Page 121 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Capacitor start capacitor run motor (Fig 6)

It is the only single phase motor which has high starting torque and high power factor from no load to full load. In
this motor there are two condensers connected in parallel to each other but series with starting winding.
At the time of starting the starting condenser remains in the circuit which is three times higher in value than
running condenser. After the motor has achieved its normal speed thwarting condenser is cut off from the circuit
by centrifugal switch and thus only running condenser is left in the circuit which is comparatively of low value.
Application
It is used for operating compressors of air conditioner and big water coolers etc.
Permanent capacitor motor

In this case there is no centrifugal switch the starting winding is connected in series with the capacitor. This
capacitor remains permanently in series even in running condition `this motor has very low starting torque which
is only 50 % of the full load torque. This type motor is only used in ceiling fans, and where low torque is needed.

Shaded pole motor
It is a single phase induction motor provided with the auxiliary short circuited winding. This short circuited winding
termed as shading coil consists of a low resistance ring embedded on one side of each stator pole and is used
to provide the necessary torque. A shaded pole motor has a squirrel cage rotor and salient poles on which main
pole winding is done. In addition to the main pole winding on the salient poles, a short circuited low resistance
copper ring is also put to enclose about 1/3rd of pole shoe. This short circuited copper ring is known as shading
ring and acts as another winding.

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CITS : Power - Electrician & Wireman - Lesson 70-75