Question

During blocked rotor test on an induction motor, the power is drawn mainly for 
1. Core loss
2. Copper loss
3. Windage and frictionless
4. both (a) and (b)

Answer 1

Correct Answer - Option 2 : Copper loss

Blocked rotor test or short circuit test:

• It is used to find out series branch parameters (R01­ and X01) of equivalent circuit parameters when referred to the primary side (stator) and the full load copper losses (I2R).
• By applying rated voltage under a blocked rotor test, the motor will take very high short circuit current which is equivalent to 5 to 8 times of the full load current.
• We need to apply reduced voltage initially and increase the voltage up to the current drawn by the motor reaches the rated current.

Note:

A no-load test or open circuit test is used to find the shunt branch parameters of the equivalent circuit and the constant losses. We can separate these constant losses into iron losses and mechanical losses.