Voltage unstable on generator

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hockeyoligist2

Senior Member
The voltage was very unstable on a 277/480 V generator with or without a load. Constantly up and down, too fast for my Fluke, had to get my old analog meter.

The RPM's and frequency are holding steady. I replaced the voltage adjustment pot on the panel, the old one checked good but I had a new one handy. I adjusted the stability pot on the voltage regulator (Generac) and got it to within 20v, was 50+v. The gain pot doesn't affect it at all.

I can raise and lower the voltage with the panel control and/or the voltage adjust pot on the regulator. I'm thinking the regulator is bad. Anything else I should check before buying a new one? The Boss wants to be sure before spending $300.
 

SG-1

Senior Member
How can I check this? It is a very old generator, manual has been gone many years.
Use a multimeter with a function to measure the crest factor. This will be a higher end meter. I think it should be 1.4. This will tell you if the wave is distorted.
Use an oscilloscope to view the wave form.
A power quality meter would also work.
 

Besoeker

Senior Member
Location
UK
Use an oscilloscope to view the wave form.
That's what I would usually do for a power quality analysis. I can store and download the data for later calculations.
It may be overkill to establish whether or not a $300 part might be faulty. On the other hand, hockey could fit a new regulator and still have the same problem.
 
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nawao

Member
Location
Abuja - Nigeria
Troubleshooting brushless alternator

Troubleshooting brushless alternator

If is a brushless type alternator try the following:
1) Disconnect the excitation wires from the voltage regulator (usually F1+ ; F2 -)
2) Run the generator at no load condition.
3) Apply 12V from a car battery to the field terminals respecting the correct polarity.
4) Observe if the output voltage is steady or unstable.
5) If is steady the fault is in the AVR. Give us more details about brand, Manufacturer, etc.
6) If is unstable check the rotating diodes. Possibly you have a short circuited or open one.
 

ATSman

Senior Member
Location
San Francisco
Occupation
Self Employed
Caterpillar Forum

Caterpillar Forum

The voltage was very unstable on a 277/480 V generator with or without a load. Constantly up and down, too fast for my Fluke, had to get my old analog meter.

The RPM's and frequency are holding steady. I replaced the voltage adjustment pot on the panel, the old one checked good but I had a new one handy. I adjusted the stability pot on the voltage regulator (Generac) and got it to within 20v, was 50+v. The gain pot doesn't affect it at all.

I can raise and lower the voltage with the panel control and/or the voltage adjust pot on the regulator. I'm thinking the regulator is bad. Anything else I should check before buying a new one? The Boss wants to be sure before spending $300.
You may want to post this on the CAT site where they specialize in generators::D
https://caterpillar.lithium.com/caterpillar/

Tony
 

hockeyoligist2

Senior Member
Most likely find your answer here http://zillerelectric.com/forums/index.php

Generac forum for trouble shooting.
Thanks all, I just signed up on ziller. Waiting for a e-mail so I can post.

I checked and cleaned the brushes and slip rings yesterday. Didn't help.

nawao, It is a Generac 67680 regulator. Generac generator, but I don't have all the info on it with me. I'll try what you suggested Monday. Opps reread you post, this one has brushes.

This is the regulator http://www.partsfortechs.com/asapcart/bmz_cache/2/2cdacaaf1e28384e288dd540e599c836.image.733x550.jpg
 
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hockeyoligist2

Senior Member
Update

Update

I finally got back to the generator. Been a busy week with more important things. I adjusted the gain pot again and the voltage stabilized, 480v phase to phase, 277v to ground, + or - 1v. Checked it with 3 different meters.

Now the analog gauge on the control panel is going wild! 400v to 510v.

I am going to pull it over to some old, no longer used, equipment Monday and give it a try to see what it does under a load.

zillerelectric.com still won't let me post for some reason.
 
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