I think the indoor unit uses an AC motor on some of these M/S systems. My Sanyo uses a DC 280 volts, 47W brushless in the indoor fan. At least that's what the label says on the replacement motor.

But the two motors in the outdoor unit (fan & compressor) have their own DC controllers.
I think they might work like the brushless motors used in RC airplanes. (but don't quote me on that)! https://youtu.be/bCEiOnuODac
Anyways, both motors use feed-back from some type of speed (RPM) sensors to control their speeds, and the main-board CPU sets those speeds based on feed-back signals from the outdoor & indoor unit temperature sensors and the indoor thermostat.

In other words, it's not simple to run the hardware without some smart firmware.. :)
I would like to learn more about how these things work, but I've got way too much other stuff on my plate these days.

Cheers,
Rich

What he said...

A lot of the variable capacity mini-split systems have brushless DC motors inside the pot. Most have 3 phase stators and a permanent magnet rotor. The control systems are all somewhat proprietary, custom matched to a particular brand of compressor.

Most of the compressors work just like a front load washer or treadmill motor: high power DC is switched in and out of the circuit in a manner that makes the motor turn. Older models use some sort of rpm sensor for feedback, newer models monitor the motor current and back EMF to determine position and speed.

For a good read on this type of system, look up NXP document AN5387. It's for a refrigerator, but the strategy is the same. A lot of the newer mini-split compressors are double-stacked as well: 2 compression stages in one shell (Mr. Slim, hyper heat,etc.).

thanks for the new gizmo sir,

by the way is it available on EBay? or any online store? thanks in advance

The search terms might be too convoluted for Ebay..
This link Aliexpress is still okay.. https://www.aliexpress.com/item/32956162411.html

I know its not 100% related to the thread but did you spot any controller for air source water heater thta could be used for hydronic? I try to convert one (alredy a air source water heater) but the temp is limited since its a pool heater. My machine is not inverter technologie.