Is my inverter broken?

[atatistcheff]

I'm building a solar generator and using the GoWISE pure sine wave 1500W inverter here: https://www.amazon.com/gp/product/B01COA0UTE/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1.

Up to this point the inverter has performed flawlessly with resistive loads. I can run a 1500W heater pulling 120+ amps from the battery with no issues. I've run the 30 year old upright freezer in my garage for 8 hours. But now, I've tried to run a much newer (10-12 year old) refrigerator and the inverter keeps throwing a fault and turning off. My ammeters show the peak load is under 60A right before it faults. I can hear the compressor starting but I'm baffled to why it's failing when the current is half of what I've seen it do continuously. In my kill-a-watt tests the older freezer uses more kWh in a day than the refrigerator and the startup current is at least as high and probably higher (80A). Yet it can run the freezer just fine. So weird.

I hate to send this inverter back but I'm not sure what else to do.

 

[gnubie]

What make and model is the new fridge? Checking to see if its a 'throw the compressor across the mains' type or inverter type.

 

[Rider]

How long is the extension cord from the inverter to the fridge, and what gauge is it?

 

[svetz]

Possibly can't handle the in-rush current of the newer compressor during startup? If so you'd need a clamp meter that measures in-rush; possible you can calculate if from the LRA, but I don't know how.

Update: it could be the new refrigerator pulls lower in-rush, but does so for longer. Your inverter has a peak of 3000W, or 25 amps... so 60 or 80 is pretty high surge for it.

 

[atatistcheff]

Possibly can't handle the in-rush current of the newer compressor during startup? If so you'd need a clamp meter that measures in-rush; possible you can calculate if from the LRA, but I don't know how.

Update: it could be the new refrigerator pulls lower in-rush, but does so for longer. Your inverter has a peak of 3000W, or 25 amps... so 60 or 80 is pretty high surge for it.

The amperage I'm seeing is on the 12V side. So it's pulling less than 60A into the inverter which equates to maybe 800W. I can run my wife's hair dryer off this inverter pulling 132A and other than the 4ga wires warming up it has no problem at all.

 

[atatistcheff]

What make and model is the new fridge? Checking to see if its a 'throw the compressor across the mains' type or inverter type.

Maytag, can't seem to find the owner's manual but it's your typical bottom freezer model. Nothing fancy. Posting some photos.



I suppose it could be doing it so fast that the ammeter doesn't register in time before the inverter cuts out - maybe? But heck a 3000W inrush? That seems like it would throw my 20A house breaker.

 

[atatistcheff]

How long is the extension cord from the inverter to the fridge, and what gauge is it?

Tried a couple extension cords. Also straight into a Tripp Light power strip, same story. It runs for a while (idling I suppose) but when the compressor kicks in the inverter taps out.

 

[gnubie]

Household breakers don't instantly open as soon as their rating is exceeded unless its a gross overload. There's two tripping mechanisms, a thermal strip (time delay) and an electromagnet for quick trips in gross overloads. There is usually a letter on the breaker to indicate how quickly it trips for lower overloads.

 

[atatistcheff]

So I'm just wondering if it could be something other than load that's causing the inverter to fault? Since the power draw doesn't seem to be exceeding the inverter's capability, are there other reasons why an inverter would cause a fault? Reading the manual I just see three:

1. Too many watts
2. Over voltage - 16V
3. Under voltage - 10V

The voltage is about 13.2 and doesn't dip much at all thanks to the Sinopoly cells. So I think we can rule out the over/under voltage. The https://powertechon.com website is down since at least yesterday (which doesn't bode well for their 1 year guarantee). So I can't contact them to find out what else might be an issue. I'm starting to think there's something going on that the inverter just doesn't like such as a GFCI...

 

[gnubie]

It's possible the inverter is getting upset at the power factor of the compressor.

They don't tell you this anywhere in the inverters manual usually but the watt rating, if it's even true, is for a purely resistive load and needs to be derated taking the power factor of the load into consideration. That's why I was asking about the fridge being an inverter type or not.

Inverter types with active power factor correction (PFC) can be up around .95, while those without can be .8. A non-inverter fridge can be truly terrible, .6. If the capacitor intended for PFC (compensating for the motor's inductive nature) is too small for the motor, or just not present at all, you can get horrendous PF of .2.

Take your inverter's supposed rating of 1500 watts at face value then multiply it by the load's power factor and you get an idea of what might be going on. You won't necessarily see high current draws on the DC supply in these circumstances either.

 

[atatistcheff]

Yes, I'll bet it's something like that. Definitely not visible in the actual amp draw on the DC side. Bottom line is I probably can't fix it without buying a new fridge. Oh well, thanks for the info!

 

[gnubie]

There are so many factors at play that it can be really hard to work out what is really going on without taking a bucket of measurements.

For example,
Suppose we have a nice well behaved switching power supply rated at 2kW on its output and it is 100% efficient and it has a power factor of 1 because it uses a really amazing active PFC. We hook that up to an inverter with a continuous 2kW output. All good so far, 2kW in, 2kW out. 240v, 8 amps. Until we factor in the soft regulation of the typical direct HF inverter. When they are faced with a load their output voltage sags and then slowly climbs back up. Let's say that the output voltage sags to 120v. For a linear resistive load all that means is the current drawn by the device also halve, but we don't have a linear load we have a switching power supply it will react by doubling its current draw to compensate for the halving of the supply voltage. Still drawing 2kW but in a very different fashion. The inverter may be quite happy to supply 10 amps but now it has to supply 16 amps. *click*, the sense circuit detects > 10 amps and shutdown results, even though the overall power being drawn is still 2kW.

.. and that's just one scenario.

 

[efficientPV]

Is my inverter broken? Maybe, when did you try these other loads. I buy broken inverters off ebay like women buy shoes. I recently got one that worked when I plugged it in. I opened it up because you just have to look inside. I buy cause I'm bored and want something to fix. One of the boost converters had smoked. Used to be they fused each inverter section with a separate fuse. This had six 50A fuses in parallel. That amount of current just blows any short open. It still worked, it just could produce less power.

 

[b.james]

Would a soft starter work in this case?

 

[b.james]

I buy broken inverters off ebay like women buy shoes. I recently got one that worked when I plugged it in. I opened it up because you just have to look inside. I buy cause I'm bored and want something to fix.

I've got a few switching power supplies id like to get fixed . Where are you ?