ABSTRACT
There are two types of electric motors run from an ac power supply: induction motors (asynchronous motors) and synchronous motors. An induction motor possesses a shunt-type speed-torque characteristic when supplied at rated voltage and frequency. A synchronous motor has a constant speed characteristic at all loads. When a variable-frequency inverter feeds ac motors, variable speed–variable torque operation can be conveniently achieved. This chapter focuses on fundamental principles of inverter fed variable speed ac motors. Operation of both voltage-source inverters and current-source inverters to supply power to ac motors is described with necessary characteristic curves. A qualitative treatment on vector control is included.
