A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, micro drive, and inverter.

Frequency (or hertz) is directly related to the motor’s speed . In other words, the faster the frequency, the faster the RPMs go. If an application does not require an electric motor to run at full speed, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electric motor’s load. As the application’s motor speed requirements change, the VFD can simply turn up or down the motor speed to meet the speed requirement.


What are the Benefits of a Variable Frequency Drive?

  • Controlled Starting Current
  • Reduced Power Line Disturbances
  • Lower Power Demand on Start
  • Controlled Acceleration
  • Adjustable Operating Speed
  • Adjustable Torque Limit
  • Controlled Stopping
  • Energy Savings
  • Reverse Operation

A variable-frequency drive (VFD; also termed adjustable-frequency drive, “variable-voltage/variable-frequency (VVVF) drive”, variable speed drive, AC drive, micro drive or inverter drive) is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor

A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.

The VFD Panel (Variable Frequency drive panel) also known as VFD Control Panel are designed to control the speed of electric motor and feed pump. They are widely used in drilling, pumping and other large machine applications.

Types of Variable Frequency Drives

  • Eddy Current Drives
  • DC Drives
  • AC Drives

DC Motor Drives

DC motors have a rotating armature winding (winding in which a voltage is induced) but non-rotating armature magnetic field and a static field winding (winding that produce the main magnetic flux) or permanent magnet. Different connections of the field and armature winding provide different inherent speed/torque regulation characteristics. The speed of a DC motor can be controlled by changing the voltage applied to the armature or by changing the field current. The introduction of variable resistance in the armature circuit or field circuit allowed speed control. Modern DC motors are often controlled by power  electronics systems called DC drives.

Eddy Current Motor Drives

An eddy current drive consists of a fixed speed motor and an eddy current clutch. The clutch contains a fixed speed rotor and an variable speed rotor separated by a small air gap. A direct current in a field coil produces a magnetic field that determines the torque transmitted from the input to the output rotor. The controller provides closed loop speed regulation by varying the clutch current, allowing the clutch to transmit enough torque to operate at the desired speed. Speed feedback is provided by an integral AC tachometer.

AC Motor Drives

AC variable frequency drives are also known as, VSDs (variable speed drives), inverters, AFDs (adjustable speed drives), and micro drives. AC variable frequency drives are used in many applications such as AC Servo Systems, Air Compressors, Conveyor Systems, Lathes, Mills, Food Processing production lines, Waste Water treatment systems, Submersible Pumps, HVAC fans and blowers, and many more applications in the industrial manufacturing world.