Comparative Study of 3-Phase Permanent Magnet Brushless Machines with Concentrated, Distributed and Modular Windings

The paper compares the merits of permanent magnet brushless machines equipped with concentrated, distributed and modular stator windings for servo applications. Analytical expressions for predicting the open-circuit and armature reaction magnetic field distributions in a modular wound machine are established and utilized to provide an effective tool for design optimisation. All three machines are optimally designed to meet the same performance specification and thermal behaviour. In order to compare the noise and vibration characteristics of the different machines, the distribution of their radial force density waveforms is analysed and quantified. It is shown that the modular wound machine has the highest efficiency and the lowest torque ripple. However, it also contains low and high order stator mmf space harmonics, which induce additional eddy currents in the magnets and may excite low frequency modes of vibration.