What is difference of blocked rotor and locked rotor protection of motor?
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Locked rotor ampere
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.
All motor circuits require protection against single-phasing.
A device with an overload protection used to control a motor is an Overload Relay.
The only time a motor should go into a locked rotor condition is if the motors connected load jams causing the motor to stop turning. At this point if the motor control circuitry is sized to the motor's full load amperage, the high rise in current will trip the motor off line.
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.
A motor that is locked up cannot make a rotation. The motor will not turn over or start. Try to turn the main pulley. When the pulley cannot be by just, the motor is locked up.
A motor with a totally blocked exhaust will start but immediately lose power then stall.
Locked rotor ampere
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.
A motors locked rotor current is the same as the motors starting current. This is the point where the voltage is applied to a non rotating motor, time cycle zero. Because the motor is not rotation and generating a back EMF to oppose the inrush current, the current will go as high as 6 times the running current of the motor.
In reality if the proper motor protection is used, no motor should burn. Even a motor that has a locked rotor will trip the heater overload protection. So the issues to be looked at that would cause a motor to burn would be, is the motor protection correctly sized? The motor must be running within the manufactures specifications and not outside the motors service factor. The supply breaker and wiring to the motor must be the correct size. The overload protection should be in mid scale of the settings. House keeping around motors is a big condition to keep a motor running within its parameters. Cooling fins and fans must be kept clean of any debris. All of this should allow a motor to run free of trouble for many years.
The letter "W" added in the grade of protection means that the electric motor has a protection against climatic agents like rain, salt spray, dew...etc.
The motor turns and doesn't start is it blocked?
blocked vs. random practice blocked vs. random practice
All motor circuits require protection against single-phasing.
A device with an overload protection used to control a motor is an Overload Relay.