Aux 2 Unit 5 3 Phase induction motor

3. 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

Answer

3. 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

Answer

2. 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

Answer

3. 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

Answer

3. 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

Answer