Frequency of motor power supply 60 Hz versus 50 Hz

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Discussion Overview

The discussion centers around the implications of operating 60 Hz rated equipment on a 50 Hz power supply, specifically focusing on motor performance, potential modifications, and safety concerns. The scope includes technical explanations and practical considerations for industrial applications.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that a variable frequency drive (VFD) or thyristor might be a viable solution for running 60 Hz equipment on a 50 Hz supply.
  • Another participant notes that while a 60 Hz motor can operate on a 50 Hz supply, it will experience reduced efficiency, including a 20% drop in RPM and output power, along with increased core losses.
  • A later reply emphasizes that running a 50 Hz motor on a 60 Hz supply is generally safer than the reverse scenario.
  • Concerns are raised about the potential overheating and humming of motors not designed for reduced frequency operation, with a suggestion to check the motor's nameplate for voltage specifications for different frequencies.
  • One participant mentions the possibility of adjusting pulley diameter to maintain drum speed in an industrial application.
  • There is a reference to the differences in motor design, particularly regarding iron laminations needed for different frequencies.
  • A participant humorously notes the challenges of repairing modern appliances compared to older induction motors.

Areas of Agreement / Disagreement

Participants express varying opinions on the safety and performance implications of using 60 Hz motors on 50 Hz supplies, with some agreeing on the potential risks and others providing differing perspectives on motor design and operation. No consensus is reached on the best approach.

Contextual Notes

Participants mention the importance of checking motor specifications and the potential for overheating, but do not resolve the implications of different motor designs or the effectiveness of proposed solutions like VFDs.

rollingstein
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If a 60 Hz equipment needs to be run off a 50 Hz power supply (3 phase, AC) what are typical options?

One brute force approach is to simply change motors. But I was wondering if a VFD / thyristor or some such might work?

This is medium sized equipment with rating of ~5 kW.

As an aside, were someone to accidentally cross connect a 60 Hz rated motor to a 50 Hz supply would the results be disastrous? Is the risk symmetric? i.e. A 50 Hz motor connected to a 60 Hz supply?
 
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If you check the specs of the device, odds are it says it will run just fine on a 50hz supply, just at reduced performance.
 
Motor designed to 60 Hz will run on 50 Hz, but (as russ said, at reduced efficiency):
- reduced RPM (by 20%),
- reduced output power (by 20%, as it is function of RPM),
- reduced cooling (may be critical),
- inceased flux in core (increased losses, may be critical) -> can deal with it by reducing voltage.

It would be much safer to run 50 Hz motor on 60 Hz.

All in all.. it may be dangerous to motor. Some VFD is a good idea I think.
 
Thanks! 20% rpm drop we can probably tolerate. It goes into an industrial spin dryer.
 
I assume we're talking about an old fashioned induction motor, not one of these newfangled appliance motors that's driven by a microcomputer generating three phase... (Woe is me -- I can no longer fix wife's washing machine!)

Check nameplate of motor and see if it gives two different voltages for 50hz and 60 hz.
A 50 hz motor needs more iron laminations for same voltage than does a 60 hz motor. A high quality motor could be designed to run on either by simply including the extra iron. But one might want to adjust pulley diameter to restore drum speed.

If the motor is not suitable for reduced frequency it will hum and get very hot. As an old engineer from Tennessee put it, "If it'll fry spit it's in trouble". So give it the feel test after a few minutes of operation.

If it's "one of those newfangled ones" the computer is already a VFD that's probably oblivious to line frequency. But that's a guess from afar. I'm sure you can tell by looking at it.

"One experiment is worth a thousand expert opinions".
 

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