(under subclass 717) Subject matter wherein a rotating magnetic field from an alternating current winding and rotating rotor induce a voltage in the field winding includes a switching circuit under the control of the induced voltage to control direct current to the field winding.
(1) Note. Subject matter of this subclass type includes, for example, relay and electronic switching circuits.
(2) Note. Subject matter classified in this subclass may include a armature or alternating current winding, but will not include circuits connected to the armature winding. See subclass 700 for synchronous motors with circuits connected to the field and the alternating current winding when the energized motor is in the running mode but not being started.
(3) Note. Subject matter of this subclass type includes, for example, brushless motor solid-state switching device circuits to control the application of direct current to the field winding after the motor is near synchronous speed.
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459, for general motor control means responsive to terminal voltage or counterelectromotive force of the controlled motor.
