A dual-motor drive system for scraper conveyor

Current scraper conveyors with permanent magnet synchronous motors often improve their efficiency by updating the mechanical structure of their drive systems, few efforts are made to optimize the control of permanent magnet synchronous motors. This paper fills the gap by involving maximum torque per ampere (MTPA) and flux-weakening controls to improve the dual-motor drive system of scraper conveyors. Given the direct-axis current, the proposed system reduces the motor loss by adopting MTPA control to obtain the maximum torque per ampere. By using flux-weakening control to increase the speed regulation range of scraper conveyors, the coal output of a scraper conveyor can be relatively stable under various production loads. To balance the power of two motors, the proposed system applies the master-slave control that takes the rear motor as the master and the front motor as the slave, and gives the master's torque setpoint to the slave's MTPA and flux-weakening control systems. The effectiveness of the proposed system is evaluated by using AMEsim and Matlab/Simulink to simulate the scraper conveyor and its dual-motor drive system, respectively. The results show that the stator current under MTPA can be stable at 130.1 A when the motor load suddenly raised, while the stator current under traditional vector control is stable at 149.2 A. MTPA control outperforms the vector control, as the smaller stator current implies the better system when the same output torque maintained. Flux-weakening control extends the speed regulation range from 0-750 r/min to 0-850 r/min. Master-slave control maintains the same output torques of the master and the slave, leading to the balanced dual-motor power.