Method and apparatus for monitoring fuel cells
AssigneeGM Global Technology Operations LLC
InventorsRichard M. Breese, Thomas P. O'Meara, Stanley K. Fujii, Bernd Peter Elgas, Stephen Raiser
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Abstract
Methods and apparatus are provided for monitoring a coolant conductivity of a fuel cell supplying power via positive and negative buses. The method includes measuring a first voltage of the positive bus, measuring a second voltage of the negative bus, applying a resistance between the positive bus and a reference potential, measuring a third voltage of the positive bus after a period of applying the resistance, and determining an isolation resistance based on the measured voltages. The isolation resistance is a function of the coolant conductivity.
Claims20
A method for monitoring a fuel cell having a coolant conductivity, the fuel cell supplying power via positive and negative buses, the method comprising the steps of:
- measuring a first voltage from the positive bus to a reference potential;
- measuring a second voltage from the negative bus to the reference potential;
- applying a pre-determined resistance between the positive bus and the reference potential;
- during a single voltage cycle, measuring a third voltage from the positive bus to the reference potential after a first pre-determined time period after said applying step;
- and
- determining an isolation resistance based on the first voltage, the second voltage, and the third voltage that was measured during the single voltage cycle, wherein the isolation resistance is a function of the coolant conductivity.
An apparatus for measuring an isolation resistance in a fuel cell system, the apparatus comprising:
- a first bus configured to couple with a fuel cell anode;
- a second bus configured to couple with a fuel cell cathode;
- a resistor having a first terminal coupled to said first bus and having a second terminal;
- a switch coupled to said second terminal of said resistor, said switch configured to selectively couple said second terminal of said resistor to a reference potential;
- and
- a controller having a control output controlling said switch and having a first and a second input coupled to said first and second buses, said controller configured to:
- direct said switch to close;
- measure a voltage across said resistor after said switch is closed for a first pre-determined time period during a single voltage cycle;
- and
- determine the isolation resistance based on said voltage measured during said single voltage cycle.
A method for monitoring an isolation resistance of a high voltage (HV) bus powered by a fuel cell, the HV bus having positive and negative nodes, the method comprising the steps of:
- measuring a first voltage from the positive node of the HV bus to a reference potential;
- measuring a second voltage from the negative node of the HV bus to the reference potential;
- coupling a pre-determined resistance across the positive node of the HV bus and the reference potential;
- measuring a third voltage between the positive node of the HV bus and the reference potential after a first predetermined time period during a single voltage cycle from said coupling step;
- determining an isolation resistance based on the first voltage, the second voltage, and the third voltage measured during the single voltage cycle;
- and
- transmitting a signal if the isolation resistance if less than a pre-determined percentage of a minimum resistance, the signal indicating a low isolation resistance of the HV bus.
Dependencies are inferred from the claim text.