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Generator voltage drops underload, but RPM remains the same.

Generator voltage drops underload, but RPM remains the same.


Old 10-19-16, 06:36 AM
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Generator voltage drops underload, but RPM remains the same.

I have a 7000W diesel generator I use with a plasma cutter and welder. Today, the plasma cutter and welder started cutting out due to low voltage. They both have error indicators and both indicate low supply voltage. On the 240 outlet under medium load (15-20A) from the plasma cutter, the voltage would drop to under 160V. Yet the generator's RPM would only very slightly decrease. Usually, the generator bogs down for a second and the engine spits out a little black smoke (because it's diesel) before the governor catches the RPMs back up. My thought is the governor isn't the issue. It seems the generator isn't even giving the engine enough load for the governor to have to take any action. Does anyone have any ideas what's causing this? Is this the job of the voltage regulator? I mean, does the regulator dictate how hard the generator has to work to maintain voltage? If so, how would I test the regulator?
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Old 10-19-16, 07:50 AM
Join Date: May 2015
Location: USA
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First I would make sure you don't have a bad connection between the generator and the equipment (including possibly at the generator receptacle). Try measuring the voltage right at the generator, perhaps at a different receptacle if there are multiples.
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