October 27, 2020 February 24, 2012 by Electrical4U. The important characteristics normally shown by a squirrel cage induction motors are crawling and cogging. These characteristics are the result of improper functioning of the motor that means either motor is running at very slow speed or it is not taking the load.
What is cogging and crawling of induction motor?
A.Cogging can also be reduced by using skewed rotor. Q.What is Crawling? A: It has been observed that squirrel cage type induction motor has a tendency to run at very low speed compared to its synchronous speed, this phenomenon is known as crawling. The resultant speed is nearly 1/7th of its synchronous speed.
What is meant by crawling 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.
What is mean by cogging?
Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a Permanent Magnet (PM) machine. It is also known as detent or ‘no-current’ torque. … Cogging torque is an undesirable component for the operation of such a motor.
How do you stop an induction motor from crawling?
What is meant is to arrange the stack of rotor laminations so that the rotor slots are “skewed” or angled with respect to the axis of rotation. Constructing the rotor with skewed slots and providing more (or fewer) rotor slots than stator slots is the remedy for both cogging and crawling.
What is cogging how cogging effects can be reduced?
To reduce cogging in Iron Core linear motors, Tecnotion has taken two measures. First, the magnet plate is constructed with a skewed magnet arrangement that smooths out the movement of the iron core. Second, Tecnotion Iron Core motors use a proprietary coil laminate that is specifically designed to reduce cogging.
Why can’t an induction motor run 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 . …21 мая 2018 г.
What is synchronous speed?
Synchronous speed is a significant parameter for the rotating magnetic field-type AC motor. It is determined by the frequency and the number of magnetic poles. Synchronous speed No = [rps, revolutions per second] f = Frequency [Hz]
What is Torque slip characteristics of induction motor?
The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine.
Which type of motor has high starting torque?
DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load. DC motor has high starting torque.In a series motor the same current flows through the armature and the field winding.
What is a induction motor and how does it work?
An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor.
How do you reduce cogging torque?
The most effective way to reduce cogging torque is skewing of stator slots or rotor poles. It means skewing of one side of stator (rotor) core by few degrees in according to the other side of core (Fig. 7). The skewing allows to eliminate the cogging torque or to reduce it to minimum.
What causes motor cogging?
Introduction. Cogging is an undesirable characteristic of some permanent magnet motor designs. It’s also known in stepper motors as ‘detent’ or ‘no current’ torque. Cogging torque is generated when the sides of the rotor teeth line up with the sides of the stator teeth within the motor.
What is speed control of induction motor?
In this method, speed of an induction motor is controlled by injecting a voltage in rotor circuit. … If we inject emf which is in phase with the rotor induced emf, rotor resistance will decrease. Thus, by changing the phase of injected emf, speed can be controlled.
What is double cage induction motor?
A Double Cage Induction motor is that type of motor in which a double cage or two rotor windings or cages are used. This arrangement is used for obtaining high starting torque at a low value of starting current. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor.