Introduction motors part 2

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INDUCTION MOTOR A. Vania Politecnico di Milano, Dept. of Mechanical Engineering, Milan, Italy APPLIED MECHANICS – Prof. Andrea VANIA INDUCTION MOTORS 2 An induction or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor therefore does not require mechanical commutation, separate-excitation or self-excitation for all or part of the energy transferred from stator to rotor, as in universal, DC and large synchronous motors. An induction motor's rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used in industrial drives because they are rugged, reliable and economical. Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed service, induction motors are increasingly being used with Variable-Frequency Drives (VFDs) in variable-speed service. VFDs offer especially important energy savings opportunities for existing and prospective induction motors in variable-torque centrifugal fan, pump and compressor load applications. Squirrel cage induction motors are very widely used in both fixed-speed and VFD applications. APPLIED MECHANICS – Prof. Andrea VANIA ASYNCHRONOUS MOTOR 3 1 stator 2 rotor 3 motor shaft 4 air gap 5 rotor bars 6 rings APPLIED MECHANICS – Prof. Andrea VANIA PRINCIPLES OF OPERATION 4 The induction motor is an electrical motor that is composed of a stationary part, the stator, and a rotating part, the rotor. The rotor is rather massive. The stator contains a suitable even number of grouped windings (stator windings, stator poles). An alternate…