Rotor conductors are skewed because of the following reasons: Primarily to prevent the Cogging Phenomenon. It is a phenomenon in which, if the rotor conductors are straight, there are chances of magnetic locking or strong coupling between Rotor & Stator.
Why are the rotor slots skewed in some rotors?
Many rotor designs are skewed. So, why are rotors skewed? As the rotor turns, discontinuities on the surface of the rotor and stator disrupt the magnetic flux path of the motor. The flux path variation shows up in the form of harmonics that affect the performance of the motor.
What is the reason for skew slot in a rotor of a three phase induction motor Mcq?
Explanation: Rotor bars are skewed to prevent cogging effect. When an induction motor refuses to start even if full voltage is applied to it, this is called as cogging. Starting torque of an induction motor depends on the product of the magnitude of stator and rotor current and sine of the angle between both.
Why the rotor bars are mounted in a slightly skewed position in 3 phase motor?
Also the rotor bars are usually not quite parallel to the rotor shaft but are mounted in a slightly skewed position. This feature tends to produce a more uniform rotor field and torque. Also it helps to reduce some of the internal magnetic noise when the motor is running.
What is the function of starter in induction motor?
⇒ The starter is a device which is basically used to limit the starting current by supplying reduced voltage to the motor at the time of starting.
What is meant by cogging?
The permanent magnets produce an attraction force to all magnetic materials. Cogging is an result of the iron core motor design. The iron core has “preferred” positions relative to the magnets, and the motor must vary its thrust force to overcome these positions.
Why rotor skewing is used in a 3 phase squirrel cage induction motor?
Since the skewed rotor slot is not parallel to the start slot in an induction motor, there is more leakage reactance. … The skewing of the rotor reduces the tooth harmonics, and thus prevents the crawling effect. Reduces Magnetic Hum: The skewing helps in reducing the magnetic hum, and the motor runs quieter.
What happens if 50 harmonics is given to induction motor?
What happens if fifth multiples of harmonics is given to induction motor? It will rotates in reverse direction. Fail to start. It will rotates in normal operation.