Variable Frequency Drive (VFD) Installation

Variable frequency drive

Cooper Electric installs and retrofits variable frequency drives for commercial and industrial facilities across Greater Cincinnati, helping you integrate today’s motor control technology into the trusted equipment you already rely on.

What Is a Variable Frequency Drive?

A variable frequency drive (VFD) controls the speed of an AC electric motor by controlling the frequency of the power supplied to it. VFDs are a type of adjustable-speed drive and are also called adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, microdrives or inverter drives. Because voltage is varied along with frequency, they are sometimes called VVVF (variable voltage, variable frequency) drives.

How a VFD Starts a Motor

A VFD starts a motor at a low frequency and voltage, typically 2 Hz or less. That avoids the high inrush current of starting a motor across the line. The drive then ramps frequency and voltage up at a controlled rate to accelerate the load without drawing excessive current.

This typically lets a motor develop 150% of its rated torque while the drive draws less than 50% of its rated current at low speed, and a VFD can be set to produce a steady 150% starting torque from standstill up to full speed.

Why Install a VFD?

• Soft starting that reduces inrush current and mechanical stress
• Precise speed control matched to the process
• Often a lower-cost alternative to an across-the-line starter
• Can add speed control to existing motors and machinery

VFDs create harmonic currents, so if your facility has power factor correction capacitors, see our power factor correction guidance on measuring harmonics. Explore our PLC and motor control services.