Using 50hz [PSC] aircon compressor in 60hz grid

Discussion in 'General Electronics Chat' started by ednar, Mar 29, 2010.

  1. ednar

    Thread Starter New Member

    Mar 29, 2010
    One phase compressor. There is the overheating issue.

    What I noticed if after start I disconnect the start capacitor from the start winding the compressor sound getting quieter, I'm not sure it runs colder though (well possible since one winding is off).

    The question is if I reduce the capacitor value will it change anything or it just changes the phase, but still fully engages the start winding, I guess capacitor resistance is none so it is like a conductor just with the phase shift?

    The current value is 35μF I tried it with 15μF and it still started ok.

    Secondly the start winding resistance is 3.1 Ohm and the run winding 2.7 Ohm. If to interchange the windings and then use the start winding to run the compressor with the run winding disconnected from the capacitor will it help? Or the start winding has the wire too thin for that (but still it is constantly engaged as it is PSC so it maybe won't just burn).

    The compressor is Hitachi, some other brands like Toshiba are good for both 50 and 60 hz, not this one.
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    Increasing the frequency will reduce the current slightly, so the basic winding setup should be OK.

    I'd guess the actual problem is that the compressor is running 20% faster than intended, so the gas pressures (and hence compressor load) will have increased.

    You need an aircon engineer to adjust the gas volume in the system to bring the compressor discharge pressure back down, which should then allow it to run within specifications.
  3. ednar

    Thread Starter New Member

    Mar 29, 2010
    So even if the compressor is rated 50hz it can also run 60hz like double frequency rated compressors, but the gas pressure should be less if it runs on higher frequency (even as compressor is the same - the finished product will have different work pressure i.e. frequency dependent).

    I opened aircon which runs on 60hz, exactly the same setup, but with 2 times smaller capacitor even as power is only 1.4 times less.

    Does it make sense to reduce the capacitor value, so if it starts with 15μF to use it instead of 35μF with leaving PSC layout if it doesn't stall? Less torque means less heat? Also in a way if it runs faster - torque should be less?

    More generic question when motor designed for 50hz will be overheating when run on 60hz grid, I see some appliances even those with relatively powerful motor have dual 50/60hz rating, is it only the matter of ventilating properly or there are other factors in play.
    Last edited: Mar 29, 2010