Abstract: Aiming at the problems of high power consumption, high demagnetization risk, and narrow speed regulation range of permanent magnet motor for top-driving drilling system, a novel direct-drive variable frequency top drive system with hybrid permanent magnet memory machine (HPM-MM) as the core is proposed. According to the corresponding relationship between permanent magnet flux linkage and speed under different magnetization states of HPM-MM, combined with the coordinated control of online written pole and leading angle magnetic weakening, a zoning speed control strategy is realized. In addition to the excellent characteristics of a permanent magnet synchronous motor, a wide range of smooth speed regulation characteristics is available in the HPM-MM system. By calculating the turning speed, the operation area is divided into constant torque low-speed area and constant power high-speed area. In the low-speed region, the motor is in the forward saturation magnetization state, so as to obtain the maximum output torque. The high-speed area includes weak magnetic field Ⅰ area and weak magnetic field Ⅱ areas, where the former realize high-efficiency speed regulation through backward magnetization state adjustment of soft magnetic material, and the latter adopts the leading angle flux weakening control to further widen the speed regulation range by redistributing the stator current.

Key words: vernier motor, hybrid permanent magnet excitation, magnetic regulation, leading angle flux-weakening, speed control