# Can A 50 Hz Motor Be Run On 60 Hz?



## T. J. (Oct 24, 2016)

I am looking at a Baldor 1/2 HP 3 phase motor, Catalog number M3538-50.  On the nameplate it is labeled 50 Hz and 1425 RPM.  Would it be safe to run this motor on 60 Hz?  I understand that it would run at 1725 RPM (which is what I want).  Most motor nameplates that I have seen specify that they can be wired for either frequency.

I just want to make sure that I can use this motor before I buy it.


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## RJSakowski (Oct 24, 2016)

I would expect a motor intended for 50 hz. operation, if anything, to be more efficient at 60 hz.


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## dieselshadow (Oct 24, 2016)

I wouldn't hesitate to run that motor as long as the voltage is correct. You are correct in thinking it will run faster. Frequency is speed in electrical terms.


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## markba633csi (Oct 24, 2016)

I think it will actually run at 1710 rpm :    6/5 = 1.2 x 1425 = 1710  feel free to check my math
MS


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## CluelessNewB (Oct 24, 2016)

I believe that is a* 3 phase* motor which is fine if that's what you are looking for.


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## T. J. (Oct 24, 2016)

CluelessNewB said:


> I believe that is a* 3 phase* motor which is fine if that's what you are looking for.


Yes, that is what I'm looking for.


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## Ulma Doctor (Oct 24, 2016)

you won't have any problem running the motor on 60 hz


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## T. J. (Oct 24, 2016)

Thanks for the replies. The motor is on its way and soon to be mounted on my Logan lathe.


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## Bob Korves (Oct 24, 2016)

http://elec-toolbox.com/Formulas/Motor/mtrform.htm 
A four pole 60hz motor will ideally run at 1800 rpm.  Under load, in real conditions, it is somewhat less.  You will see various numbers like 1710, 1725, and 1750 rpm on 4 pole 60hz motor data plates.  I think that motors are rated at some fairly high load, perhaps full rated load.  

Well, quality industrial rated domestically built motors anyway.  Cheap motors are rated using some Hocus Pocus method that makes them more than 100% efficient.  I have two 115v shop vacs with 15 amp plugs that both claim 5.5hp.  Sorry, that is impossible, unless smoke and mirrors are involved...


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## markba633csi (Oct 25, 2016)

946 watts = 1 horse at 100% efficiency right?


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## David S (Oct 25, 2016)

I think 746..just a typo

David


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## John Hasler (Oct 25, 2016)

Bob Korves said:


> I think that motors are rated at some fairly high load, perhaps full rated load.



As far as I know NEMA motors are rated at full load, which is the load at which they can run continuously.



> Well, quality industrial rated domestically built motors anyway. Cheap motors are rated using some Hocus Pocus method that makes them more than 100% efficient. I have two 115v shop vacs with 15 amp plugs that both claim 5.5hp. Sorry, that is impossible, unless smoke and mirrors are involved...



I think that is the peak power that the motor can put out for a few seconds.  A totally useless number, of course.


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## JimDawson (Oct 25, 2016)

John Hasler said:


> As far as I know NEMA motors are rated at full load, which is the load at which they can run continuously.  I think that is the peak power that the motor can put out for a few seconds.  A totally useless number, of course.



I think that number is something just dreamed up by the marketing department.  But most marketing types live in an alternate universe where our laws of physics don't apply.


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## John Hasler (Oct 25, 2016)

JimDawson said:


> I think that number is something just dreamed up by the marketing department.  But most marketing types live in an alternate universe where our laws of physics don't apply.


Oh, I suspect that you can get 5.5hp out of that motor for a few seconds.  It is a series motor, after all.  Run it up to max rpm no load, pop the clutch to the dynamometer, and watch the needle briefly touch 5.5hp.  Then the motor catches fire and the breaker trips.

[Edit] Also, to the people who sell these sorts of products rating of a motor is the power *input*.  On those machines all the air goes through the motor so it can be quite the hair dryer without melting.


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## Bob Korves (Oct 26, 2016)

John Hasler said:


> Oh, I suspect that you can get 5.5hp out of that motor for a few seconds.  It is a series motor, after all.  Run it up to max rpm no load, pop the clutch to the dynamometer, and watch the needle briefly touch 5.5hp.  Then the motor catches fire and the breaker trips.
> 
> [Edit] Also, to the people who sell these sorts of products rating of a motor is the power *input*.  On those machines all the air goes through the motor so it can be quite the hair dryer without melting.


Well, it can't really be input, either.  5.5 hp times 746 watts per hp divided by 115 v equals 35.7 amps.  The 115v supply will trip long before that.  Marketing hype and not being held accountable are no doubt the main reasons.


