Effect of magnetic properties on performance of electrical machines with ferrite magnets

Abstract

The increased focus on ferrite magnets makes it interesting to investigate their suitability in electrical machines such as generators for wind power and motors for electric cars. Efforts are currently being made to improve the magnetic properties of ferrites. A simulation method is used to investigate how different magnetic properties such as remanence, coercivity and intrinsic coercivity affect the performance of electrical machines, here quantified as output torque. It is also ensured that the magnet is not partly demagnetized during a short-circuit event. Simulations are performed through a two-dimensional finite-element-based simulation method. Not all combinations of magnetic properties will render a usable design and it is therefore investigated how high the required values are for different magnetic properties as well as how high an output torque can be achieved. It is concluded that increasing the remanence or the coercivity can be quantified as an improved energy product, whereas improvement of the intrinsic coercivity enables the magnet to have a more optimal shape and thereby have a working point where the energy product is maximized. In addition it is found that for a fixed available magnetic energy, the performance does not change significantly with increasing remanence.