Air-Cored Linear Motor: Design and Operating Behavior

Long-stator linear synchronous motors have been proven to operate efficiently at high speeds, making them suitable for ground-based high-speed transportation technologies such as Maglev trains or Hyperloop. The need for laminated steel along the track makes this type of motor cost-prohibitive which argues in favor of an ironless design. Air-cored synchronous motors are more difficult to control, especially at low speeds at the beginning of acceleration phases. Here, we report the design and low-speed performance of a long-stator air-cored linear synchronous motor. This study is based on a 4.8 m long test track with a rail-bound vehicle. Successfull motor operation with a conventional variable frequency drive system demonstrates sufficient magnetic flux linkage between an optimized multi-turn stator and a permanent magnet excitation system. We infer information from measurements for different driving profiles and air gaps from 5 mm to 25 mm. Depending on whether position and speed feedback are integrated, we observe a major difference in vibrations, leading to different levels of potential passenger comfort.