What is no load torque 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 is similar to the open circuit test on transformer. Actually, to achieve synchronous speed in an induction motor is impossible. The speed is assumed to be synchronized.

What is no load torque?

The torque-speed curve begins at the crossing of the Y axis, where torque is maximum and speed is zero. This is the stall torque—the maximum torque when the motor is running at nominal voltage. This point is known as the no-load speed—the speed when running at nominal voltage and zero load.

Is the starting torque of an induction motor high or low?

So starting torque is low in induction motors. To get maximum starting torque, resistance is added to the rotor while starting slip ring motors, which is reduced gradually as motor picks up the speed. R2 is much smaller than X20 and at starting slip (s) is 1.

What is the starting torque of a 3 phase induction motor?

A 3-phase induction motor has a starting torque of 100\% and a maximum torque of 200\% of the full load torque.

What is starting torque and no load speed?

The start-up torque, although not marked, is the torque value at the far left of the plot (at zero speed). If your mechanical system has a higher start-up torque than this, then this motor will not be able to get it running even if the torque required to keep it running is lower than the full load torque.

What is the starting torque?

Starting torque is the torque transferred by the shaft coupling during run-up (see Start-up process). It is calculated based on the ratio of power (P) to angular velocity (ω) and is represented as a rotational speed function.

How do you find the starting torque of a motor?

We know that at the start the rotor speed, N is zero. So, the equation of starting torque is easily obtained by simply putting the value of s = 1 in the equation of torque of the three phase induction motor, The starting torque is also known as standstill torque.

Are Motors started under load?

Some motors can start under load, and some can’t. Where a motor is coupled to the load without an intervening clutch system on the load end, assume the motor cannot start under load unless you verify it can. And that generally means it needs to be a Design D motor, which has “extra high” starting torque.

What is the starting torque of an induction motor?

Starting Torque Formula for Induction Motor The starting torque of a motor is that torque which is produce by it at start. It is denoted by T st and corresponds to s = 1. So by substituting s = 1 in above expression, we get the expression for starting torque.

Why is there no load test in induction motor?

Theory of No Load Test of Induction Motor The impedance of magnetizing path of induction motor is large enough to obstruct flow of current. Therefore, small current is applied to the machine due to which there is a fall in the stator-impedance value and rated voltage is applied across the magnetizing branch.

What is the meaning of starting torque?

Torque is the turning force through a radius – with the units Nm in the SI-system and the units lb ft in the imperial system. The torque developed by an asynchronous induction motor varies when the motor accelerates from zero to maximum operating speed. Locked Rotor or Starting Torque

Why is small current required to produce adequate torque?

Small current is required to produce adequate torque. This test is also well-known as running light test. This test is used to evaluate the resistance and impedance of the magnetizing path of induction motor. The impedance of magnetizing path of induction motor is large enough to obstruct flow of current.