Ground fault voltage limiting for a locomotive electric traction motor

Claim 2

For a locomotive system wherein operating voltage is supplied to the locomotive traction motor in accordance with operator demand up to a voltage limit having a maximum value determined in relation to the motor design limits, and wherein the motor voltage supply is temporarily interrupted in response to the sensing of a motor ground fault and permanently interrupted after a number of such temporary interruptions, apparatus for preventing a permanent interruption of motor voltage due to moisture induced ground faulting, comprising: limit setting means effective in response to each sensing of a ground fault for reducing said voltage limit to a level determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault, and further effective following each of said temporary interruptions of motor voltage supply for incrementing the voltage limit toward said maximum value whenever the motor is continuously operated for a second predetermined time interval with no ground faults, whereby when the sensed ground fault is moisture induced, the voltage limit reductions permit continued motor operation following the temporary interruption of motor voltage, and the voltage limit is returned to said maximum value as the heat generated by such continued motor operation dries the moisture which induced the ground fault.

Claim 3

Apparatus as set forth in Claim 1, wherein said limit setting means is effective in the event a ground fault occurs after the voltage limit is reduced to a reference low value in response to one or more sensed ground faults for preventing incrementing of the voltage limit until it is determined that corrective action has been attempted by the locomotive operator.

Claim 4

Apparatus as set forth in Claim 2, wherein said limit setting means is further effective after it is determined that corrective action has been attempted by the locomotive operator for increasing the voltage limit to said maximum value.

Claim 5

For a locomotive system including a motor voltage controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a predetermined time interval in response thereto, and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, the improvement comprising: limit setting means for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, said limit setting means being (1) effective in response to each sensing of a ground fault by said motor voltage controller for reducing said voltage limit to a value substantially less than the voltage supplied to said motor just prior to the occurrence of the ground fault to thereby reduce the motor operating voltage to a value sufficiently low to permit continued motor operation following the temporary interruptions of motor voltage by said motor voltage controller when the sensed ground faulting is moisture induced; (2) effective following each of said temporary interruptions of motor voltage supply for incrementing the voltage limit toward said maximum value by a reference amount for each specified period of motor operation under a reduced voltage limit for which no ground faults occur to thereby progressively return the motor operating voltage to said maximum value as the heat generated by the motor operation dries the moisture which induced the ground faulting; and (3) effective in response to the sensing of a ground fault after an incrementing of the voltage limit toward the maximum value for decrementing the voltage limit by said reference amount to thereby permit continued motor operation and continued drying of the moisture following the temporary interruption of motor voltage by said motor voltage controller.

Claim 6

For a locomotive system including a motor voltage controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a predetermined time interval in response thereto, and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, the improvement comprising: limit setting means for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, said limit setting means being (1) effective in response to each sensing of a ground fault by said motor voltage controller for reducing said voltage limit to a value substantially less than the voltage supplied to said motor just prior to the occurrence of the ground fault to thereby reduce the motor operating voltage to a value sufficiently low to permit continued motor operation following the temporary interruptions of motor voltage by said motor voltage controller when the sensed ground faulting is moisture induced; (2) effective following each of said temporary interruptions of motor voltage supply for incrementing the voltage limit toward said maximum value by a reference amount for each specified period of motor operation under a reduced voltage limit for which no ground faults occur to thereby progressively return the motor operating voltage to said maximum value as the heat generated by the motor operation dries the moisture which induced the ground faulting; and (3) effective in response to the sensing of a ground fault after an incrementing of the voltage limit toward the maximum value for decrementing the voltage limit by said reference amount to thereby permit continued motor operation and continued drying of the moisture following the temporary interruption of motor voltage by said motor voltage controller.

Claim 7

The improvement set forth in Claim 4, wherein said limit setting means is further effective upon decrementing said voltage limit to permit continued motor operation and continued drying of the moisture for establishing a mode of operation wherein further ground faulting causes the voltage limit to be reduced to a predetermined minimum value, and wherein further incrementing of the voltage limit is prevented until it is determined that corrective action has been attempted by the locomotive operator.

