Electrical machines with reduced cogging

摘要

The present invention provides an electrical machine (1) with reduced cogging. The magnet poles (3) of the electrical machine are comprised of at least two separate groups of at least two circumferentially adjacent magnet poles. One of the circumferentially outer magnet poles (3a, 3h) in one of the groups of magnet poles is defined as being in its reference position. The reference position of each other magnet pole (3b to 3g) is defined as the position each other magnet pole would occupy if all the magnet poles were equally circumferentially spaced around the first or second body and the one circumferentially outer pole was in its reference position. At least one of the circumferentially outer magnet poles (3a, 3h) in each group is sited in its reference position. At least one magnet pole (3a to 3g) in each group is a displaced magnet pole and is sited in a position that is displaced from its reference position by an amount that is not equal to an integral multiple of the reference angular pitch of the winding slots. The displacement of the magnet poles (3) provides a pronounced reduction in cogging.