Low amp soft starter recommendations?

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hry asked Aug 7, '22

Low amp soft starter recommendations?

Hello!

Like many others, I have a small fridge which is creating such a surge when the compressor kicks in that it hits the inverter (Phoenix 12/800) too hard.

The solution would be a soft-start module between the fridge and inverter. I am only finding these at around 16A current limitation. This would mean a peak wattage limit (~3500W) above what the fridge is creating anyway, and still higher than the peak the inverter can handle.

Is my reasoning correct?

Or, would a common 16A soft-start module do the trick anyway?

Or, can you recommend any low amp (by my maths, less than 6A) soft-start modules to keep the peak below inverter peak?

Thanks in advance!

H

Phoenix Inverter modifications peak

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Answer 1 · 2022-08-07T18:48:28Z

Mike Dorsett answered · Aug 07, 2022 at 06:48 PM

There are 3 options here:

1) Get a DC powered fridge - Danfoss make a 12/24V module that drives a small 3 phase compressor.

2) Get a larger inverter that can handle the peak power for the fridge - possibly use this only for the fridge.

3) Get a fridge with an inverter compressor. This will have low inrush current.

An 800W inverter I would regard as too small for running a fridge on, and small soft starters aren't common (as you have found) - and probably would not work as the compressor motor needs high torque to start. An attempt to soft start this would likely end up with a stalled motor, which would burn out.

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Answer 2 · 2022-08-07T20:08:40Z

Nev answered · Aug 07, 2022 at 08:08 PM

Copied from a previous post of mine:

________________

Surge currents can be a real issue and are apparently often much higher than anticipated.

Inverters vary enormously in their peak surge versus time capabilities.

A few years ago I had a 70l 100W rated "bar" fridge in our motorhome.

A quality 600W inverter could never start the compressor while a 800W would start it with some effort but it would stall about once a week requiring a restart. A 1200W inverter was neccessary for 100% reliability.

I experimented with several "soft start" devices and Googled circuitry with no improvement - ever. Others hopefully have more success. Try before you buy would be wise.

By contrast our much larger 255l Samsung fridge with a digital inverter compressor has now survived 8 years of fulltime travel powered by a dedicated 300W PSW inverter running 24/7.

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