On application of fractional single-toothed concentrated windings in synchronous machines with permanent magnets

Abstract

Some properties of fractional single-toothed concentrated windings that contribute to their effective application in electrical machines have been considered. Small end windings allow making an electrical machine more compact in the axial direction, which makes it possible to use it in several applications: in motor-wheel drives, in a wind wheel power generator, in an elevator drive without room for a machine, etc. Fractional windings can significantly reduce the cogging torque of an electrical machine. This reduces the cogging torque, which is very important in wind energy, but at the same time it increases the smoothness and accuracy of positioning, which allows it to be used in special electrical machines. One of the drawbacks of the fractional single-toothed concentrated windings is a worse MMF harmonic content. With this in mind, application of a two-layer winding is to be preferred to that of a single-layer one. An example shows application of a fractional tooth concentrated winding in a synchronous engine with permanent magnets to drive the plunger pump used for oil production. The use of a two-layer winding instead of a single-layer one allowed reducing the eddy-current losses in the rotor by 3.7 times and avoiding unacceptable overheating of magnets.