Just noticed strange behavior on my old Kill-a-Watt P3 plugged into BESTEK 1200W PWS inverter...
With no load plugged in to Kill-a-Watt
* Hz reporting as 13.5 (not 60)!
* Volts read higher than inverter's display... about 123 volts vs 115 on the inverter.
* slight flickering of the Kill-a-Watt display
Plugged in a lamp with 100W incandescent bulb -- purely resistive load. Kill-a-Watt reports
* Hz, still 13.5 (not 60)
* Volts even higher than 130 Volts
* Power reading 95 watts (close enough)
Lamp plugged into house power with the Kill-a-Watt looks perfectly normal. No flicker in the display either.
Why?
I'm still shopping oscilloscopes, so I can't see phase shifts or waveform distortions. It's a very old Kill-a-Watt meter, but it seems to output correct numbers as long as it's plugged into the grid power. It just doesn't play well with my inverter. Yes, I know, it's a cheapie inverter. But it is pure sine wave. And, it's 1200W output rating is much larger than even the 100 W lamp plugged into it. So I'm not pushing the limits of the inverter where I'd expect to see some funny numbers.
Is anyone else having this problem?
Seems like many people rely on the Kill-a-Watt numbers when testing inverter based solar systems (HoboTech comes to mind). But if noise, distortion and reactance are skewing the Kill-a_Watt readings, how can I trust it for measuring loads on my DIY system?
UPDATE:
I just so happen to have an older BESTEK 1000W PSW inverter. It looks identical to the new 1200W version. I checked the same numbers on this inverter and they look normal. So I'm speculating that the 1200W is malfunctioning, despite being able to power loads.
With no load plugged in to Kill-a-Watt
* Hz reporting as 13.5 (not 60)!
* Volts read higher than inverter's display... about 123 volts vs 115 on the inverter.
* slight flickering of the Kill-a-Watt display
Plugged in a lamp with 100W incandescent bulb -- purely resistive load. Kill-a-Watt reports
* Hz, still 13.5 (not 60)
* Volts even higher than 130 Volts
* Power reading 95 watts (close enough)
Lamp plugged into house power with the Kill-a-Watt looks perfectly normal. No flicker in the display either.
Why?
I'm still shopping oscilloscopes, so I can't see phase shifts or waveform distortions. It's a very old Kill-a-Watt meter, but it seems to output correct numbers as long as it's plugged into the grid power. It just doesn't play well with my inverter. Yes, I know, it's a cheapie inverter. But it is pure sine wave. And, it's 1200W output rating is much larger than even the 100 W lamp plugged into it. So I'm not pushing the limits of the inverter where I'd expect to see some funny numbers.
Is anyone else having this problem?
Seems like many people rely on the Kill-a-Watt numbers when testing inverter based solar systems (HoboTech comes to mind). But if noise, distortion and reactance are skewing the Kill-a_Watt readings, how can I trust it for measuring loads on my DIY system?
UPDATE:
I just so happen to have an older BESTEK 1000W PSW inverter. It looks identical to the new 1200W version. I checked the same numbers on this inverter and they look normal. So I'm speculating that the 1200W is malfunctioning, despite being able to power loads.