Variable Frequency Drives

Typical AC Motors are designed to operate at a constant speed. A Variable Frequency Drive (VFD) is a piece of equipment that is able to modify the AC Frequency supplied to a motor. Where a standard motor is normally supplied with a 60 Hertz (Hz) frequency, the VFD is able to provide an AC frequency of 0 to 70 Hz, thereby changing the speed of the motor.

This is very useful in exactly matching the load for a given air handler, cooling tower or pump. So instead of operating equipment at full speed, fans can be slowed down at night, cooling towers can supply the optimal condenser water temperature and three way valves can be made obsolete through the use of a VFD.

How does a Variable Frequency Drive save energy?

“Savings from VFDs come from reduced load of the fan, pump, or driven device. With fans and pumps, power consumed is proportional to the cube root of shaft speed. If shaft speed is reduced by 10%, flow is reduced by 10%, while power consumption is reduced by 27%. If speed is reduced by 20%, power is reduced by 49%.”

* Source: Federal Energy Management Program - Washington State University

Additional benefits of a Variable Frequency Drive - since Variable Frequency Drives uses ramp up and ramp down times to limit the rate of speed change of the driven load, there is less wear and tear on belts, sheaves, bearings, pillow blocks and the fan itself. This can lead to reduced maintenance costs on associated equipment. Also due to the same soft start capability the typical loud squeal associated with speed changes is eliminated reducing ambient noise levels in the vicinity of the cooling towers or fans.

Corridor Fans
Cooling Towers
Pumps & Valve Controls