3 - Electric motors and power systems

Abstract

Electric motors are major users of electricity in industrial plants and commercial premises. Motive power accounts for almost half of the total electrical energy used in the UK and nearly two-thirds of industrial electricity use. Although many motor types currently in use (synchronous motors, PM synchronous motors, d.c. motors, d.c.-brushless motors, switched reluctance motors, stepping motors), most of the industrial drives are powered by three-phase induction motors. The majority of them are rated up to 300 kW The most efficient and flexible solutions to the energy saving problem are based on variable speed drives (VSDs). Using VSDs, the motor speed can be readily adapted to the requirements of particular applications. Generally, a power electronic system comprises two separate sets of circuits: the logic level control circuitry and the high power circuits. Recent developments in electronics made it possible to combine these two components into a single integrated circuit, the power integrated circuit (PIC). A PIC is defined as integrated circuit which combines the logic control and/or protection circuitry with power handling capability of supplying 1 A and withstanding at least 100 V.