An auxiliary winding for use in an engine-driven generator system is disclosed. The auxiliary winding is separate from but resides with the main winding in the stator slots of an alternator in the generator system. The auxiliary winding is configured to utilize the fundamental component of the flux in the airgap of the alternator along with selected spatial harmonic components to provide power to an automatic voltage regulator during all operating conditions.

A self-excitation system for a locomotive having at least a primary mover is provided. The self-excitation system may include a traction alternator, a permanent magnet machine, and a chopper circuit. The traction alternator may include an alternator stator and an alternator rotor mechanically coupled to a drive shaft of the primary mover. The permanent magnet machine may include a machine stator and a machine rotor mechanically coupled to the drive shaft. The chopper circuit may be configured to receive electrical signals from the machine stator and control a field excitation of the traction alternator.

A self-excitation system for a locomotive having at least a primary mover is provided. The self-excitation system may include a traction alternator, a permanent magnet machine, and a chopper circuit. The traction alternator may include an alternator stator and an alternator rotor mechanically coupled to a drive shaft of the primary mover. The permanent magnet machine may include a machine stator and a machine rotor mechanically coupled to the drive shaft. The chopper circuit may be configured to receive electrical signals from the machine stator and control a field excitation of the traction alternator.

A field winding synchronous machine drive system includes a field winding synchronous machine having a stator and a rotor and a drive apparatus configured to drive the field winding synchronous machine. The stator has N m-phase stator coils wound on a stator core to create a rotating magnetic field, where N is an integer not less than 2 and m is an integer not less than 3. The rotor has at least one main field winding wound on a rotor core to create field magnetic flux. The drive apparatus includes N inverters each of which supplies m-phase alternating current to a corresponding one of the N m-phase stator coils. Specifically, each of the inverters supplies the corresponding m-phase stator coil with the m-phase alternating current which includes a fundamental-wave current and a time-harmonic current superimposed on the fundamental-wave current; the time-harmonic current has a shorter period than the fundamental-wave current.

A variable speed generator for producing AC electrical power includes an alternator powerable by rotational action to generate a first AC current, and a first rectifier which rectifies the first AC current from the alternator. The generator further includes a main exciter having a first field winding which receives the rectified first AC current, and having a first armature which produces in response a second AC current. The generator further includes a second rectifier which rectifies the second AC current from the first armature. The generator further includes a main generator having a second field winding which receives the rectified second AC current, and having a second armature which produces in response an output AC current. The second field winding is configured to provide a plurality of selectively activatable pole configurations which differ in the number of their poles, such that the frequency of the output AC current can be varied by switching between the pole configurations. The variable speed generator further includes a control arrangement for activating the selected pole configuration.