Exciter circuit for an externally excited synchronous machine, motor vehicle and method for de-excitation of an exciter winding

A motor vehicle, comprising:

• an externally excited synchronous machine;
• an exciter circuit associated with the externally excited synchronous machine, wherein the exciter circuit includes:
• two voltage supply terminals for a voltage supply;
• two exciter current terminals configured to be connected to an exciter winding of the externally excited synchronous machine;
• a bridge circuit coupled to the voltage supply terminals,
• a controller;
• and
• a protective arrangement at a side of the exciter circuit with the exciter current terminals, wherein the protective arrangement includes a semiconductor switch electrically connected in series with the exciter winding, and a freewheeling path electrically connected in parallel with the exciter winding
• wherein the freewheeling path includes a connection point between one of the exciter current terminals and the semiconductor switch,
• wherein the freewheeling path includes;
• a freewheeling diode which, in operation, is blocking in an exciter current flow direction;
• and
• a conversion resistor electrically connected in series with the freewheeling diode,
• wherein the bridge circuit includes a bridge switch electrically connected in series with a bridge diode,
• wherein a first end of the semiconductor switch is electrically connected between the bridge switch and the bridge diode, and a second end of the semiconductor switch is electrically connected to the connection point of the freewheeling path, and
• wherein the controller, in operation, opens the semiconductor switch when a de-excitation signal is present;
• and
• a power electronics arrangement coupled to a voltage network.

A method for de-excitation of an exciter winding of an externally excited synchronous machine, the method comprising:

• providing an exciter circuit, wherein the exciter circuit includes:
• two voltage supply terminals for a voltage supply;
• two exciter current terminals configured to be connected to an exciter winding of the externally excited synchronous machine;
• a bridge circuit coupled to the voltage supply terminals,
• a controller;
• and
• a protective arrangement at side of the exciter circuit with the exciter current terminals, wherein the protective arrangement includes a semiconductor switch electrically connected in series with the exciter winding and a freewheeling path running in parallel with the exciter winding, and having
• wherein the freewheeling path includes:
• a connection point between one of the exciter current terminals and the semiconductor switch,
• wherein the freewheeling path includes:
• a freewheeling diode which, in operation, is blocking in an exciter current flow direction;
• and
• a conversion resistor electrically connected in series with the freewheeling diode;
• and
• wherein the bridge circuit includes a bridge switch electrically connected in series with a bridge diode, and
• wherein a first end of the semiconductor switch is electrically connected between the bridge switch and the bridge diode, and a second end of the semiconductor switch is electrically connected to the connection point of the freewheeling path, and
• opening, by the controller, the semiconductor switch when a de-excitation signal is present.