A new motor has been developed that combines the goals of greater compactness, increased power and a quiet drive. This motor is an interior permanent magnet synchronous motor (IPM motor) that combines an interior permanent magnet rotor and a stator with concentrated windings.
In addition, development of the motor focused on the slot combination, the shape of the magnetic circuits and the control method all designed to reduce motor noise and vibration.
An 8-pole rotor, 12-slot stator combination was employed, and a gradually enlarged air gap configuration was used in the magnetic circuits. The gradually enlarged air gap brings the centers of the rotor and the stator out of alignment, changing the curvature, and continually changing the amount of air gap as the rotor rotates. The use of the gradually enlarged air gap brings torque degradation to a minimum, and significantly reduces torque fluctuation and iron loss of rotor and stator.
A superposed harmonic current is used as the control method for the motor. This control method reduces torque fluctuation by adding a harmonic current component on the motor drive control in order to cancel the peaks of the torque waveform.
The application of the newly developed three motors in the SPORT HYBRID SH-AWD reduced cogging torque by 50% and torque fluctuation by 50% at an average torque of 5 Nm. The noise and vibration were reduced by at least 12 dB. This technology made it possible to realize quiet motor operation.
