Question 4
- A four pole three-phase induction motor operates from a supply of frequency 50 Hz. Calculate the synchronous speed.
- (i) state three methods of starting a three-pole inductor motor.
- state one application for each of the following single-phase induction motors:
- universal;
- capacitor start.
Observation
(b)(i) Methods of starting a 3 phase inductions motor
(i) Star – delta
(ii) Auto transformer
(iii) Direct on line
(iv) Rotor resistance starter
(b)(ii) Application of single phase motors
(i) Universal motor - Vacuum cleaner
- Food mixers
- Domestic sewing machine
- Portable drills
(ii) Capacitor start - Ceiling fan
- Compressors
- Refrigerators
- Air conditioners
The first part was well attempted by candidates but they could not provide correct answers for the other part.