A blocked rotor test is normally performed on an induction motor to find out the leakage impedance. Apart from it, other parameters such as torque, motor, short-circuit current at normal voltage, and many more could be found from this test. Blocked rotor test is analogous to the short circuit test of transformer.
What is blocked rotor test in induction motor?
The Blocked Rotor Test of an induction motor is similar to the short circuit test of a transformer. In this test, the shaft of the motor is locked so that it cannot move and the rotor winding is short-circuited. In the slip ring motor, the rotor winding is short-circuited through the slip rings.
Why do we perform no load and blocked rotor test on induction motor?
The efficiency of small motors can be determined by directly loading them and by measuring the input and output powers. The power loss will be large if we directly test the load. … Therefore indirect methods are used to determine the efficiency of 3-phase induction motors.
Why must we supply rated current at blocked rotor test condition instead of rated voltage?
The test is conducted at low voltage because if the applied voltage was normal voltage then the current through the stator windings would be high enough to overheat the windings and damage them. The blocked rotor torque test is not performed on wound-rotor motors because the starting torque can be varied as desired.
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.
What is load test of induction motor?
The load test on induction motor is performed to compute its complete performance i.e. torque, slip, efficiency, power factor etc.
What is no load test of 3 phase induction motor?
No Load Test is an indirect method used for determining the efficiency and also to determine the circuit parameters of the equivalent circuit of the three-phase induction motors. The open-circuit test is performed on the transformer. The no-load test is the same as the open-circuit test performed on the transformer.
Why no load test is performed in induction motor?
As the name suggest no load test is performed when rotor rotates with synchronous speed and there is no load torque. … This test gives the information regarding no-load losses such as core loss, friction loss and windage loss. Rotor copper loss at no load is very less that its value is negligible.
What are the main objectives of blocked rotor and no load tests of an induction motor?
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.
What are the types of induction motor?
Types of Induction Motor: A Concise and Useful Guild
- Types of Induction Motors. Types of Single-Phase Induction Motors. Split Phase Induction Motors. 2&3. Capacitor Start and Capacitor Start Capacitor Run Induction Motors. Shaded Pole Induction Motors. Types of Three-Phase Induction Motors. Squirrel Cage Induction Motor. Slip-ring or Wound Rotor Induction Motor.
What is locked rotor current?
Locked rotor current is basically the current drawn by the motor at its rated voltage when its rotor is kept stationary or in other words rotor is not spinning or rotating. So when we start a motor, its rotor is already at rest. This means, starting current and locked rotor current should be same.
What is crawling in induction motor?
Crawling of Induction Motor
It has been observed that squirrel cage type induction motor has a tendency to run at very low speed compared to its synchronous speed, this phenomenon is known as crawling. The resultant speed is nearly 1/7th of its synchronous speed.
Why UPF wattmeter is used in blocked rotor test?
Resistive circuits have unity power factor hence UPF wattmeters are used to measure power in these circuits. … As secondary side is short circuited the entire coil will be purely resistive in nature.So the power factor will be unity. So UPF(Unit Power Factor) Wattmeter is used in SHORT CIRCUIT TEST of Transformer.
Why rotor is short circuited?
When we give supply to the stator of motor, flux produces due to stator current. This flux cuts the rotor conductors and an emf is induces in the rotor circuit. But for flowing the current, circuit must be completed. So we short circuit the rotor conductors.
How do you check a rotor with a multimeter?
Connect one probe of the ohmmeter to a slip ring and the other to the shaft. The resistance should be infinite; a low reading indicates that the rotor may be grounding out and needs to be replaced.
How do you test a motor?
You should test the windings for a “short to ground” in the circuit and open or shorts in the windings. To test your motor for short to ground, you’ll need to set the multimeter to ohms and disconnect the motor from its power source. Then inspect each wire and look for infinite readings.