Motor used in ceiling fan:
Single phase induction motor is used for ceiling fan; this motor is more or less similar
to polyphase induction motor, except that
(i) its stator is provided with a single phase winding
(ii) Centrifugal switch is used in some types of motors in order to cut out a winding
used only for starting purposes; it has distributed stator winding and squirrel
cage rotor.
When single phase supply is fed, its stator winding produces a flux (or field) which is only
alternating i.e: one which alternates along one space axis only. It is not a synchronously
revolving (or rotating flux, as in the case of a two or three phase stator winding fed from 2 or
3 phase supply). Now, an alternating or pulsating flux acting on stationary squirrel cage rotor
can not produce rotation (only revolving flux can). Therefore, single phase is not self-starting.
To make single phase induction motor self starting the following method is adopted.
- Split phase motor.
- Capacitor start induction run motor.
Split phase motor:
Split Phase method: In this method, phase is split by introducing a resistance and a switch
in starting winding and both windings are connected in parallel with supply.
Capacitor – Start induction run motor:
The necessary phase difference between IS and Im is produced by connecting a capacitor in
series with starting winding. The capacitor is designed for short duty service. When motor
reaches about 75% of full speed, the centrifugal switch ‘S’ is open and cuts out both the
starting winding and capacitor from supply, thus leaving only running winding across the
line
gregorymasila answered the question on February 22, 2018 at 16:09
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