다상 전동기 설계 및 특성 해석에 관한 연구

Abstract

Before 1980s the propulsion system for submarines were driven by DC motors using storage batteries as their power resource. Since then, PMPM (Permanent Magnet Propulsion Motor) was developed with a unified structure consisting of an inverter and motor together. This structure has a number of advantages compared with DC motors. In particular it is smaller, takes up less space and has a greater power output.

Recently, It is needed for submarines to have bigger spaces and speedy characteristics so that the PMPM is required to have greater power per unit volume. The 'multi-phase motor' is believed to be the best PMPM to meet the needs of modern submarines. This paper proposes the use of the ‘multi-phase electric’ motor which has an independent-connected structure and uses an H-bridge inverter. The multi-phase electric motor has more than 3 phases and its phases are individualized.

To analyze its specific characteristics mentioned above, I compared simulations by using several motors (Y-connected 3, 7 phase BLDC motors and independent connected 3 phase BLDC motor). As a result, it is found that torque pulsation of Y-connected 7 phase BLDC motor was reduced more than 3 phase motor. In addition to it, comparing the simulation between Y-connected 3 phase BLDC motor and independent-connected 3 phase BLDC motor, phase-voltage of independent-connected 3 phase was increased in a same condition.

It was also found that the phase voltages of the independent connected 3 phase BLDC motor were increased. When the stator resistance and inductance are stable, phase voltage increases maximum torque. Thus the independent multi-phase BLDC motor has the specific characteristics of reduced torque pulsation and high maximum torque compared to the 3 phase BLDC motor.

In conclusion that the multi-phase motor has the characteristics of reduced torque pulsation and higher torque output by analyzing control characteristics of multi-phase propulsion motor and H-bridge inverter. Additionally, suitable control for submarines has been found with the multi-phase motor by using current control algorithm to produce reduced torque pulsation in the commutation period. For practical purpose, additional experiment-based research and development of the control algorithm for commutating of the multi-phase motor is required.