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jeff5may · 09-03-19, 08:07 PM

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.).

09-03-19, 08:07 PM	#22
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	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.). Last edited by jeff5may; 09-03-19 at 08:55 PM..