60Hz US Motor in UK
60Hz US Motor in UK
(OP)
I have a compressor fitted with a 230v 60Hz single phase cap-start, cap-run motor. It is meant to run at 3450 rpm. Although it will run here in UK on 50Hz, after a couple of minutes the caps begin to smoke! I think that the reduction in operating frequency means that the motor does not reach sufficient speed for the centrifugal switch to cut out the start side. Apart from replacing the motor, is there anyway to solve this ?





RE: 60Hz US Motor in UK
RE: 60Hz US Motor in UK
Mark Empson
http://www.lmphotonics.com
RE: 60Hz US Motor in UK
Make sure to tell us if this works!
RE: 60Hz US Motor in UK
RE: 60Hz US Motor in UK
50Hz motors are physically larger than their 60Hz counterparts. They need more iron.
Mark Empson
http://www.lmphotonics.com
RE: 60Hz US Motor in UK
RE: 60Hz US Motor in UK
Good luck.
Mark Empson
http://www.lmphotonics.com
RE: 60Hz US Motor in UK
RE: 60Hz US Motor in UK
Xc=1/(2 x pi x f x C)
RE: 60Hz US Motor in UK
Take the core of a transformer 1/3 the size of the motor and make enough turns with the same wire size as the motor has. The goal is to keep the factor voltage/frequency (V/F) constant.
You still need to deal with that centrifugal switch but the motor will not burn out.
Good luck! :)
RE: 60Hz US Motor in UK
RE: 60Hz US Motor in UK
The problems that I see are:
1. The reduced frequency with the same voltge will increase the flux in the iron and probably cause the motor to fail due to increased iron loss. see http://www.lmphotonics.com/faq.htm#60_50
2. The centrifugal switch not operating due to lower speed.
3. Starting capacitor.
1. The flux in the iron should be kept at the design flux which will require that either you reduce the supply voltage by the same ratio as the frequency reduction, or you rewind the stator with more turns.
2. The switch can be modofied by altering the springs to operate at a lower speed.
3. The start capacitor may need to be increased in value to give the same phase shift. I suspect that you will get away with it though.
Adding capacitors across the windings will reduce the current from the suplly and will apear to be improving the situation, but this is just power factor correcting the motor and does not affect the flux in the iron so it will have no bearing on the shortened motor life.
If the motor has been wound to operate on both 50 and 60Hz, then you have no problem.
I have personally experienced a motor on a coolant pump that lasted about 6 weeks between failures. This motor was amnufactured in the USA and was stamped 230V 50Hz on the name plate. After the third failure, we came to the conclusion that rather than wind for 50Hz, then manufacturer had just change the name plate. We then altered the stator turns to accommodate the change in frequency and the motor operated faultlessly for 15 years until the machine was retired.
Mark Empson
http://www.lmphotonics.com
RE: 60Hz US Motor in UK
RE: 60Hz US Motor in UK