Blocked rotor test

Method

In the blocked rotor test, the rotor is locked. A low voltage is applied on the stator terminals so that there is full load current in the stator winding, and the current, voltage and power input are measured at that point. When the rotor is stationary, the slip, s = 1 . The test is conducted at 1 / 4 the rated frequency as recommended by IEEE, because the rotor's effective resistance at low frequency may differ at high frequency. The test can be repeated for different values of voltage to ensure the values obtained are consistent. As the current through the stator may exceed the rated current, the test should be conducted quickly. By using the parameters found by this test, the motor circle diagram can be constructed.

Short circuit current at normal voltage

I S is the short circuit current at voltage V S
I S N is the short circuit current at normal voltage V
I S N = I S × V V S

Short circuit power factor

W S is the total input power on short circuit
V S L is the line voltage on short circuit
I S L is the line current on short circuit
c o s ϕ S is the short circuit power factor
c o s ϕ S = W S 3 V S L I S L

Leakage reactance

Z 01 is the short circuit impedance as referred to stator
X 01 is the leakage reactance per phase as referred to stator
Z 01 = short circuit voltage per phase short circuit current = V S I S

W c u is the total copper loss
W c is the core loss

W c u = W S − W c
W c u = 3 × I S 2 R 01

R 01 = W c u 3 I S 2

X 01 = Z 01 2 − R 01 2