Using Premium Efficiency Motors with VFDs on Your Dust Collector

There's some confusion as to why premium efficiency motors can be used with variable frequency drives (VFDs) whereas standard efficiency motors cannot. Camfil Farr APC technical director explains:

"One of the largest players in calculating the life expectancy or efficiency of an electrical motor is in its ability to dissipate heat or not generate heat in the first place. On standard efficiency motors, energy is lost in producing heat while another portion of energy is spent on the fan required to cool the motor. If you are not familiar with a motor design, there is a fan on the end of the motor. It is an integral part of the motor and is located on the opposite end of the output shaft. When the motor turns to perform the work you needed it for in the first place, it also turns the fan so that cooler air is blown across the motor itself. So, some of the energy you supply the motor to operate is used to turn the fan and not translated to the output shaft.

Premium efficiency motors reduce the amount of lost energy going into heat rather than power by using different and higher quality parts. Some of these parts include: steel with better magnetic qualities, bigger diameter wire, and better bearings. Since less heat is generated, less energy is needed to cool the motor with a fan.

Variable Frequency Drives (VFD’s) are used to speed or slow the operation of the motor. VFD’s can be used on standard efficiency motors, however it is not recommended or is very limited since standard efficiency motors do not have the same ability as a premium efficiency motor in limiting or dissipating heat caused by operation. Using premium efficiency motors in conjunction with VFD’s allows a much wider range to operate the motor while maintaining the expected motor life."