About Inverter Compressor: Starting Current

[Anand Sivaram]

If we would like to go completely off-grid with a Solar inverter:

Normal refrigerators use induction motors for compressors and these induction motors do require around 5x starting current. So, if we use a refrigerator with rated power of 200W, we would require an inverter/power supply rating of minimum 1000W. Otherwise there is chance that the inverter/power supply could trip.

What about refrigerators using modern Inverter Compressors? What type of starting current do they take? What type of motors these Variable Frequency Drive based Inverter Compressors use - Induction or Synchronous AC motors?

 

[essenmein]

At a guess you'd think inverter based drive would have softstart functionality, ie lower inrush, as far as machine types go, I'd bet that its still using the very cheap to make induction machine.

 

[Windadct]

I am pretty sure that the fridge compressors are piston style, that is part of the issue, the compressor may need full torque at "zero" speed, or it may fail to start. An inverter based fridge MAY help, but all of the energy in this start then needs to be in the DC link - I doubt it was built to do this due to the cost.

Best bet is to ask the manufacturer for a start profile. If you explain your situation properly, and they are a customer focused company they should, eventually, get you the answer.

 

[Anand Sivaram]

I am pretty sure that the fridge compressors are piston style, that is part of the issue, the compressor may need full torque at "zero" speed, or it may fail to start. An inverter based fridge MAY help, but all of the energy in this start then needs to be in the DC link

It used to be a standard AC induction motor based on/off compressors, but nowadays many of the 5-star energy efficient refrigerators and ACs are using Inverter VFD compressors.

 

[Windadct]

Yes - but the starting torque, may still need a large amount of current - ran into this problem in residential AC, it can be done but it is difficult AKA expensive. The starting process, I believe was patented ( in that case).