VFD Explained: How a Variable Frequency Drive Works

What the video shows

How a variable frequency drive works: rectifier, DC bus and IGBT inverter, PWM, control modes, energy savings, braking and harmonics, in 5:52. An induction motor's speed follows the supply frequency (n = 120·f/p; a 4-pole motor turns at 1,500 rpm on 50 Hz). Inside a VFD are a rectifier, the DC bus (around 560 V DC on a 400 V supply) and an IGBT inverter that builds a new three-phase output with PWM. The video covers V/f, sensorless vector and closed-loop vector control, the cube law on pumps and fans (about 51 % power at 80 % speed), braking and regeneration (ramp, braking resistor, active front end), harmonics and practical installation tips.