AC motors and adjustable speed drives-How to make a match

The author discusses factors to be considered in converting a fixed-speed motor application to adjustable-speed operation by means of solid-state adjustable-speed AC drives. Most often referred to as inverters, these drives use transistors or silicon-controlled rectifiers to change fixed-frequency to adjustable-frequency AC power. It is pointed out that by varying the output voltage and frequency of the incoming current in a precise ratio, these drives change the speed of an AC motor. With the advances in inverter technology and with the cost of AC drives falling, there are now affordable inverters available for almost any motor application, including those applications once limited to DC or hydraulic motors. Motor characteristics and load requirements are discussed