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Eddy Current Drive For 20kw? Motor

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Some years ago I bought an extruder with an eddy current variable speed control fitted. However as I wanted maximum RPM from the motor I removed the Eddy drive complete and replaced it with a direct coupling with the motor on SD starting which has worked well. However Ive now striped the extruder down and will rebuild it.

My question is should I use the Eddy drive on another application and buy a replacement motor. Or should I consider the drive to be obsolete as Ive not seen any others on any other units that I have looked at.

Are Eddy drives efficient?



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Hi Terry

If you wish to vary the speed of the extruder, then the eddy current coupling is one means of doing this. One advantage of the eddy current coupling is that is essentially controls the torque so that transient loads are "torque limited". These were quite popular, but are not so popular any more due to the low cost of VFDs.


The eddy current drive has high slip losses when the speed is reduced and this results in lower efficiencies than can be achieved with a VFD. The slip losses are a function of the slip (difference in speed between the input and output) and the torque transferred from the input to the output.


Best regards,

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