An apparatus having a first set of windings disposed about a first main leg of a transformer core, and a second set of windings disposed about a second main leg of the transformer core. The first set of windings are electrically coupled to the second set of windings to selectively provide a parallel connection and a series connection between the first set of windings and the second set of windings. Additionally, at least two windings of the first set of windings are electrically coupled to each other to selectively provide a parallel connection and a serial connection between the at least two windings of the first set of windings. Similarly, two windings of the second set of windings are electrically coupled to each other to selectively provide a parallel connection and a serial connection between the at least two windings of the second set of windings.

An electrical machine system, including: an electrically excited synchronous machine including a stator having a plurality of stator windings, and a rotor having a plurality of rotor windings, a transformer including a stationary primary winding and a secondary winding arranged on the rotor; wherein the electrically excited synchronous machine further includes a voltage pulse width modulator configured to receive a control signal used to control the field currents of the rotor windings; wherein the electrical machine system further includes an inverter connected to the stator and configured to supply phase currents to the stator windings; and wherein the inverter is further configured to provide the control signal to the voltage pulse width modulator.

An electrical machine system, including: an electrically excited synchronous machine including a stator having a plurality of stator windings, and a rotor having a plurality of rotor windings, a transformer including a stationary primary winding and a secondary winding arranged on the rotor; wherein the electrically excited synchronous machine further includes a voltage pulse width modulator configured to receive a control signal used to control the field currents of the rotor windings; wherein the electrical machine system further includes an inverter connected to the stator and configured to supply phase currents to the stator windings; and wherein the inverter is further configured to provide the control signal to the voltage pulse width modulator.