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## John Hasler (Oct 26, 2016)

Bob Korves said:


> Well, it can't really be input, either.  5.5 hp times 746 watts per hp divided by 115 v equals 35.7 amps.  The 115v supply will trip long before that.  Marketing hype and not being held accountable are no doubt the main reasons.


The rated current of a circuit breaker is the current that it will carry without ever tripping.  It won't trip instantly above that: you'd never start a motor.  There is a time delay that decreases as the overcurrent increases. The instant trip current can be many times the rated current.

http://static.schneider-electric.us...100-400 A Frame FA-LA/FA-FC-FH/0600DB0105.pdf


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## Bob Korves (Oct 26, 2016)

John Hasler said:


> The rated current of a circuit breaker is the current that it will carry without ever tripping.  It won't trip instantly above that: you'd never start a motor.  There is a time delay that decreases as the overcurrent increases. The instant trip current can be many times the rated current.
> 
> http://static.schneider-electric.us/docs/Circuit Protection/Molded Case Circuit Breakers/0100-400 A Frame FA-LA/FA-FC-FH/0600DB0105.pdf


I see, John.  Thanks.  The break times listed in your link are much longer than I anticipated at overload.  Of course, even giving a rating that a motor might sustain for a minute or so until the breaker opens or the motor or wiring melts is not at all being honest with the customer.  There was a time when ratings were conservative, and a motor would be rated at a value that it could sustain indefinitely, and with a generous reserve for less than perfect conditions.  Some are still rated with that mindset, and have good reputations.


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## John Hasler (Oct 26, 2016)

Bob Korves said:


> I see, John.  Thanks.  The break times listed in your link are much longer than I anticipated at overload.  Of course, even giving a rating that a motor might sustain for a minute or so until the breaker opens or the motor or wiring melts is not at all being honest with the customer.  There was a time when ratings were conservative, and a motor would be rated at a value that it could sustain indefinitely, and with a generous reserve for less than perfect conditions.  Some are still rated with that mindset, and have good reputations.


I agree that the 5.5hp rating is ridiculous but on the other hand  continuous-duty ratings for many applications would not be very useful.  You don't really want to know how much power your electric drill could reliably deliver running 24 hours a day.  You want to know what peak power it can deliver for long enough to drill a hole.


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## mzayd3 (Oct 26, 2016)

It will be fine so long as the volt : hertz ratio is consistent. Otherwise, motor life might shortened a little bit. It should be fine.


Sent from my iPad using Tapatalk


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## 4GSR (Oct 26, 2016)

Remember all of the old Craftsman power tools that were rated at peak horse power?  Some more smoke & mirrors tricks Sears marketing used.


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## Tony Wells (Oct 26, 2016)

I was about to mention that. Lawsuits finally shut that nonsense down. But it took a while, so there are many mis-marked motors out there.


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## bfd (Oct 27, 2016)

I asked that same question to our motor (electrical) engineer at work but it pertained to a welder gen Lincoln from  Europe  and I asked if I ran the engine at 3600 rpm would I get 60 hz out of it instead of the rated 50 hz, he said yes that would do it but if I ran it at that increased  speed I may cause the rotor to come apart. so to make a long story longer I did and it didn't but then the engine stopped working and I didn't need it so it sits and rusts bill


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## 4GSR (Oct 27, 2016)

A place I worked at in the late 1970's bought a No. 5 Milwaukee vertical mill that came out of Western Germany.  Besides the mill being all metric, it had a 50 HP motor that ran the spindle.  This motor was a 380V 50 Cycle 3 Phase motor.  Boss was too cheap the change out that motor for something more realistic that would run on 460V 60 cycle.  They hooked it up on 480V 60 cycle.  It ran, but ran hot.  Motor didn't run continious, so I guess that helped.  It was still running when I left there a couple years later.


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## John Hasler (Oct 27, 2016)

4gsr said:


> A place I worked at in the late 1970's bought a No. 5 Milwaukee vertical mill that came out of Western Germany.  Besides the mill being all metric, it had a 50 HP motor that ran the spindle.  This motor was a 380V 50 Cycle 3 Phase motor.  Boss was too cheap the change out that motor for something more realistic that would run on 460V 60 cycle.  They hooked it up on 480V 60 cycle.  It ran, but ran hot.  Motor didn't run continious, so I guess that helped.  It was still running when I left there a couple years later.


The tolerance for 380VAC 50Hz was +10-6% so that motor should have been good for 418VAC at 50 Hz.  The V/Hz ratio for 380VAC 50Hz is 7.6.  Adding 76 volts we get 494VAC at 60Hz for that motor.  Should be fine at 480VAC 60Hz as long as the insulation can stand it (not likely that it can't) and torque is reduced to 80% or less of rated to stay at rated power.  Of course, it is also unlikely that your nominal 480 was actually 480 at the motor.


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