Aux 2 Unit 5 3 Phase induction motor

  1. With reference to variable speed control of a 3 phase ac induction motors:
    (a) explain why EACH of the following is not preferred:
    (i) variable voltage, constant frequency;(3)
    (ii) variable frequency, constant voltage.(3)
    (b) explain why voltage and frequency should both be varied. (4)

Aux 2 Unit 5 Q1

Aux 2 Unit 5 Quiz 1

  1. With reference to a solid state (inverter) starter for a 3 phase induction motor:
    (a) explain the starting characteristics of this system;4)
    (b) list the advantages and disadvantages when compared to conventional starting methods.(6)

Aux 2 Unit 5 Q2

Aux 2 Unit 5 Quiz 2

  1. Describe, with the aid of a sketch, a variable frequency drive for speed control of a three phase motor.(10)

Aux 2 Unit 5 Q3

Aux 2 Unit 5 Quiz 3

  1. With reference to speed control of ac induction motors, explain the function of Pulse Width Modulation (PWM).
    (10)

Aux 2 Unit 5 Q4

Aux 2 Unit 5 Quiz 4

  1. Explain what happens to the output voltage of an a.c. generator from sudden application of a large load to a steady state condition.(10)

Aux 2 Unit 5 Q5

Aux 2 Unit 5 Quiz 5