In an AC compressor is 220/240@50 equal to 265@60? - Page 1
Forum section: electronics / beginners

author: Nightmare4u2c
author_rank: Contributor
timestamp: March 22, 2023, 08:19:50 pm
content: So looking to figure out how compressor output changes with Ac voltage and hertz changes. I understand the 50 to 60hz change will cause a 16.667% difference. Would like a explanation of how going from 240v/50hz to 265v/60hz is equal. As the attached photo shows. The AC compressor rating is 220/240 @ 50hz or 265 @60hz. I have contacted the AC manufacturer and was told it would run 17% faster and wear out prematurely if I were to run it on 240 @ 60hz unless I get the voltage up to 265. I did attempt to contact the compressor manufacturer but have yet to receive a response as to if it would cause premature wear. Just trying to understand how this works.

author: BillyO
author_rank: Super Contributor
timestamp: March 22, 2023, 11:02:00 pm
content: The motor is inductive so will appear to be a higher impedance to a higher frequency. So, in order to keep the current about the same, an increase in frequency will require an increase in voltage. The relationship depends entirely on the particular motor design.

author: Nightmare4u2c
author_rank: Contributor
timestamp: March 23, 2023, 10:08:38 pm
content: Thanks for the explanation. Still a bit over my head in technical speak but i do get the general idea. So obviously not knowing all the details of the compressor and going with common assumptions. What would the ramifications be if it were to operate at 240/60? Obviously it will run at 17% higher output and create additional heat. As long as the heat is kept in check there should be a minimal chance of premature failure. Or would the difference in hz create additional wear electrically that I'm missing?

author: johansen
author_rank: Super Contributor
timestamp: March 24, 2023, 02:00:02 am
content: this is a weird one.normally compressors are made for 240v 60hz which is the same as 200v 50hz, or they are made for 240v 50hz.this compressor you've found is sort of half way in-between. 265vac 60hz is 220vac 50hz, but we don't know if the amps for 50hz listed at 14, is for 220 or 240. or somewhere inbetween. if the manufacturer wants at least 265 then perhaps the motor was designed for 277vac 60hz, which would correlate to 230vac 50hz.in any case, once you have that compressor in circuit and your refrigerant system running at an average load.. what you want to do is add minimum 16 vac to your 240 v system and see if the compressor amps decrease. change that to adding 24v and see if it decreases still. add 32.. it will probably increase. 16/32v and 12/24v buck boost transformers are very common. you can also use a 40v:120v transformer in conjunction with a variac to sweep the voltage to find the lowest operating current into the motor.You also have to do this at just under the greatest load you expect the compressor to operate at. the reason why is because as the motor warms up and the refrigerant heats up, the load increases and so does the resistance of the motor. an optimal voltage at an average load is too low for high load.your compressor will run fine at 2/3rds the voltage on the nameplate if its an r-410 or r-32 compressor and you instead run it on propane, r-134A or r-1234yf. the lower pressure is a substantially lower load.

author: BillyO
author_rank: Super Contributor
timestamp: March 24, 2023, 08:34:17 pm
content: Quote from: Nightmare4u2c on March 23, 2023, 10:08:38 pmIf it's a universal motor, it will run slower and generate less heat. If it's an induction motor it will attempt to go 20% faster RPM, but it will have considerably less torque and might not be able to run properly at all with the load of the compressor.

author: Benta
author_rank: Super Contributor
timestamp: March 24, 2023, 09:18:11 pm
content: The problem with not running at a fixed V/f where the voltage is too low is increased slip.This will raise losses and thus temperature in both rotor and stator (and also in the bearings). I'd say the supplier feedback is correct.

author: johansen
author_rank: Super Contributor
timestamp: March 24, 2023, 10:15:38 pm
content: I am also concerned that the manufacturer does not list 2 different capacitor values for the different voltage and frequencies..

author: Benta
author_rank: Super Contributor
timestamp: March 24, 2023, 10:31:22 pm
content: Quote from: johansen on March 24, 2023, 10:15:38 pmNah, those are at least +/-20% tolerance. Makes no big difference.

author: johansen
author_rank: Super Contributor
timestamp: March 24, 2023, 11:50:01 pm
content: Quote from: Benta on March 24, 2023, 10:31:22 pmIt does when the motor takes twice as long to start, and burns out 50% sooner.

author: Benta
author_rank: Super Contributor
timestamp: March 25, 2023, 12:21:51 am
content: Quote from: johansen on March 24, 2023, 11:50:01 pmYes, exaggeration improves understanding and amplifies your argumentatation.I've said that a million times.