What is unbalanced magnetic pull in induction motor?
If the rotor of an induction motor is not concentric with the stator then an electromagnetic force is generated in a direction that will increase the eccentricity. This is called unbalanced magnetic pull (UMP). These account for any winding configuration including parallel stator winding connection.
What are the practical aspects of unbalanced magnetic pull?
UMP can create a bending motion of an outer stator electrical machine (especially in clamped-free conditions), resulting in air-borne acoustic noise. UMP can also excite the inner rotor shaft bending mode, resulting in structure-borne acoustic noise.
What is crawling and cogging?
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 will happen if we increase the air gap in the induction motor *?
Detailed Solution. If the air gap of an induction motor increases, 1) The permeability of the magnetic circuit rotor-to-stator will decrease. 2) The magnetizing inductance of the motor thus decreases.
What is clogging and crawling?
What is the slip?
Slip is the differentiation between synchronous and asynchronous speed. The difference between the synchronous speed of the electric motor magnetic field, and the shaft rotating speed is slip – measured in RPM or frequency. Slip increases with increasing load – providing a greater torque.
What happens if the air gap becomes more or less?
Longer air gap means increased reluctance and leakage flux. Therefore the value of air gap flux reduces. This in turn reduces EMF induced in the rotor bars, rotor current and torque. Apart from this, longer air gap length will also cause to have poor power factor and hence associated losses will also increase.
What happens if the air gap length is doubled?
What happens if the air gap length is doubled? If the air gap of an induction motor is doubled then the mmf and magnetizing current approximately doubles. Also increase in air gap length increases the overload capacity, offers better cooling, reduces noise and reduces unbalanced magnetic pull.
What is rotor EMF?
Rotor EMF. When the rotor is stationary, the 3-phase induction motor behaves as a 3-phase transformer with secondary winding short circuited. Thus, the per phase induced EMF in the rotor (or secondary) is given by, RotorEMF/Phase,πΈ2=πΈ1Γπ2π1=πΎπΈ1β¦(
What is NS and NR?
In the above equation, ‘Ns’ is the synchronous speed in rpm whereas the ‘Nr’ is the rotational speed in the rpm (revolution for each second)
How does the rotor become magnetic?
In a three-phase induction machine, alternating current supplied to the stator windings energizes it to create a rotating magnetic flux. The flux generates a magnetic field in the air gap between the stator and the rotor and induces a voltage which produces current through the rotor bars.