View Full Version : Inverter Power Outlet Overvoltage

02-28-2013, 05:42 PM
The other day we were heading down the highway and the wife wanted to know if she could plug in her new warming pad and I told her that I thought so, The next time we stopped I took my trusty little meter that shows the voltage in the line and plugged it into the outlet closest to the microwave and it pegged at over 130 volts.Oops. I then plugged it into the outlet next to the dinette table and it still went to 130+. Checked them when we were plugged into shore power and they were ok.Needless to say she didn't get to use her warming pad while we were cruising highway.

So now,what's happening and how can it be fixed?

Will Procter
02-28-2013, 07:30 PM
If it's a modified square wave (MSW) output type inverter (usually the less expensive type) instead of a pure sine wave type, it probably fooled your meter. Meters don't read a MSW output very well. Your meter read correctly when you went to shore power because electrical service is a pure sine wave

02-28-2013, 09:12 PM
Will beat me to it! The inverter you have must put out a modified sine verses a pure sine wave. When you checked the outlets when on shore power and it was Okay that's because the public utilities is pure sine wave. The meter you used did not read true "RMS" voltage. The inverter was actually putting out 120 volts but the meter wasn't able to correctly read it. To read the voltage from a modified sine wave inverter you will need a different meter that will read true "RMS". There isn't anything wrong with you inverter.


02-28-2013, 11:54 PM
PS A Pure Sine Wave Inverter likely will not be repairable unless sent back to the manufacture and a long turnaround time! If you don't have the need don't bother! My SAMSUNG LED Television doesn't care.