Claim 8

For a locomotive system including a motor voltage controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a first predetermined time interval in response thereto and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, the improvement comprising: limit setting means for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, said limit setting means being effective in response to each sensing of a ground fault by said motor voltage controller for reducing said voltage limit to a value determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault to thereby reduce the motor operating voltage to a value sufficiently low to permit continued motor operation following the temporary interruption of motor voltage by said motor voltage controller when the sensed ground faulting is moisture induced, and further effective following each of said temporary interruptions of motor voltage supply for incrementing the voltage limit toward said maximum value by a reference amount for each relatively short predetermined interval during which said motor operates at a voltage substantially as great as said voltage limit with no ground faulting, and for returning the voltage limit to said maximum value if said motor is cumulatively operated at any voltage for a relatively long predetermined interval with no ground faulting, whereby the motor operating voltage is returned to said maximum value as the heat generated by the motor operation dries the moisture which induced the ground faulting.

Claim 9

For a locomotive system including a motor voltage controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a first predetermined time interval in response thereto and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, the improvement comprising: limit setting means for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, said limit setting means being effective in response to each sensing of a ground fault by said motor voltage controller for reducing said voltage limit to a value determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault to thereby reduce the motor operating voltage to a value sufficiently low to permit continued motor operation following the temporary interruption of motor voltage by said motor voltage controller when the sensed ground faulting is moisture induced, and further effective following each of said temporary interruptions of motor voltage supply for incrementing the voltage limit toward said maximum value by a reference amount for each relatively short predetermined interval during which said motor operates at a voltage substantially as great as said voltage limit with no ground faulting, and for returning the voltage limit to said maximum value if said motor is cumulatively operated at any voltage for a relatively long predetermined interval with no ground faulting, whereby the motor operating voltage is returned to said maximum value as the heat generated by the motor operation dries the moisture which induced the ground faulting.

Claim 10

For a locomotive system wherein operating voltage is supplied to the locomotive traction motor in accordance with operator demand up to a voltage limit having a maximum value determined in relation to the motor design limits, and wherein the motor voltage supply is temporarily interrupted in response to the sensing of a motor ground fault and permanently interrupted after a number of such temporary interruptions, a method of operation for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, comprising the steps of: reducing said voltage limit in response to the sensing of a ground fault to a level determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault; and incrementing the voltage limit toward said maximum value following each of said temporary interruptions of motor voltage supply whenever the motor is continuously operated for a second predetermined time interval with no ground faults, whereby when the sensed ground fault is moisture induced, the voltage limit reductions permit continued motor operation following the temporary interruption of motor voltage, and the voltage limit is returned to said maximum value as the heat generated by such continued motor operation dries the moisture which induced the ground fault.

Claim 11

For a locomotive system wherein operating voltage is supplied to the locomotive traction motor in accordance with operator demand up to a voltage limit having a maximum value determined in relation to the motor design limits, and wherein the motor voltage supply is temporarily interrupted in response to the sensing of a motor ground fault and permanently interrupted after a number of such temporary interruptions, a method of operation for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, comprising the steps of: reducing said voltage limit in response to the sensing of a ground fault to a level determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault; and incrementing the voltage limit toward said maximum value following each of said temporary interruptions of motor voltage supply whenever the motor is continuously operated for a second predetermined time interval with no ground faults, whereby when the sensed ground fault is moisture induced, the voltage limit reductions permit continued motor operation following the temporary interruption of motor voltage, and the voltage limit is returned to said maximum value as the heat generated by such continued motor operation dries the moisture which induced the ground fault.

Claim 12

The method as set forth in Claim 7, including the step of: preventing the incrementing of the voltage limit until it is determined that corrective action has been taken by the locomotive operator in the event a ground fault occurs after the voltage limit has been reduced to a predetermined minimum value in response to one or more sensed ground faults.

