Parameters do We Get From no Load Test and Blocked Rotor Test on 3-Φ Induction Motor
Q. What data / parameters do we get from no load test and blocked rotor test on 3-Φ induction motor.
No load test and blocked rotor test :
Equivalent leakage reactance = X01= √ [Z01]2 _[R01]2
Form the no load test and blocked rotor tests the magnetic circuit constants and electric circuit constants are found out. So equivalent circuit of induction motor can be drawn.
The efficiency can be calculated as follows :
% Efficiency = O/P / O/P+ (losses) X 100
= O/P / O/P+ Iron loss+ Copper loss X 100
= O/P / O/P +W0 + WC X 100
The data obtained from these tests is helpful in drawing the circle diagram from which the performance of the motor can be judged.
If required, the voltage can be raised in steps and readings of current, wattmeter (power I/P) are taken, until the current reaches not more than twice the normal value. Figure shows these typical test results. It is seen that the power-curve is a parabola because input on short circuit is entirely I2R loss. The impedance is seen to fall with higher currents, it is due to saturation effect.
