General > General Technical Chat

🆘 Relay specifically tripping inverter!!! 🆘

(1/7) > >>

bigjoncoop:
I have spent over a week on this problem, pulling my hair out and finally narrowed it down to the relay itself....

ISSUE: trying to power a small air conditioner unit from inverter, but when using the factory relay that kicks on the compressor, it trips the inverter protection! IF I BYPASS THE RELAY AND HARD WIRE THE COMPRESSOR, THE INVERTER HAS NO PROBLEM RUNNING IT. (specific relay datasheet below)

Main Question: is there a simple solution to mitigate the spike of the relays contacts closing? Or should I remove the relay and try to use a mosfet instead?

(from searching online I found a couple possible solutions. Using either a Metal-oxide Varistor (Vos) or a TVS Diode. Your thoughts, would these work?)



More Info: the air conditioner main board has a time delay to engage the compressor. Originally every time the compressor kicked on it was tripping my inverter. So I went down a week's long rabbit hole trying to implement a couple different soft starter methods. I've tried using NTC inrush current limiters, as well as making a resistive inrush current limiter with a on time delay circuit and I had some varying success...

So I then decided to just completely bypass control board and to my surprise with no inrush current limiting whatsoever, the inverter has no problem powering the air conditioner with the fans and compressor kicking on at the same time.

So I now narrowed it down to the relay for the compressor is what is tripping the inverter! It would be ideal to be able to still use the factory main board in the air conditioner since it provides all the float switch sensors and the delay for the compressor etc.. If I can't figure out the relay problem I'm just going to hardwire the whole damn thing but I'd rather not

Any ideas on how to avoid this? Is there a way to smooth the spike of the relay contacts or should I maybe try to remove the relay and install a mosfet instead?

edpalmer42:
A MOV or TVS Diode is unlikely to solve your problem or if it does solve your problem, it's solving the wrong problem!

How old is the air conditioner?

Since bypassing the relay works, your inverter is able to tolerate the inrush current from the compressor.  The relay's purpose isn't to limit inrush current, but to control when the compressor operates.  Isn't it the main control to turn the compressor on and off in response to the thermostat?  If you bypass it, aren't you disabling all temperature control?

My first thought is that the relay is either old and near failure or just cheaply built.  When the (perhaps burnt) contacts close, the arcs generated at the contacts send noise back into the inverter that shuts it down.  If you have a beefy powerline filter, maybe in a power bar, you could wire it between the air conditioner and the inverter and see if that helps.  Note that the filters in power bars are typically low end and might not be adequate.  And their 15 amp rating is marginal when considering the inrush current from an air conditioner.  A proper test would involve a standalone filter module rated for at least 20A.

Ultimately, I think the proper solution is to replace the relay - perhaps with a higher power unit.

Ed

bigjoncoop:
Hey @edpalmer42

Thanks for your reply.

The air conditioner is brand new. It's an LG portable air conditioner. I've only run it a few times for a couple minutes here and there trying to get this all to work.

I mentioned I could just bypass the relay and hardwire it because having temperature control / thermostat is not necessary for my application. But like I said I would rather not do that since I would loose the built-in safeties and controls.

So you think the culprit might be the relay itself though huh? That would be easy enough to diagnose. I will give that a shot this evening when I get home and report back. That would be very convenient if that's the problem 😜! Fingers crossed!

* also I was thinking that another easy solution could be to just use the current relay to trigger either a mosfet or SSR... I have a spare solid state relay that's rated high enough for a compressor.

Someone:
When you bypass and "hard wire" I assume that is while the inverter is off/isolated, if so then when you turn it on the inverter is likely "soft starting". A relay turning on/off will cause a hard transient load, compressors are notorious for tripping inverters or stalling generators as they can demand a huge startup current. Oversize the source inverter/generator or get a compressor with its own inverter drive circuit that soft starts.

Circlotron:
Could be that contact bounce on your relay is sending very rude signals back to the inverter. I'd try a SSR in line with the relay and switch the relay on first / off last.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod