capacitor starting.docx

7/28/2019 CAPACITOR STARTING.docx

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CAPACITOR STARTING &

RUNNING OF INDUCTION

MOTOR

&

METHOD OF REVERSING THE

DIRECTION OF ROTATION


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AIM: effect of capacitor on the starting & running of the single phase induction motor and

method of reversing the direction of rotation.

Object: to find the need of a capacitor in auxiliary winding circuit of single phase induction

motor both in starting and running condition and to know how the reversal of direction of

rotation may be achieved.

Apparatus:

1. Single phase induction motor split phase type with capacitor in the auxiliary windings1 no.

2. Voltmeter 1 no.3. Ammeter 1 no.4. Single phase wattmeter 1 no.

Circuit diagram:

230V, 50HZ

A

V

WSTARTER WINDING

RUNING WINDING

MCB

Theory:

A single phase motor has auxiliary winding can be considered as equivalent to a 2 phase motor

having a single supply. But because that the two windings are not an identical i.e. impedance of

main and auxiliary windings are different, the two currents IM and IA will have a time phase

displacement. By any means the time phase displacement between the two currents , IM andIA

flowing through the two windings can be made 90 degree , a single phase motor will be behave

exactly like a two phase motor. The time phase displacement between IM and IA can be increased

by using the capacitor in the auxiliary windings. The capacitor will also improve the overall

power factor of the motor.

The direction of rotation of a split phase type induction motor having main and auxiliary of the

main windings, gets reversed if the current direction in the auxiliary windings is reversed. This is


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done by the reversing the two terminals connections of the auxiliary across the supply by using

the two ways switch.

Procedure:

1. Make the connections as per the circuit diagram.2. Switch on the supply and not the direction of oration of the motor.3. Remove the auxiliary winding connections by switching off the supply.4. Switch on the supply and note that rotor does not move.5. Give slight rotations to the rotor in a particular direction and note that the rotor picks

up speed in the direction.

6. Reconnect the auxiliary windings across the supply but without the capacitor wasconnected.

7. Allow the rotor to rotate and record voltmeter, ammeter, and wattmeter readings.8. Run the motor with auxiliary windings connected across the supply with the capacitor in

the circuit.

9. Hold the rotor by hand and then release the rotor and record the motor readings.10.Note the direction of rotations of the rotor.11.Interchange the terminal connection of the motors auxiliary windings across the supply.

Switch on the supply and note the direction of rotation of the rotor.

Observation table:

Sno. Power

input in

watts

Input

voltage in

volts

Input

current in

the

amperes

Direction of

roation

Without

capacitor in

the

auxiliary

windingsWith

capacitor in

the

auxiliary

windings

capacitor starting.docx

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