New Cogging Torque Reduction Methods for Permanent Magnet Machine

Abstract

Abstract. Permanent magnet type motors (PMs) especially permanent magnet synchronous motor (PMSM) are expanding its limbs in industrial application system and widely used in various applications. The key features of this machine include high power and torque density, extending speed range, high efficiency, better dynamic performance and good flux-weakening capability. Nevertheless, high in cogging torque, which may cause noise and vibration, is one of the threat of the machine performance. Therefore, with the aid of 3-D finite element analysis (FEA) and simulation using JMAG Designer, this paper proposed new method for cogging torque reduction. Based on the simulation, methods of combining the skewing with radial pole pairing method and skewing with axial pole pairing method reduces the cogging torque effect up to 71.86% and 65.69% simultaneously. IntroductionFor the last decade, the demand of permanent magnet motors (PMs) with wide application prospect are receiving spotlight due to the advance development of high performance permanent magnet materials and manufacturing technology. In various PM motors, an interior-type permanent magnet motor (IPM) which magnet are inserted inside the rotor rather than bounding the surface shows better performances in flux weakening operation and achieve higher flux density due to the small air gap that allows to impose a magnetizing current effectively [1]. IPM motors are commonly used for industrial drives, electrical vehicle applications and generation systems as it has high element execution, and vitality change efficiency. However, due to PM air gap length, IPM create an extensive cogging torque issues.The cogging torque or also known as detent torque and 'no-current' is a famous issue, which happened in PM motors. The components of cogging torque are produce by the interaction PM and slotted iron structure, and shows itself by the propensity of a rotor to adjust in various stable positions even when a motor is not energized. This deteriorates the machine operation, performance of position control system, generating acoustic noises and vibrations, speed pulsations, harmonics distortion, and premature wear of the bearings during low speed [2]. The communications between PMs mounted on the rotor and anisotropy began by stator windings slots raised the cogging torque and variations of the magnetic field energy during the rotation, as indicated by [3]:

A New Technique to Reduce the Cogging Torque of Integral Slot Number in Permanent Magnet Synchronous Machine

“…The advantages of this technique laid in the fact that by employing the TSS technique in magnet edge, another CT reduction technique might gather. The other CT reduction technique could be included in this method by implementing this method, such as bread loaf [17], optimize magnet pole arc [19], reducing magnet volume [17], increasing air gap length between the stator core and magnet pole [27].…”

“…In this paper, the magnets of PMSMs studied have been assumed to be unity and the effect of machine has been neglected. The flux magnetic density in the air gap of PMSMs are coupled with remnant flux density B r , and calculated as in Equation (6) [27], [17]. = , -.…”

“…Based on equation 1, the CT peak value for all experimental machines can be calculated. The impact of the magnet on the two steps of slotting in magnet edge to the CT could be analyzed using Equations (1), (2), and ( [27]. The advantage of combination of FEMM and LUA increased a quick execution for the implementation of a complete simulation of a specific PMSM.…”

“…The reports related to the CT reduction technique and its achievement also well documented in worldwide. Some CT reduction techniques has been applied in PMSM design such as such as to shift or segmented of the magnet pole [1], to skew or step skewing magnet [2]- [8], to optimize the magnet pole arc [7]- [14] magnet slotted [2]- [6] [8][15] to shape the magnet [13] [16]- [22], to employ dummy slot at stator core and dummy teeth at stator [11] [15][23]- [26], combining the skewing with radial pole pairing method and skewing with axial pole pairing method reduces [27], CT reduction in Brushless Motors by a Nonlinear Control Technique [28]. However, the most effective technique to reduce the CT in PMSM with integral slot number of 48 slot / 6 pole is by employing two steps of slotting in the magnet edge of the machine.…”

Novel of Cogging Torque Reduction Technique for Permanent Magnet Generator by Compounding of Magnet Edge Shaping and Dummy Slotting in Stator Core

“…From stator side, the slot opening was optimized [32], stator shoe depth variation [18], magnet-shaping [6], [11], [12], [14], [15], [17], [25]- [27], [41], magnet pole-arc [31], [34], [36]- [39], dummy-slotting, [8], [9], [28], [42]- [45], stepped slot opening [32]. In fact, every CT reduction technique implemented in PMGs structure has its own characteristics and advantages.…”