How do you test a blocked rotor?

Process of Testing of Blocked Rotor Test of Induction Motor In block rotor test, the low voltage is applied so that the rotor does not rotate and its speed becomes zero and full load current passes through the stator winding. The slip is unity related to zero speed of rotor hence the load resistance becomes zero.

Why no load test is performed at rated frequency and Blocked Rotor Test is performed at reduced frequency?

This test should be performed at a reduced frequency. In order to obtain accurate results, the Blocked Rotor Test is performed at a frequency 25 percent or less than the rated frequency. The leakage reactances at the rated frequency are obtained by considering that the reactance is proportional to the frequency.

Which test is carried out on synchronous motor?

These are the open circuit saturation test and the steady-state short circuit test (also known as the synchronous impedance test). In the open circuit test, the machine is run at rated speed with the stator winding open circuited.

How can the Blocked Rotor Test be performed to obtain induction motor characteristics in synchronous speed?

As in Transformer short circuit test, we apply a voltage which can circulate rated current in the winding, likewise in Blocked Rotor Test we apply a Voltage to the Stator winding of an Induction Motor by using VARIAC so that rated current flows through the stator winding.

Why blocked rotor test are used?

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).

How do you test an induction motor rotor?

HIGH CURRENT ROTOR TEST – This test is performed by applying high current through the shaft of the rotor (rotor out of stator) and thermally scanning (infrared or thermoscan) the rotor O.D. searching for shorted laminations. These shorted laminations cause localized hot spots which cause uneven heating of the rotor.

Why perform no load and blocked rotor test?

For larger motors it may be difficult to arrange loads for them. Moreover power loss will be large with direct loading tests. Thus no load and blocked rotor tests are performed on the motors. The synchronous speed can be achieved by taking slip = 0 which creates infinite impedance in the rotor branch.

Which test is carried out on synchronous motor before assembly?

Bearing insulation is conducted on synchronous motor before machine assembly.

What is short circuit test in synchronous machine?

Short-Circuit Test Set the field current to zero. Short circuit the armature terminals. Drive the generator at synchronous speed with external mechanical system. Slowly increase the field winding current until the short circuit armature current reaches the rated design value.

What is blocked rotor test in induction motor?

A blocked rotor test is conducted on an induction motor. It is also known as short circuit test, locked rotor test or stalled torque test. From this test, short circuit current at normal voltage, power factor on short circuit, total leakage reactance, and starting torque of the motor can be found.

What do you mean by blocked rotor test?

In the blocked rotor test, the rotor is locked securely enough that it cannot break free. 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.

What is the purpose of performing no load test and block rotor test?

1. To obtain the variation of no load power and current and blocked rotor power and current with changes in the applied voltage to the stator. 2. To determine the equivalent circuit parameters of an induction motor.