Hi Guys,
This problem doesn't really fit into the other categories, but I figured y/all might be able to assist. I finally broke down and bought an inverter generator. I have a pair of non-inverter gensets that I use since I live in Hurricane Alley and power loss can be for several days if we get hit in the wrong way. However, non-inverters don't produce very clean power. Harmonic distortion can get uncomfortably high (25%) for electronics. An inverter is supposed to make clean power that's safe to use for anything. I found a good deal on a Wen unit, the GN400i. I tested it out this weekend for the first time. Started right up. Checked AC voltage which clocked in at 124.5 volts stable. So far, so good.
I checked to see the Hz output. I have a True RMS DMM that I used. I was expecting a clean 60 Hz signal. Well, that's not what I got. The DMM started jumping from 1 KHz all the way up to 9 KHz. That could not be correct, obviously. Thinking that the DMM might be malfunctioning, I tested the nearby wall outlet. It showed 60 Hz. I fired up my non-inverter genset and it showed a steady 59.7 Hz. So I knew the DMM was working fine.
I added a small load to the inverter to see if that would settle the Hz down so I could get a reading. Nope, no luck. I tried all of the outlets on the inverter, same reading. I tried different holes in the outlets, no difference.
I've seen DMMs have trouble reading Hz on gas generators before. Using a non-TRMS DMM on a non-inverter makes the meter go nuts when set to Hz. However, a True RMS meter is not supposed to be affected by that. I do have a non-TRMS DMM I could try to see if it gives me a stable Hz reading. But typically, high harmonic distortion is what makes reading frequency on non-inverter gensets difficult. The inverter should not have a lot of that, though.
I'm really stumped here. I don't know if I have a bad inverter board or bad cap or if something is not connected that should be, or if inverters can confuse TRMS meters (although I don't think so), or what is going on here. Anyone have any ideas they can share? Thanks!
ETA: I got off the phone with Wen. They were... yeah. Unhelpful. I could tell their expertise was in getting the engine started and that's about it. Any hard technicals about output are will beyond their scope. Sigh.