Why Use a Variable Frequency Drive?

The big question is why should I use a VFD (Variable Frequency Drive) or sometimes called a VSD (Variable Speed Drive). The answer is simple, when combined with a system variable, you can expect energy efficiency, as opposed to running a motor at full capacity although not required by the system. Not only can you expect energy savings, but also saving your equipment from the hard-starting action of a full inrush of current to the motor. Bearings, belts, fan blades, and gearboxes, lifespans will be greatly increased from the normal "snapping" of start and stop motions with your mechanical equipment.

There are many applications that are currently using VFD's: Cooling Towers, Compressors, Pumps, Fans, and any other piece of equipment that require variable load.

Justifying the Cost of Purchase

VFD's have come down in price over the years, due to higher production and cheaper electrical components. Over the last 10 years drives have become more efficient and reliable, and are becoming a key component in every mechanical room. Our sales staff can provide a ROI (return of investment) report to help justify the purchase of VFD. A nine times out of ten, you will have paid back the drive cost in less than 3 years of operation.


Hambrick-Ferguson Inc, can provide custom enclosed units as well as standard indoor/outdoor rated VFD's for Single Phase and Three Phase applications.

Shaft Grounding Devices

During variable speed usage through VFD's causes an induction of stray currents through the motor shafts of AC/DC motors. With the changing of frequency, we cause the stray eddy currents to seek the path of least resistance. Unfortunately that least resistance is through the bearings, out to the motor casing, and to ground. Pitting and fluting raceways in the bearing housing is the final result, causing eventual catastrophic bearing failure. With Shaft Grounding Rings, placed onto the motor shaft, the stray currents will take the path of the ring to ground to the casing rather than traveling through the bearings. This is the best preventative maintenance component, to reduce costly repairs and downtime of all your motors on VFD's. Just ask our Sales team about scheduling a "Shaft Voltage Test" on all your variable speed motors