Page 720 - Basic Electrical Engineering

Substituting values,

That is, the starting torque is only 4 per cent of the maximum torque.

Example 8.12 No-load test and blocked-rotor test were performed on a 10
hp, four-pole, 400 V, 50 Hz, three-phase induction motor to determine its
efficiency. The test data are given as follows:

no-load test: V = 400 V, I = 6 A, P = 300 W
blocked-rotor test: V = 40 V, I = 24 A, P = 700 W

Calculate the efficiency of the motor on full load.

Solution:

2
Losses under blocked-rotor test is considered equal to I R losses in the two
windings. If R is the equivalent resistance of the two windings referred to
e
stator side, then total copper loss

2
At no load, I R loss in the windings