does it with all output wires unhooked from the gen. It must be a problem in the stator windings, but what??

Brian
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brianhoward

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Re: Wiring problem
« Reply #9 on: June 12, 2008, 04:34:30 AM »
Sorry for the delay,Jens
I just checked the stator coils - they both read 1.0 ohm, on my other working unit, they read .9 ohm. The book says .33 ohm. This is within the range of error of my meter and leads. I cannot find a short to ground on either. It does still bog with the wiring disconnected from the gen, but hooked for 240V, but not when in parallel for 120V
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brianhoward

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Re: Wiring problem
« Reply #10 on: June 12, 2008, 06:38:07 PM »
My thoughts exactly, jens. The regulator seems to work fine, but it does sense from the winding that is reversed when you series it. I will try another reg and see. When the engine bogs, the output voltage drops off. These things are sent to try us. I don't NEED the generator, but the not knowing really bothers me.

Brian
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