220v 50hz moto, no controls. hooked up 240v 60hz. will it be dammaged?

Status
Not open for further replies.
I don't think the voltage will be a problem, but the higher frequency (20% high!) might cause a problem.
 
220V 50Hz has a V/Hz ratio of 220/50 or 4.4:1 and at 240/60 the ratio is 4:1, so you will end up with 10% less flux which means 10% less torque. At the same time the speed is higher by 20%. So since HP = tq x RPM / 5252 and you have less torque but a lot more speed, you will end up with 11% more HP from the motor, but also more current because the slip will end up being higher as a result of lower torque. That means the motor will run hot. If, as is often the case, the motor was over sized in the first place by 10-20%, then you may not have a problem.

If the load is centrifugal however, then you may have another problem. In a centrifugal load like a pump or fan, your LOAD on the motor will increase at the CUBE of the speed difference. So that will be 1.23 or 173% of the original load! Even if the motor was over sized originally by 20%, you have 11% more HP but 53% more load, so you will overload that motor. Already hot + overload = failure. If you can restrict the flow in the pump or fan, that may fix the problem but if not, then it won't work.
 
Last edited:
the blur said:
I do it extensively with european equipment here in the usa, works fine. even at 208.
Click to expand...

That is likely because motors are oversized for the load. What Jraef described still happens, but you likely end up within the motors operating range is why you have no problem. You need to operate the load at both 50 and 60 hertz to see what the difference is.

There are motors that have dual frequency ratings on the nameplate. The corresponding voltage, current,speed, horsepower/wattage is also marked on the nameplate.
 
kwired said:
That is likely because motors are oversized for the load. What Jraef described still happens, but you likely end up within the motors operating range is why you have no problem. You need to operate the load at both 50 and 60 hertz to see what the difference is.

There are motors that have dual frequency ratings on the nameplate. The corresponding voltage, current,speed, horsepower/wattage is also marked on the nameplate.
Click to expand...

See this more and more all the time. The labels are getting very crowded and at times difficult to find what you want. Being an old guy with old eyes doesn't help.
 
Jraef said:
220V 50Hz has a V/Hz ratio of 220/50 or 4.4:1 and at 240/60 the ratio is 4:1, so you will end up with 10% less flux which means 10% less torque. At the same time the speed is higher by 20%. So since HP = tq x RPM / 5252 and you have less torque but a lot more speed, you will end up with 11% more HP from the motor, but also more current because the slip will end up being higher as a result of lower torque. That means the motor will run hot. If, as is often the case, the motor was over sized in the first place by 10-20%, then you may not have a problem.

If the load is centrifugal however, then you may have another problem. In a centrifugal load like a pump or fan, your LOAD on the motor will increase at the CUBE of the speed difference. So that will be 1.23 or 173% of the original load! Even if the motor was over sized originally by 20%, you have 11% more HP but 53% more load, so you will overload that motor. Already hot + overload = failure. If you can restrict the flow in the pump or fan, that may fix the problem but if not, then it won't work.
Click to expand...

Very good, explained response as usual. :happyyes:In general the pumps are way more oversized than motors, so he may be OK.
 
Status
Not open for further replies.
Top