ETO ETO Exam papers 📅 Jun 2025

Exam Question

With reference to three phase induction motors

(a) Explain the phenomenon of crawling and cogging in these motors. (6)

(b) A three-phase induction motor is wound for four poles and is supplied from a 50 Hz system. Calculate: (10)

(i) The synchronous speed

(ii) The speed of the rotor when the slip is 4 per cent

(iii) The rotor frequency when the speed of the rotor is 600 r/min.

Reference Answer

(a) Explain the phenomenon of crawling and cogging in these motors
Crawling (Low-speed running)
What it is: Motor runs at a very low speed (about 1/7 of normal speed).
Why it happens: Due to 7th harmonic in the magnetic field from the supply.

Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.

View plans Browse library

← Browse more questions

Prepare on Android — MeoMock on Google Play