Abstract
Permanent magnet (PM) motors are rapidly replacing the squirrel cage induction motors for its energy efficient operation, smooth control and high power density. Although PM Motors are energy efficient, they are inherently affected by cogging torque and torque ripple. Magnetic alignment between teeth of stator and permanent magnet of rotors produce cogging torque. Torque ripple is a dynamic oscillation during steady-steady operation which leads to various mechanical anomalies like vibration, noise and rotor stress. Torque ripple is produced in PM motors because of non-sinusoidal distribution of flux, saturation, improper selection of slots etc., these ill effects will deteriorate the starting and steady-state performance of motors. So it is very vital to make analysis and prediction of cogging torque and torque ripples to make the motor more effective. Now a day's minimizing the torque ripples and cogging torque are gaining importance in PM motor designs. In this proposed work, the cogging torque analysis and torque ripple analysis of permanent magnet motor and line start permanent magnet motor has been done and reported.
Highlights
Permanent magnet (PM) machines are gaining importance in many applications because of their high energy conversion efficiency, high power density, high energy density and low size alternative to conventional machines
The high precision drives requiring high quality of motion needs the development of PM motors with low electromagnetic cogging torque
This study explains the various methods of prediction and analyzes for determining torque ripples in PM motors and LSPMSM
Summary
PM machines are gaining importance in many applications because of their high energy conversion efficiency, high power density, high energy density and low size alternative to conventional machines. In this paper the various techniques and methods are proposed for the optimization of PMSM and LSPMSM motors These guidelines are useful for the designers to reduce torque ripple and cogging torque during design stage to achieve smoothness in developed torque. If the magnets are arranged symmetrically with the magnet width similar to pole pitch, the fundamental component of back electromotive force can reach maximum value with harmonic content causing significant torque ripples. It is important to get Analysis and Prediction of Cogging Torque and ripples in output Torque of Permanent Magnet Synchronous Motor and Line Start Permanent Magnet Synchronous Motor better arrangement of magnet to achieve compromise in between maximum value of fundamental component of back electro motive force and harmonic content producing ripples in the torque. In practice, an optimization procedure has to be followed to obtain pure sinusoidal EMF waveform with negligible torque ripple
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