Q. What is an AC drive?

Answer

AC Drive or alternative current drive is a type of electrical drive that is designed for precise control of AC motor speed. Controlling the motor speed is the primary function of AC drives. These are particularly used for three phase induction motors as such motors are predominantly used in a number of industries.Types and Features of AC Drives The most common types of AC Drives are: Induction AC Drive – this motor drive induces current into the rotor winding in the absence of any physical connection with the stator windings. This type of AD drive is adaptable to different environments and designed for considerable power and variable speed control. In induction motors, there is built-in mechanism to track loss of exact speed. Synchronous AC drive – this type of motor functions on constant speed to the maximum load. The rotor speed is equivalent to the speed of the stator’s rotating magnetic field. Reluctance and permanent magnet are two main types of synchronous motors and such motors are used where the exact speed of a drive should be sustained. Sensorless vector drives – these drives press into action autonomous control of both frequency and voltage supplied to the motor for optimum speed control. This type of AC drive is designed for low-speed torque output when coming near to DC motors. In this drive, sensorless denotes that no feedback sensor like a resolver or encoder is employed. Servo motor drives – this type is typically everlasting magnet synchronous motor which can be characterized by low torque-to-inertia ratio for increased acceleration ratings. The motor in this drive is controlled by instructions coming from a PLC (programmable logic controller). It performs feedback control by receiving signals from an encoder.