28th November 2019

quora

10

Why rotor speed is always less than synchronous speed?

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An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach

How rotating magnetic field is produced in the stator?

The stator of the motor consists of overlapping winding offset by an electrical angle of 120°. When the primary winding or the stator is connected to a 3 phase AC source, it establishes a rotating magnetic field which rotates at the synchronous speed.

What is the difference between synchronous speed and rotor speed?

Induction motor with squirrel cage rotor has two different speeds. The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor's. The rotor speed will be always slower than the stator speed, we call it slip.

1

What is the slip speed of an induction motor?

Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol 'S'.

2

What is cogging in induction motor?

Sometimes, squirrel cage induction motors exhibits a tendency to run at very slow speeds (as low as one-seventh of their synchronous speed). This phenomenon is called as crawling of an induction motor. This action is due to the fact that, flux wave produced by a stator winding is not purely sine wave.

3

Why is an im also known as an asynchronous motor?

Induction motor works on the principle of induction i.e., when the power supply is given to the stator, it produces rotating magnetic field which gets induced in the rotor of induction motor causing rotor to rotate. As they run at Asynchronous speed they are called Asynchronous motor.

4

What is meant by induction motor?

Definition of induction motor. : an alternating-current motor in which torque is produced by the reaction between a varying magnetic field generated in the stator and the current induced in the coils of the rotor.

5

Why an induction motor Cannot develop torque when running at synchronous speed?

An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach

6

How do you start an induction motor?

A single phase induction motor requires separate starting circuitry to provide a rotating field to the motor. The normal running windings within such a single-phase motor can cause the rotor to turn in either direction, so the starting circuit determines the operating direction.

7

What happens when the speed of an induction motor reaches the synchronous speed?

2)If you drive it by external force to gain synchronous speed, or won't generate torque. If you mean that rotor runs at synchronous speed as the field of the stator , this will cause that slip to be zero , then there will be no torque generated in rotor , then rotor will be at standstill.

8

Why an induction motor is also known as rotating transformer?

An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. This changing magnetic field pattern can induce currents in the rotor conductors.

9

What is the principle of induction motor?

Basic working principle of an Induction Motor. In a DC motor, supply is needed to be given for the stator winding as well as the rotor winding. But in an induction motor only the stator winding is fed with an AC supply. Alternating flux is produced around the stator winding due to AC supply.

10

Why the synchronous motor is not self starting?

This is because the speed with which rotating magnetic field is rotating is so high that it is unable to rotate the rotor from its initial position, due to the inertia of the rotor. So under any case, whatever may be the starting position of the rotor, synchronous motor is not self starting.

11

How does a DC motor work?

How does a DC Motor work? The DC motor is a machine that transforms electric energy into mechanical energy in form of rotation. Its movement is produced by the physical behavior of electromagnetism. DC motors have inductors inside, which produce the magnetic field used to generate movement.

12

What is meant by slip in an induction motor?

Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol 'S'.

13

What is in a DC motor?

A DC motor is any of a class of rotary electrical machines that converts direct current electrical energy into mechanical energy. The most common types rely on the forces produced by magnetic fields.

14

What is meant by AC motor?

An AC motor is an electric motor driven by an alternating current (AC). The AC motor commonly consists of two basic parts, an outside stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft producing a second rotating magnetic field.

15

Why the induction motor is self starting?

Consider a 3-phase induction motor: A 3- phase supply to the armature produces a rotating magnetic field. This flux being linked to the rotor coils, induces voltage and produces current in the rotor. The current carrying rotor being placed in a magnetic field, experiences a torque and hence begins to rotate.

16

How many types of induction motors are there?

Three-Phase Induction Motor: These motors are self-starting and use no capacitor, start winding, centrifugal switch or other starting device. Three-phase AC induction motors are widely used in industrial and commercial applications. These are of two types, squirrel cage and slip ring motors.

17

Can motor act as a generator?

Yes we can say DC motor act as a generator and we talk about its functionality , you can turn an electric motor into a generator to generate power, as this video proofs. If dc supply is given to the armature,then it act as a motor converting electrical energy into mechanical energy.

18

What is a rotor assembly?

The rotor is a moving component of an electromagnetic system in the electric motor, electric generator, or alternator. Its rotation is due to the interaction between the windings and magnetic fields which produces a torque around the rotor's axis.

19

What is the principle of motor?

Working principle of a DC motor. A motor is an electrical machine which converts electrical energy into mechanical energy. The principle of working of a DC motor is that "whenever a current carrying conductor is placed in a magnetic field, it experiences a mechanical force".

20

How does an induction motor work?

The Working of an Induction Motor. Fig.7 Squirrel cage rotor which is the most commonly used one in induction motors. A 3 phase AC current passing through a Stator winding produces a rotating magnetic field. So as in the previous case, current will be induced in the bars of the squirrel cage and it will start to rotate

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