Magnetically geared systems and methods

A method of operating a system, the system comprising:

• a stator comprising a plurality of windings configured to generate a rotating magnetic field;
• a first rotor comprising a plurality of permanent magnets having an associated second magnetic field;
• and
• a second rotor through which the rotating magnetic field and the second magnetic field are coupled, whereby rotation of the first rotor is magnetically coupled to rotation of the second rotor;
• wherein one of the first rotor and the second rotor is a drive rotor configured for attachment to an external load, and the other of the first rotor and the second rotor is a passive rotor,
• the method comprising:
• determining one of a angular position and a rotational speed of the first rotor;
• determining one of a angular position and a rotational speed of the second rotor;
• and
• controlling a current supplied to the windings based on the determined angular position or rotational speed of the first rotor, and based on the determined angular position or rotational speed of the second rotor.

A system comprising:

• a stator comprising a plurality of windings configured to generate a rotating magnetic field;
• a first rotor comprising a plurality of permanent magnets having an associated second magnetic field;
• a second rotor through which the rotating magnetic field and the second magnetic field are coupled, whereby rotation of the first rotor is magnetically coupled to rotation of the second rotor;
• a rotational sensor associated with the second rotor and configured to detect a rotational position of the second rotor;
• and
• a controller configured to:
• calculate an electromagnetic torque in the system, based on a magnitude of a current supplied to the windings;
• calculate an estimated load angle of the system based on the electromagnetic torque and a known maximum torque capacity of the system;
• calculate a theoretical first rotor position based on the detected second rotor position and a known gear ratio of the system;
• and
• control a phase of the current supplied to the windings such that the rotating magnetic field is offset from an electrical angle associated with the theoretical first rotor position by the estimated load angle.

A method of operating a system,

• the system comprising:
• a stator comprising a plurality of windings configured to generate a rotating magnetic field;
• a first rotor comprising a plurality of permanent magnets having an associated second magnetic field;
• a second rotor through which the rotating magnetic field and the second magnetic field are coupled, whereby rotation of the first rotor is magnetically coupled to rotation of the second rotor;
• and
• a rotational sensor associated with the second rotor and configured to detect a rotational position of the second rotor;
• and the method comprising:
• calculating an electromagnetic torque in the system, based on a magnitude of a current supplied to the windings;
• calculating an estimated load angle of the system based on the electromagnetic torque and a known maximum torque capacity of the system;
• calculating a theoretical first rotor position based on the detected second rotor position and a known gear ratio of the system;
• and
• controlling a phase of the current supplied to the windings such that the rotating magnetic field is offset from an electrical angle associated with the theoretical first rotor position by the estimated load angle.