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Electrical machines such as motors are designed to withstand a certain maximum rated current (continuous) and a fault condition current for a short duration only.
In order to practically verify this capability, a locked rotor test is performed on the motor as part of the final factory acceptance test. The motor rotor is mechanically locked and rated current is applied to the stator winding incrementally, starting from zero, all at rated supply voltage and frequency. Motor stator winding temperature is monitored and also the shaft output torque can also be calculated, if a load cell or strain gauge is connected to the torque arm.
Therefore this locked rotor test (which is equivalent of a short circuit test for a generator) is used to verify the maximum current handling capability of the motor.
Anush GE
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∙ 14y ago
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What is difference of blocked rotor and locked rotor protection of motor?
What is difference of blocked rotor and locked rotor protection of motor?Read more:What_is_difference_of_blocked_rotor_and_locked_rotor_protection_of_motor
What are No Load And Locked Rotor tests on a three phase induction motor?
Doing a No Load test of a 3-phase induction motor involves the measuring of current, voltage, torque etc with no load on the rotor shaft, meaning that it is free to turn but is not driving anything else. Similarly a Locked Rotor test involves the measuring of current, voltage, torque etc with the rotor shaft "locked" i.e. prevented from turning, which is the worst loading condition the motor would ever have to contend with.
What is locked rotor?
Locked rotor current is the amount of current a motor would draw if you energize the motor and the rotor (the spinning shaft) doesn't spin.
What are No Load And Blocked Rotor tests on a three phase induction motor?
There is no such thing as a "Blocked" Rotor test so that must be a misunderstanding of the correct description, which is "Locked" Rotor test.For more information see the answer to the Related Question shown below.
What is LRA of a motor?
Locked rotor ampere
What is a locked rotor?
A rotor that doesn't move. Usually manually activated or automatically activated.
How do you test a compressor?
To test a compressor if locked up read the tag on compressor for locked rotor amps, then bypass safety therm-o-switch found under protective black cover on compressor, and with a clamp-on amp meter momentarily run compressor to check amperage.
How do you measure lock rotor amps?
Compressor locked rotor amps are measured with an amp-probe or clip on ampmeter. Lock rotor amps are amps with the rotor not turning/moving, and the winding at ambient temperature. locked rotor amps are X4.5 to X5 times the FLA of motor name plate.
How do you measure compressor lock rotor amps?
Compressor locked rotor amps are measured with an amp-probe or clip on ampmeter. Lock rotor amps are amps with the rotor not turning/moving, and the winding at ambient temperature. locked rotor amps are X4.5 to X5 times the FLA of motor name plate.
What wattmeter indicate for blocked rotor test?
There is one thing that watt-meter indicates of blocked rotor test. That is the voltage flows and in blocked rotor test.
What is LRPDV?
LRPDV is Locked Rotor Pull-down Voltage.
What is the locked rotor current on a 3 ton air conditioner?
You need to first know the wattage of the motor and locked rotor current can be tested at a lab only
