SCR controls cost less than their PWM counterparts. This intuitively makes sense since the power section of a SCR control is a simply a rectifier bridge, while the PWM control has a diode bridge that costs roughly the same, plus the additional PWM components like BUS capacitors and MOSFETs or IGBTs.
A diode is an electrical component that allows electricity to flow in one direction, but not in the other. It’s similar to a check valve that lets water flow out, but not back in. It’s also like a flap on an exhaust vent. If air is flowing in the right direction, the force of the air opens the vent and allows the fumes to escape. Once the air stops blowing, gravity closes the flap to prevent the outside air, debris, fumes, or animals from getting back in.
An AC motor controller is known as the device that controls the speed of the AC motor. An AC controller can also be referred to as a variable frequency drive, adjustable speed drive, frequency converter and more. The AC motor receives power, which is converted by the AC motor controller into an adjustable frequency. This adjustable output allows the motor speed to be precisely controlled.