what is meant by Locked Rotor Current and Locked Rotor Torque in Motor?

The Locked Rotor Torque or Starting Torque is the torque the electrical motor develop when its starts at rest or zero speed.

A high Starting Torque is more important for application or machines hard to start – as positive displacement pumps, cranes etc. A lower Starting Torque can be accepted in applications as centrifugal fans or pumps where the start load is low or close to zero.

The Locked Rotor Current or Starting Current is the torque the electrical motor develop when its starts at rest or zero speed.

Induction motors usually have the highest starting current/torque as compared to other motors

This Site Might Help You.

RE:

what is meant by Locked Rotor Current and Locked Rotor Torque in Motor?

https://shorturl.im/ayjXn

The link below shows the “V” curve for a synchronous motor, where the power factor changes with the field excitation current. The supply current also changes, as there are “reactive” currents added when the power factor is less than 1, whether capacitive or inductive. Additionally you will notice that the current for no load is less than the current for full load at any given field excitation current. Note that there is only synchronous speed. If there is slip it is overloaded and the excitation would be disconnected.. As the load changes the rotor chages its position with regard to the rotating field, but is still rotating at the same speed. If your motor is a small type with a permanent magnet field (as it seems from the currents you mentioned), it may be just that the gearbox is causing this effect. Often the gearbox has such a high ratio that the output load torque has little or no effect on the motor current. The current drawn is due to the gearbox load, its mechanical friction. The load may effect the efficiency of the gearbox in some way, for example the clock style gears may tend to align better when loaded, especially if it is worn or the lubricant is a bit old.. Note also these motors tend to start in a random direction, so it may be direction dependant. I expect the non synchronous (overloaded) operation with these is intended to be self protecting if stalled, by having sufficient leakage reactance to limit the supply current. This is through gaps in the magnetic circuit. In the second link you will find a description of how these motors (electric clock motors) are built with a ring of tabs on a single coil and a cup like rotor that acts as an induction motor when required. A bar magnet in this rotor makes it “lock into synchronous” when the speed is sufficient. This construction allows the motor to start by itself. In this kind of motor the current when not synchronous could be less than the synchronous current for a variety of reasons. Even the slightest change in speed means it is no longer synchronous. The motors in microwave ovens are like this too. Nevertheless, try cleaning up the lubricant first to see what effect that has.

Locked Rotor Amps

The first parameter is the highest current flow when the electric motor does not turn, but the rotor is locked so it can not turn.

The second parameter is similar: The rotor is “locked” with a torque meter and the current as measured in the first parameter produces a torque at standstill which is measured for this parameter.

Stop a free running motor by applying just enough force on the shaft and measure the current in the motor supply circuit. This is the locked motor current in ampere.. In the same way, the force applied on the shaft just enough to stop the rotation of a free running motor is the torque expressed as force x distance (newton.meter)

A PHENOMEON OF TRANSFORMATION WILL TAKE PLACE , SIMILAR TO AS IN TRANSFORMER. ONE SIDE WINDING WILL WORK AS PRIMARY WINDING AND OTHER WINDING WILL WORK AS SECONDARY WINDING,

ernst, gave you thee best answer