Claim 13

For a locomotive system including a motor voltage controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a predetermined time interval in response thereto, and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, a method of operation for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, comprising the steps of: reducing said voltage limit in response to each sensing of a ground fault by said motor voltage controller to a value substantially less than that supplied to said motor just prior to the occurrence of the ground fault to thereby reduce the motor operating voltage to a value sufficiently low to permit continued motor operation following the temporary interruption of motor voltage by said motor voltage controller when the sensed ground faulting is moisture induced; incrementing the voltage limit toward said maximum value by a reference amount following each of said temporary interruptions of motor voltage supply for each specified period of motor operation under a reduced voltage limit for which no ground faults occur to thereby progressively return the motor operating voltage to said maximum value as the heat generated by the motor operation dries the moisture which induced the ground faulting; and decrementing the voltage limit by said reference amount in response to the sensing of a ground fault after an incrementing of the voltage limit toward said maximum value to thereby permit continued motor operation and continued drying of the moisture following the temporary interruption of motor voltage by said motor voltage controller.

Claim 14

For a locomotive system including a motor voltage controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a predetermined time interval in response thereto, and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, a method of operation for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, comprising the steps of: reducing said voltage limit in response to each sensing of a ground fault by said motor voltage controller to a value substantially less than that supplied to said motor just prior to the occurrence of the ground fault to thereby reduce the motor operating voltage to a value sufficiently low to permit continued motor operation following the temporary interruption of motor voltage by said motor voltage controller when the sensed ground faulting is moisture induced; incrementing the voltage limit toward said maximum value by a reference amount following each of said temporary interruptions of motor voltage supply for each specified period of motor operation under a reduced voltage limit for which no ground faults occur to thereby progressively return the motor operating voltage to said maximum value as the heat generated by the motor operation dries the moisture which induced the ground faulting; and decrementing the voltage limit by said reference amount in response to the sensing of a ground fault after an incrementing of the voltage limit toward said maximum value to thereby permit continued motor operation and continued drying of the moisture following the temporary interruption of motor voltage by said motor voltage controller.

Claim 15

For a locomotive system including a controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a predetermined time interval in response thereto, and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, a method of operation for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, comprising the steps of: reducing said voltage limit in response to the sensing of a ground fault by said controller to a level determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault; incrementing the voltage limit toward said maximum value following each of said temporary interruptions of motor voltage supply for each relatively short predetermined interval during which said motor operates at a voltage substantially as great as said voltage limit with no ground faulting; and returning the voltage limit to said maximum value when the motor is operated for a relatively long predetermined interval at any voltage with no ground faulting, whereby when the sensed ground fault is moisture induced, the voltage limit reductions permit continued motor operation following the temporary interruption of motor voltage, and the voltage limit is returned to said maximum value as the heat generated by such continued motor operation dries the moisture which induced the ground fault.

Claim 16

For a locomotive system including a controller which supplies operating voltage to the locomotive traction motor in accordance with operator demand but which prevents the supplied voltage from exceeding a voltage limit having a maximum value determined in relation to the motor design limits, and which senses the occurrence of a traction motor ground fault, temporarily interrupts the motor voltage supply for a predetermined time interval in response thereto, and permanently interrupts the motor voltage supply after a number of such temporary interruptions occur within a specified time period, a method of operation for preventing the permanent interruption of motor voltage due to moisture induced ground faulting, comprising the steps of: reducing said voltage limit in response to the sensing of a ground fault by said controller to a level determined in relation to the voltage supplied to said motor just prior to the occurrence of the ground fault; incrementing the voltage limit toward said maximum value following each of said temporary interruptions of motor voltage supply for each relatively short predetermined interval during which said motor operates at a voltage substantially as great as said voltage limit with no ground faulting; and returning the voltage limit to said maximum value when the motor is operated for a relatively long predetermined interval at any voltage with no ground faulting, whereby when the sensed ground fault is moisture induced, the voltage limit reductions permit continued motor operation following the temporary interruption of motor voltage, and the voltage limit is returned to said maximum value as the heat generated by such continued motor operation dries the moisture which induced the ground fault.