European motor tricks?

[jw62]

We have a couple of examples at our company of European OEMs who purposely wire motors for the lower voltage (277) and yet run them at the higher voltage (480). I have talked with a European tech who once told me that there was some trick like this that they did to get more power out of a motor. Does anyone here know the logic behind this?

Thanks

 

[Skogsgurra]

He told you half the truth.

This is sometimes being used when you have a VFD. By connecting for the lower nominal voltage and running them at a frequency that is 480/277 times nominal frequency and at 480 V, you get same torque at higher speed. And, presto! More power out of that motor.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ozmosis]

The function is used typically on motorised gearboxes that have a VFD. The output frequency would typically be set to 87Hz (where the supply frequency is 50Hz) and will allow you to use a smaller (cheaper) gearbox that has a higher ratio gear-train but resulting in the same output torque. It is a cost saving function that many OEM's have introduced (I know Bonfiglioli/Flender/SEW do this).

 

[aolalde]

Running a motor on higher frequency and proportional increased voltage, constant torque (approx. constant air-gap flux density) increases the core laminations magnetic losses and the friction and windage. The result is a reduced motor life expectancy due to increased stress, thermal on the insulation and mechanical on the bearings and rotor. But certainly the power output is increased due to the speed increase; HP= rpm*Torque/5252, (Torque in Ft-Lb)

 

[jw62]

Cool deal, thanks - this sounds familiar and makes sense. I went out and looked at the latest example of a motor that we have here that is wired like this - it's only running at around 48 Hz - so this may be an actual case of accidental miswiring or maybe just a bad calculation on how fast the machine would run in production.