Finding an inverter-friendly refrigerator? (Variable speed compressor one?) - Page 1
Forum section: electronics / projects

author: Freesurfer
author_rank: Regular Contributor
timestamp: June 23, 2019, 11:56:48 pm
content: I am trying to find a refrigerator that will run nicely on a 230V DC-AC inverter. That is, a fridge that doesn't have a huge inrush current whenever the compressor powers up.When looking around it has come to my attention that many new fridges aren't simple thermostat controlled on/off fridges, but use an inverter controlled compressor which can run the motor at the desired speed. They are more efficient, quieter, and most importantly in my case they don't have the problem with huge inrush current of starting the compressor directly from the mains.But when looking for an "DC-AC inverter friendly fridge", I cannot really tell from the description if they have this variable speed feature or not. I can only find expensive, large Samsung or LG fridges that actually boast or market their fridges as inverter controlled. So how can I tell? Can I assume that if the manufacturer doesn't actively boast about the inverter technology, chances are they don't have one? A seller in a local shop suggested a Matsui fridge, but I am very unsure whether or not it is actually an inverter fridge as it says it has a mechanical thermostat and there is no mention of a "variable speed compressor" or "digital inverter technology" anywhere.Examples of other fridge brands that are available in my region are AEG, Bosch, Electrolux, Gorenje, Gram, Liebherr, Logik, Matsui.So does anyone have a clue of where I should be looking?

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 23, 2019, 11:58:25 pm
content: Quote from: Freesurfer on June 23, 2019, 11:56:48 pmsee whats used in an RV or boat? Applications that use inverters and have fridges...

author: Freesurfer
author_rank: Regular Contributor
timestamp: June 24, 2019, 12:03:57 am
content: Thanks for your replay. I have looked at such places, but most of those fridges are very expensive (up to 3 times the cost of household fridges) and are usually absorption fridges designed for 12/230/LPG gas. So while they have the convenience of being capable of running on gas, they are less efficient than a compressor fridge when running on electricity. Also, I can mention that my battery bank is 48V, so a 12V fridge is unfortunately not an option in my case as that will unbalance the charge of the battery bank.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 24, 2019, 03:32:34 am
content: A special 2 phase inverter running a regular compressor would be a good solution, but I'm not aware of any such inverters available off the shelf. Just doing a V/Hz ramp up with a single phase inverter (as some high end ones already do for startup) would probably be good enough. Adding a "hard start kit" would help as well.As for the cheapest way that doesn't require too much in the way of custom electronics, start with a sine inverter board that accepts an analog input for V/Hz control. Connect that to a control circuit to take care of the ramping up/down as well as PID control. 30Hz would be a good lower bound on control range after ramp up, as in the ramp up itself should take less than a second. (As in on starting, ramp up from 0Hz to 30Hz in one second or less, afterwards vary the frequency anywhere within 30Hz and 50Hz with a reasonable slew rate as needed to regulate temperature.)