# Can a 60 hz motor run on 50 hz



## abdul

one another question related to motors is that: can a 60Hz motor work on 50Hz supply?


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## JRaef

abdul said:


> one another question related to motors is that: can a 60Hz motor work on 50Hz supply?


Maybe. It depends.
But you are hijacking someone else' thread.


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## TOOL_5150

JRaef said:


> Maybe. It depends.
> But you are hijacking someone else' thread.


looks like a brandy-new thread to me.


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## Dennis Alwon

I started a new thread for this question

A 60 hz motor on a 50 hz supply will usually slow down the motor by 20% slower . This may do some harm to the motor in he long run but there are other factors involved in this.


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## TOOL_5150

if the motor can run on 50hz, it will be posted on the nameplate. thats all there is to it.


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## tkb

Dennis Alwon said:


> I started a new thread for this question
> 
> A 60 hz motor on a 50 hz supply will usually slow down the motor by 20% slower . This may do some harm to the motor in he long run but there are other factors involved in this.


Will it harm it more than running the motor on a VFD at 50hz?
Would you have the same problem with bearings like on a VFD at one speed for a long time?


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## Dennis Alwon

tkb said:


> Will it harm it more than running the motor on a VFD at 50hz?
> Would you have the same problem with bearings like on a VFD at one speed for a long time?


I don't know. I assume that certain motors are designed to work at variable frequencies. 

Here is something I found.




> Using a 60Hz motor in 50Hz duty.
> w) It will turn 20% slower.
> x) Cooling will drop dramatically.
> y) The load's horsepower requirements will drop, possibly dramatically.
> z) V/f will increase possibly causing a large increase in current draw.
> 
> Make sure the load will still do what is required of it when running slower. For instance, a fan load would now move less air. Still enough?
> 
> The cooling will reduce dramatically. Is it enough to matter? This depends on how the load has decreased. If the hp requirement dropped because the load has decreased the current will drop and less heat will be released internally. You would want to take temperature measurements until the motor reaches a steady state temperature running in its new frequency application.
> 
> The motor's hp will drop because hp is a function of speed x torque. The motor's torque doesn't change but its speed has dropped so it is now a lower hp motor. If you change pulley sizes to return the load to its original speed your motor will likely be undersized, possibly seriously. Example: A 10 hp motor is now an 8 hp.
> 
> The most serious issue is the V/f issue. The V/f will increase. Likely enough to cause a large increase in the motor's current. This coupled with the reduced cooling may cause rapid overheating. However the V/f problem can be fully mitigated! You reduce the voltage to the motor by the amount required to return the V/f back to its original value. This removes the hazard of excess current from an increased V/f.
> 
> Example: A 60Hz 240Vac motor is going into 50Hz service.
> V/f = Y Hence: 240/60 = 4.0
> 
> So if Y x f = V then by plugging in the new frequency of 50 we see:
> 4.0 x 50 = V
> V = 200
> Running the motor at 200V at 50Hz will remove the V/f problem.
> 
> Another way to think of this is:
> New voltage = Old voltage x 50/60
> New speed = Old speed x 50/60
> New Horsepower = Old horsepower x 50/60
> Note: This would instead be 60/50 for a 50 to 60 Hz conversion.


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## micromind

Service factor would come into play here too. 

A motor with a SF of 1.15 or higher would stand a far better chance of running successfully on reduced frequency than one with a SF of 1.00


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## JRaef

This is why I said "It depends".

To have the same TORQUE from an AC motor, you have to maintain the same relationship between voltage and frequency, the "V/Hz ratio", within 10% of the motor design. If you don't do that, you either saturate the motor and over heat it or you under excite it and the loss of torque increases the slip, running a risk of overload. 

But check this out: a motor designed for 460V/60Hz has a V/Hz ratio of 460/60 or 7.67:1 and 380V/50Hz supply has a V/Hz ratio of 380/50 or 7.6:1! Hey, whadaya know! So if you are looking at that voltage class, the motor will be fine, it will just run slower (5/6 speed). Because HP (or Mechanical kW) is a function of speed and torque, even though the torque is the same, the speed drops so the HP drops proportionately. If the load needs HP, then you have to over size the motor, but if it needs torque, you are fine. So a load like a centrifugal pump or fan will run fine, just with lower output because of the loss of speed. that however may affect head pressure which may interfere with proper flow. 

If however you are using 230V 50Hz and the motor is designed for 230V 60Hz, the V/Hz ratio will end up out of tolerance. So in this case going from a 60Hz design to a 50Hz supply, the motor will not only spin slower, but it will produce significantly less torque. If it is again a centrifugal load that might be OK because the drop in speed will result in a drop in flow and thus motor load. But that still has the other risks and any other type of load will not likely work for long.


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## micromind

JRaef said:


> But check this out: a motor designed for 460V/60Hz has a V/Hz ratio of 460/60 or 7.67:1 and 380V/50Hz supply has a V/Hz ratio of 380/50 or 7.6:1!


This is why most motors that are rated for both 60 and 50HZ will list the 60HZ voltage as 230/460 and the 50HZ voltage as 190/380, even though a lot of 50HZ systems are 240/415.


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