Why we use a capacitor in an electric fan?

Why we use a capacitor in an electric fan?

Answer:

1. Capacitor is used for both starting the electric fan and improving power factor.

2. The voltage taken by the fan during running has lagging power factor and in order to run the fan we need leading power factor. The capacitor increases the power factor. So we use capacitor in fan to increase its power factor.

3. To give a quick start-up for any instrument, capacitor is used in electronics, by using capacitor in the start-up there is a charge accumulation in between the plates of capacitor,whichis discharged again and gives a quick start to the instrument otherwise we have to use a very high voltage to the instrument

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ANNA UNIVERSITY-2008 REGULATION-EEE SYLLABUS

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Construction details of synchronous generator

Construction details of synchronous generator

    Consists of two parts namely stator and rotor

Stator

•   Laminated core with slots to hold the armature conductors.
• Laminated construction keeps eddy current losses to be minimum
•   Made up of material like silicon steel to reduce hysteresis losses

Rotor

     Two types

1.       Salient pole type
2.       Non salient pole type

Salient pole type

Non-salient pole or Smooth cylindrical rotor

Difference between salient and cylindrical rotor

SI.NO	Salient pole type	Smooth Cylindrical type
1	Poles are projected out from surface	Poles are not projected
2	Large diameter, small axial length	Small diameter, large axial length
3	Air gap is non-uniform	Air gap is uniform
4	Mechanically weak	Robust
5	Preferred for low speed alternators	Preferred for high speed alternators
6	Prime movers used are water turbines, IC engines	Prime movers used are steam turbines, electric motors
7	Damper winding is provided	Damper winding is not necessary
8	For same size rating is smaller than cylindrical type	For same size rating is higher than salient pole type

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