Efficiency improvement method for low output of Multi Coils Motor

There are various approaches to improve the efficiency of Permanent Magnetic Synchronous Motor (PMSM). Among them, vector control is often used. Focusing on the efficiency at low output, there is a limit to the improvement of efficiency only by vector control. Losses in the motor include "Iron Loss", "Copper Loss", "Mechanical Loss", and "Circuit Loss". Among them, "Circuit Loss (mainly switching loss)" exists even with low output. This paper proposes a method of improving the efficiency of Multi-Coils Motor (MCM) when its output is low. By designing the transfer function of Delta Sigma Modulation (DSM) to be stable, the amplitude inside the modulator is reduced and by suppressing the fluctuation of the output from quantizer, switching times can be reduced and that leads to reduce losses. Furthermore by reducing the number of coils to be driven when the output is low, the number of switching times is reduced and loss is reduced. Simulation of MATLAB/Simulink shows stabilizing DSM reduces the number of switching times. In addition, the result of measuring an actual machine shows that improve the efficiency when output of MCM is low.