Speed control of three phase induction motor based on V/F

Controlling the speed of a three-phase induction motor using V/F (Volts per Hertz) is a widely used and reliable method

What is V/F Control?

V/F control maintains a constant ratio between supply voltage (V) and frequency (f) to:

• Keep air-gap flux constant
• Avoid saturation at low frequencies
• Ensure stable torque across the speed range

This method is scalar control (not vector), suitable for systems not requiring fast dynamic response or precise torque control.

How V/F Control Works

1. Set speed reference
2. Convert reference speed into a desired supply frequency
3. Calculate corresponding voltage to maintain constant V/F
4. Generate three-phase sinusoidal PWM signals
5. Drive the inverter to supply the motor
6. Measure actual speed and apply feedback (optional, for closed-loop)