Techniques for Reduction of the Cogging Torque in Claw Pole Machines with SMC Cores

Abstract

Abstract:As one of the main parasitic parameters in permanent magnet (PM) synchronous machines (PMSMs), cogging torque is the main component of the torque ripple, which has always been the handicap in the high-performance, low-speed drive systems. Over the last two decades, various methods have been proposed to decrease the cogging torque in both radial-flux and axial-flux PMSMs. Among these methods, stator slot skewing, stator tooth notching, PM skewing, PM shifting, and pole pairing are extensively investigated. However, little work has been done on reducing the cogging torque of the claw pole machine (CPM), whose cogging torque cannot be ignored. In this paper, the general methods that have been used to reduce the cogging torque in radial-flux and axial-flux PMSMs are developed and verified in a CPM with a soft magnetic composite (SMC) core. The 3-D finite element method (FEM) is used to calculate the cogging torque and PM flux linkage per turn. By comparing different cogging torque reduction technologies, it can be found that the magnet step skewing and unequal claw pole width are very suitable for CPM.

Design Issues for Claw Pole Machines with Soft Magnetic Composite Cores

“…The magnet skewing rotor and its definition of skewing angle are illustrated in Figure 9. In [5], various kinds of methods were adopted for the cogging torque reduction of this kind of machine, and an accurate skewing angle is obtained. In addition, the unequal claw pole tooth is another way to reduce the cogging torque of CPM.…”

“…Due to the adopted use of global ring winding, the torque coefficient of a transverse flux machine (TFM) is proportional to its number of pole pairs, and thus the torque density of TFM is higher than the other electrical machines [2][3][4][5][6]. The concept of TFM was is first proposed in 1885 by W.M.…”

“…In [19], by using the multilevel design optimization method, this CPM was optimized, and its electromagnetic (EM) torque can achieve about 0.52 Nm while with the material cost is reduced greatly. In [5], the unequal stator claw teeth and other methods were investigated to reduce the cogging torque of CPM, and it can be seen that with structures changes, the torque ability of CPM can be improved as well. In this paper, the design issues for the CPM were presented.…”

Mitigation of cogging torque in TFPM machines with flux concentrators and evaluation of the structures by using the SC method

“…Some previous attempts to reduce the cogging torque of transverse-flux permanent-magnet machines (TFPMMs) are as follows: studying the effects of skewing the rotor core and optimising the rotor and stator cores on the cogging torque [11]; varying the stator tooth span to reduce cogging torque [12]; assessing the effects of teeth geometry (herringbone teeth) on a TFPM using the three-dimensional finite element method (3D-FEM) [13]; adding notches on both the stators and rotors (PMs) of a dual air-gap TFPM [14]; surveying the various types of techniques for reducing cogging torque in claw-pole motors [15]; exploring the effect of ordered and disordered stator yokes distance on cogging torque [16]; and reducing cogging torque and increasing efficiency through the Taguchi method for design optimisation [17].…”

Cogging Torque Reduction Based on a New Pre-Slot Technique for a Small Wind Generator

“…However, machines based on permanent magnets (PMs) also have some drawbacks, and the cogging torque is one of the main ones. The magnetic interaction between the flux generated by the rotor PMs and the stator geometry results in a pulsating torque called cogging torque, which, depending on the PM machine design, can cause an undesired ripple in both the machine's induced voltage (EMF) and its mechanical torque [7,8]. Other problems with PMSGs are the vibrations and noise they make.…”