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.

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.

A rotor for an electrically excited drive machine includes: a coil per rotor pole with, in each case, one first energizable coil unit, and a rotor core for holding the coils of the rotor poles. The coils have, in each case, at least one second energizable coil unit per rotor pole. The rotor has an interconnecting unit which is designed to interconnect the at least two coil units per coil in a manner which is dependent on an operating point of the electric drive machine in order to set the number of windings of the coil, and in order to electrically connect the coils of the rotor poles for configuring a rotor winding with an overall number of windings which is dependent on the numbers of windings of the coils.

A rotor for an electrically excited drive machine includes: a coil per rotor pole with, in each case, one first energizable coil unit, and a rotor core for holding the coils of the rotor poles. The coils have, in each case, at least one second energizable coil unit per rotor pole. The rotor has an interconnecting unit which is designed to interconnect the at least two coil units per coil in a manner which is dependent on an operating point of the electric drive machine in order to set the number of windings of the coil, and in order to electrically connect the coils of the rotor poles for configuring a rotor winding with an overall number of windings which is dependent on the numbers of windings of the coils.

An apparatus has a plurality of poles facing an air gap, and the poles are configured to generate a magnetic field in the air gap. The poles include a group of unchanged poles and a group of reversible poles, where a polarity of each reversible pole is configured to be changed during an operation mode, and after the polarity has been changed, each reversible pole and at least an adjacent unchanged pole in effect merged into one augmented pole, such that the pole number of the magnetic field in the air gap is changed.

An apparatus has a plurality of poles facing an air gap, and the poles are configured to generate a magnetic field in the air gap. The poles include a group of unchanged poles and a group of reversible poles, where a polarity of each reversible pole is configured to be changed during an operation mode, and after the polarity has been changed, each reversible pole and at least an adjacent unchanged pole in effect merged into one augmented pole, such that the pole number of the magnetic field in the air gap is changed.