System and method for fast discharge of a ring motor field

An apparatus for discharging electromagnetic energy from a field winding of a synchronous motor, wherein the field winding is energized by a direct current source comprising a direct current link capacitor, the apparatus comprising:

• means for receiving a fault signal indicating that a short circuit of the direct current link capacitor has occurred;
• means for controlling one or more switches of a field discharge system to transfer the electromagnetic energy from the field winding to an ultracapacitor in response to the fault signal;
• means for storing the electromagnetic energy in the ultracapacitor;
• means for measuring a field current flowing through the field winding;
• and
• means for stopping transfer of the electromagnetic energy to the ultracapacitor when the field current is less than or equal to a threshold value.

A non-transitory computer readable medium storing computer program instructions for discharging electromagnetic energy from a field winding of a synchronous motor, wherein the field winding is energized by a direct current source comprising a direct current link capacitor, the computer program instructions defining the steps of:

• receiving a fault signal indicating that a short circuit of the direct current link capacitor has occurred;
• in response to the fault signal, transferring, by one or more switches of a field discharge system, the electromagnetic energy from the field winding to an ultracapacitor;
• storing the electromagnetic energy in the ultracapacitor;
• wherein the computer program instructions further comprise computer program instructions defining the steps of:
• measuring a field current flowing through the field winding;
• and
• stopping transfer of the electromagnetic energy to the ultracapacitor when the field current is less than or equal to a threshold value.

A field discharge system for transferring electromagnetic energy from a field winding of a synchronous motor, wherein the field winding is energized by a direct current source comprising a direct current link capacitor, the field discharge system comprising:

• an ultracapacitor;
• a first switch operatively coupled to the ultracapacitor;
• a second switch operatively coupled to the ultracapacitor;
• a control element configured to transmit a fault signal in response to a short circuit of the direct current link capacitor;
• and
• a field discharge system controller operatively coupled to the first switch, the second switch, and the control element;
• wherein:
• the field discharge system controller is configured to:
• transmit a first control signal;
• and
• in response to receiving a fault signal from the control element, transmit a second control signal;
• and the first switch and the second switch are configured to:
• in response to receiving the first control signal from the field discharge system controller, transmit current from the direct current source through the field winding;
• and
• in response to receiving the second control signal from the field discharge system controller, transfer electromagnetic energy from the field winding to the ultracapacitor and store the electromagnetic energy in the ultracapacitor.