Fault detection system for electric automobile traction system having floating ground
First Claim
1. A device for detecting, in an electrically propelled automobile having a chassis, an electrical path to the chassis of the automobile from an electric traction system having a floating ground, comprising:
- a traction battery;
a traction motor;
a positive direct current (DC) line and a negative DC line interconnecting the traction battery and traction motor;
a positive sampling circuit electrically connected to the positive DC line for generating a first voltage representative of electric current flow from the battery;
a negative sampling circuit electrically connected to the negative DC line for generating a second voltage representative of electric current flow back to the battery;
an summing circuit electrically connected to the positive and negative sampling circuits for generating a summed signal representative of the first and second voltages; and
a comparator electrically connected to the summing circuit for comparing the summed signal to a first reference signal which is proportional to the traction battery voltage and outputting a fault signal in response thereto when an electrical path exists between the chassis and the traction battery.
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Accused Products
Abstract
A fault detection system detects the existence of unwanted electrical paths between the high voltage traction system of an electric car and the chassis of the car. The fault detection system includes a positive sampling RC circuit connected to the positive conductor of the traction system and a negative sampling RC circuit connected to the negative conductor of the traction system. Each RC circuit generates a voltage, and the voltages are balanced, i.e., the voltages are equal and opposite, when no leakage path exists. In contrast, when a leakage path to chassis exists, the voltages are not balanced. A comparator compares the sum of the voltages to a setpoint which varies proportionately to the varying voltage of the battery of the traction system, and a fault condition is indicated when the sum of the voltages exceeds the setpoint.
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Citations
15 Claims
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1. A device for detecting, in an electrically propelled automobile having a chassis, an electrical path to the chassis of the automobile from an electric traction system having a floating ground, comprising:
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a traction battery; a traction motor; a positive direct current (DC) line and a negative DC line interconnecting the traction battery and traction motor; a positive sampling circuit electrically connected to the positive DC line for generating a first voltage representative of electric current flow from the battery; a negative sampling circuit electrically connected to the negative DC line for generating a second voltage representative of electric current flow back to the battery; an summing circuit electrically connected to the positive and negative sampling circuits for generating a summed signal representative of the first and second voltages; and a comparator electrically connected to the summing circuit for comparing the summed signal to a first reference signal which is proportional to the traction battery voltage and outputting a fault signal in response thereto when an electrical path exists between the chassis and the traction battery. - View Dependent Claims (2, 3, 4, 5)
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6. A fault detection system for detecting an unwanted electrical path between an electrical traction system of an electric automobile having a chassis and the chassis of the automobile, comprising:
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a signal sampler having a plurality of resistor capacitor (rc) circuits selectively interconnecting the traction system with the chassis for generating first and second voltages which establish a balanced signal in the absence of an unwanted electrical path between the traction system and the chassis, the first and second voltages establishing an unbalanced signal defining a magnitude in the presence of an unwanted electrical path between the traction system and the chassis; and an output circuit electrically connected to the signal sampler for generating a fault signal when the magnitude of the unbalanced signal equals a predetermined magnitude. - View Dependent Claims (7, 8, 9, 10)
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11. A method for detecting an electrical leakage path between an electric traction system of an electric automobile and the chassis of the automobile, comprising the steps of:
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(a) generating a first voltage by storing energy representative of electric current flow through a positive electrical conductor of the traction system; (b) generating a second voltage by storing energy representative of electric current flow through a negative electrical conductor of the traction system; (c) adding the voltages to generate a sum voltage; (d) establishing a setpoint voltage; (e) comparing the sum voltage to the setpoint voltage; and (f) outputting a fault signal when the sum voltage exceeds the setpoint voltage. - View Dependent Claims (12, 13)
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14. A hardware or software system for detecting an electrical leakage path between an electric traction system of an electric automobile and the chassis of the automobile, comprising:
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(a) means for generating a first voltage representative of electric current flow through a positive electrical conductor of the traction system; (b) means for generating a second voltage representative of electric current flow through a negative electrical conductor of the traction system; (c) adding means connected to the generating means for adding the voltages to generate a sum voltage; (d) means for establishing a setpoint voltage; (e) comparing means connected to the adding means for comparing the sum voltage to the setpoint voltage; and (f) output means connected to the comparing means for outputting a fault signal when the sum voltage exceeds the setpoint voltage. - View Dependent Claims (15)
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Specification