Synthesis of cogging torque waveform from analysis of a single stator slot

A simple technique is proposed to synthesise the cogging torque waveform of a permanent magnet machine from the cogging torque which is associated with a single stator slot. An analytical expression is derived and applied to two motors, each of which has a fractional number of slots per pole. It is shown that the resultant cogging torque waveform can be synthesized to a high accuracy, as confirmed by both finite element analysis and measurements. It is also shown that not all the cogging torque harmonics which exist in the cogging torque waveform due to a single slot will be present in the resultant cogging torque, and that the most significant components can be identified analytically