Method and apparatus to monitor loss of ground isolation of an electric motor drive circuit
AssigneeGM Global Technology Operations LLC
InventorsS.M. Nayeem Hasan, David P. Tasky, Mohammad N. Anwar, Wei D. Wang
Life of this patent
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Abstract
A method for monitoring electric isolation of a high voltage DC bus to detect ground isolation faults includes monitoring voltage differentials between a positive DC electric power bus and a negative DC electric power bus and a chassis ground. Electrical isolation between each of the positive and negative DC electric power buses and the chassis ground is monitored using a ratio of the voltage differentials.
Claims16
Method for monitoring electrical isolation of a DC electrical power circuit relative to a chassis ground, the method comprising:
- monitoring a first electrical potential comprising a voltage differential between a positive DC electric power bus and a negative DC electric power bus;
- monitoring a second electrical potential comprising a voltage differential between the positive DC electric power bus and the chassis ground;
- monitoring a third electrical potential comprising a voltage differential between the negative DC electric power bus and the chassis ground;
- calculating a first voltage ratio comprising a ratiometric comparison of the third electrical potential to the second electrical potential;
- monitoring electrical isolation between the positive DC electric power bus and the chassis ground based upon the first voltage ratio;
- and
- monitoring electrical isolation between the negative DC electric power bus and the chassis ground in relation to the first voltage ratio and the first electrical potential.
Method for monitoring electrical isolation between a DC electrical power circuit and an electric ground, the DC electrical power circuit including an electric energy storage device electrically connected via a positive DC electric power bus and a negative DC electric power bus to an electric power inverter device, the method comprising:
- monitoring a first potential comprising a voltage differential between the positive DC electric power bus and the negative DC electric power bus;
- monitoring a second potential comprising a voltage differential between the positive DC electric power bus and the electric ground;
- monitoring a third potential comprising a voltage differential between the negative DC electric power bus and the electric ground;
- calculating a first voltage ratio comprising a ratio of the third potential and the second potential;
- detecting a fault associated with electrical isolation between the positive DC electric power bus and the electric ground when the first voltage ratio exceeds a first ratio threshold;
- detecting a fault associated with electrical isolation between the negative DC electric power bus and the electric ground when the first voltage ratio is less than a second ratio threshold and the first potential is greater than an isolation threshold voltage;
- and
- detecting a fault associated with electrical isolation between the negative DC electric power bus and the electric ground when the first voltage ratio is less than a third ratio threshold and the first potential is less than the isolation threshold voltage, wherein the third ratio threshold is less than the second ratio threshold.
Dependencies are inferred from the claim text.