## EE6352 EEI Notes

Anna University Regulation 2013 ECE EE6352 EEI Notes for all 5 units and ECE 3rd SEM EE6352 Electrical Engineering and Instrumentation Lecture Notes are listed down for students to make perfect utilization and score maximum marks with our study materials.

### INDUCTION MOTORS

1. What are the 2 types of 3phase induction motor?

Squirrel cage and slip ring induction motor.

2. Write two extra features of slip ring induction motor?

Rotor has 3-phase winding. Extra resistance can be added in rotor circuit for improving PF with the help of three slip rings.

3. Why an induction motor is called as rotating transformer?

The rotor receives same electrical power in exactly the same way as the secondary of a two winding transformer receiving its power from primary. That is why induction motor is called as rotating transformer.

4. Why an induction motor never runs at its synchronous speed?

If the motor runs at sync. speed then there would be no relative speed between the two, hence no rotor emf, so no rotor current, then no rotor torque to maintain rotation.

5. What are slip rings?

The slip rings are made of copper alloys and are fixed around the shaft insulating it. Through these slip rings and brushes rotor winding can be connected to external circuit.

6. What are the advantages of cage motor?

Since the rotor has low resistance, the copper loss is low and efficiency is very high. On account of simple construction of rotor it is mechanically robust, initial cost is less, maintenance cost is less, simple starting arrangement.

7. Give the condition for maximum torque for 3phase induction motor, when it is running?

The rotor resistance and reactance should be same for max.torque i.e. R2=Sx2

8. List out the method for speed control of 3phase cage type induction motor?

By changing supply frequency By changing no of poles By operating the two motors in cascade

9. Name the two winding of single phase induction motor?

Running and starting winding.

10. What are methods available for making single phase induction motor a self starting?

By slitting the single phase, by providing shading coil in the poles.

11. What is the function of capacitor in single phase induction motor?

To make phase difference between starting and running winding, to improve PF and to get more torque.

12. State any 4 use of single phase induction motor?

Fans, wet grinders, vacuum cleaner, small pumps, compressors, drills.

13. What kind of motors used in ceiling fan and wet grinders?

Ceiling fan – Capacitor start and capacitor run single phase induction motor, wet grinders – Capacitor start capacitor run single phase induction motor.

14. What is the application of shaded pole induction motor?

Because of its small starting torque, it is generally used for small toys, instruments, hair driers, ventilators.etc.

15. In which direction a shaded pole motor runs?

The rotor starts rotation in the direction from unshaded part to the shaded part.

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Anna University 3rd SEM ECE EEI Lecture Notes