A Cogging Torque Minimization Procedure for Interior Permanent Magnet Synchronous Motors Based on a Progressive Modification of the Rotor Lamination Geometry

Abstract

This article describes a simple cogging torque minimization procedure for interior permanent magnet synchronous machines (IPMSMs), consisting of a progressive modification of the rotor lamination geometry. This procedure can be generalized for the main topologies of PMSM, independently of the number of stator slots or the location of the permanent magnets. For this purpose, a basic IPMSM structure is analyzed by means of the FEM (finite element method) approach, and then, several other IPMSM geometries, obtained by adequately modifying the rotor lamination geometry of the basic IPMSM model without changing its stator configuration, are proposed and discussed. The trends of the cogging torque generated by each model are computed and compared. From this comparison, it is demonstrated that, by simply acting on the shape of the rotor lamination and by choosing the optimized pattern, the cogging torque components can be theoretically canceled.

An In-Phase Unit Slot-Opening Shift Method for Cogging Torque Reduction in Interior Permanent Magnet Machine

“…As both κ and λ are prime numbers, the sin(πκn/λ) term is non-zero, while the sin(πκn) term is zero. Therefore, (13), or its derived (17) becomes zero when the ratio of n/λ is a non-integer.…”

“…The first category is rotor-side optimization. Caruso et al [13,14] proposed a simple cogging torque minimization procedure for IPM machines by changing the rotor lamination geometry. The proposed method was essentially similar to the PM-chamfering method in SPM machines, and the main idea of both was to reduce cogging torque by changing the air gap permeance.…”

High-Speed Design with Separated Tapering for Reducing Cogging Torque and Torque Ripple of a 3 kW Dry Vacuum Pump Motor for the ETCH Process

“…As expressed in Equation ( 4), the torque ripple increases as the range of torque fluctuation increases [1]. There are two causes of such large torque amplitudes: the input current and the mechanical structure of the motor [4,5]. First, the torque follows the peak value of the current, and the ripple frequency increases with the number of phases and rotating speed.…”

“…First, the torque follows the peak value of the current, and the ripple frequency increases with the number of phases and rotating speed. Ripple with respect to the mechanical structure is a matter of geometry [4,5]. Ripple occurs due to the structure of the electric motor, which has slots in the stator where the windings are wound.…”

“…By modifying the motor's shape to reduce cogging torque, torque ripple can be minimized. By altering the surface shape of the rotor core to reduce harmonic content in the airgap flux density, cogging torque and torque ripple can be reduced [4,5]. While tapering the rotor surface can reduce cogging torque and torque ripple, it also results in a simultaneous reduction in output [6].…”