Automatic fault current protection for a locomotive propulsion system

Claim 1

A fault current protection system for a traction vehicle propulsion system including at least one electric traction motor, a synchronous generator having armature and field windings, a controllable source of excitation current connected to the field windings, and electric power conditioning means interconnecting the armature windings of the generator to the at least one traction motor, the protection system comprising: detection means for producing a fault signal in response to a current from said armature windings in excess of a preselected current value; a capacitor; a solid-state controllable electric switching means connected in series circuit with said capacitor, said switching means having both turned-on and turned-off states and being normally turned off, said switching means and said capacitor being connected in parallel circuit arrangement with the field winding of the generator; means for charging said capacitor to a voltage sufficient to commutate off the controllable source of field excitation current; and means coupling said fault signal to said electric switching means for turning on said switching means for coupling said capacitor in parallel with the controllable source of field excitation current in response thereto, whereby said capacitor discharges through the field winding while concurrently commutating off the field current excitation source.

Claim 13

A method for protecting a traction vehicle propulsion system from fault currents, the propulsion system including at least one traction motor, a synchronous generator having armature and field windings, a controllable source of excitation current connected to the field windings, electric power conditioning means interconnecting the armature windings of the generator to the at least one traction motor, and current sensing means for providing data representative of the magnitude of instantaneous armature winding current, the method comprising the steps of: detecting a fault current from the armature windings and producing a fault signal in response thereto; coupling, in response to the fault signal, pre-charged capacitance means in parallel with the field winding, the capacitance means being pre-charged to a voltage greater than a maximum field winding operating voltage whereby current to the field windings becomes supplied by the capacitance means and the controllable source of electric current becomes commutated off; and inserting, subsequent to the step of coupling, resistance means in circuit with the field windings and the capacitance means whereby energy in the field windings is dissipated in the resistance means.

Claim 14

A method for protecting a traction vehicle propulsion system from fault currents, the propulsion system including at least one traction motor, a synchronous generator having armature and field windings, a controllable source of excitation current connected to the field windings, electric power conditioning means interconnecting the armature windings of the generator to the at least one traction motor, and current sensing means for providing data representative of the magnitude of instantaneous armature winding current, the method comprising the steps of: detecting a fault current from the armature windings and producing a fault signal in response thereto; coupling, in response to the fault signal, pre-charged capacitance means in parallel with the field winding, the capacitance means being pre-charged to a voltage greater than a maximum field winding operating voltage whereby current to the field windings becomes supplied by the capacitance means and the controllable source of electric current becomes commutated off; and inserting, subsequent to the step of coupling, resistance means in circuit with the field windings and the capacitance means whereby energy in the field windings is dissipated in the resistance means.