TYPES OF SINGLE PHASE MOTORS

Single phase motors are manufactured in fractional kilowatt range to be operated on single phase supply and for use in numerous applications like ceiling fans, refrigerators, food mixers, hair driers, portable drills, vacuum cleaners, washing machines, sewing machines, electric shavers, office machinery etc. Single phase motors are manufactured in different types to meet the requirements of various applications. Single phase motors are classified on the basis of their construction and starting methods employed. The main types of single phase motors are:
(a) Induction motors
(b) Synchronous motors
(c) Commutator motors

The various types of motors under each class are shown as under:

Repulsion, repulsion induction and reluctance start motors are not used these days, they have been largely replaced by split phase motors with special capacitors which can be designed to perform equally well as repulsion types. In addition they offer such advantages as lower cost and trouble free service.

Shaded pole motors are extremely popular motors used in low-starting torque applications. Split phase motors are widely used and are designed in several ways to develop different values of starting torque.

Universal series motor is another very popular type of motor which can operate on both ac and dc supply. They generally run at high speed and employ special design features to reduce commutation and armature reaction difficulties on ac supply.

Synchronous motors such as reluctance motor and hysteresis motor operate at synchronous speed for all values of load. They are manufactured in very small ratings. Practically all single phase motors are designed for line voltage starting and take inrush currents that may be little more than the rated values in some types and six or more times as much in others. Like polyphase motors they are also frequently jogged, plugged, reversed, dynamically braked and plug reversed. When the above mentioned operations are done, contactors of larger ratings than normal are used, as their frequent operations cause overheating and excessive wear of contacts. Control circuits of single phase motors are however simple as few contactors and relays are used.

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