System and Method for Determining Position of Hall Sensors Relative to the Stator Winding of Brushless DC or Synchronous AC Permanent Magnet Motor

Reference#: P02710

Multi-phase electric power is a common method for providing alternating current for power generation, transmission, and distribution. For a particular phase, the alternating currents of the other two phases are shifted in time by one-third and two-thirds of a cycle, respectively. The differing of the phases of the three alternating currents enables constant transfer of power to a load. Multi-phase electric power provides efficient transfer of power to multi-phase motors. In general, a multi-phase motor includes a stator (i.e., stationary portion) and multiple rotors (i.e., rotating portion) or includes multiple stators and a rotor. Multi-phase electrical power applied to a multi-phase motor results in current flow traversing the multiple stators of the motor. The current flow traversing the multiple stators results in a magnetic field, which produces magnetic torque on the rotor. The magnetic torque applied to the rotor results in rotation of the rotor. Some conventional multi-phase motor implementations use rotor location information received from sensors for generating necessary signals for controlling multi-phase motors. Other conventional multi-phase motor implementations use detection of zero voltage crossing points associated with Back Electromotive Force (BEMF).

Researchers at the Johns Hopkins Applied Physics Laboratory have developed a method for monitoring a motor having a stator, a rotor, and a detector. The stator can receive a driving signal to produce an initial magnetic field. The rotor can rotate in a circle relative to the stator. The rotor has a magnetic portion that can emit a second magnetic field in a radial direction. The detector can output a detection signal based on the position of the rotor.

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