Minimizing cogging torque in permanent magnet synchronous generators for small wind turbine applications

Abstract

Permanent magnet synchronous generators have a wide usage among electric machines, especially in small wind turbine systems. However permanent magnet synchronous generators suffer from cogging torque due to the magnetic interaction between the poles of the rotor’s permanent magnets and the steel laminations of the stator’s teeth. The cogging torque drawback is a major problem in this kind of generators that affects its functionality negatively. In the literature many different approaches for reducing the cogging torque are proposed and each different approach achieves different amount of reduction in the cogging torque. In this study 6 different cogging torque reduction techniques are considered and with finite element simulations using the JMAG simulation software, they are compared with each other in terms of percent reduction in the cogging torque. Present simulations show that among the considered different approaches, continuous skewing technique reduces the cogging torque the most with respect to the each other techniques considered. Also using the step skewing of the rotor or stator, changing the slot opening width and having dummy slots techniques can decrease the cogging torque more or less the same amount in magnitude. Present results indicate that changing the radial shoe depth technique has almost no effect in reducing the cogging torque.