Abstract: An isolation fault detection system for detecting isolation faults in a fuel cell system associated with a fuel cell hybrid vehicle. The isolation fault detection system measures a stack voltage potential, a positive fuel cell voltage potential, a negative fuel cell voltage potential, a positive battery voltage potential, and an overall battery voltage potential. The isolation fault detection system then uses these voltage potentials in mesh equations to compare the measured voltage potentials to voltage potentials that would occur during a loss of isolation. In one embodiment, the isolation fault detection system uses these five measured voltage potentials to determine whether an isolation fault has occurred at four separate locations in the fuel cell hybrid vehicle. The system also can detect the location of the isolation fault.

Abstract: A scheme is provided for reducing the degree to which EMI from high voltage components of a fuel cell system or a fuel cell powered vehicle is induced in low voltage components of the system or vehicle. In accordance with one embodiment of the present invention, the electrical components of the system's high voltage region and the electrical components of the system's low voltage region are positioned such that, absent EMI shielding structure between the high and low voltage components, a substantial amount of EMI from the high voltage components would be induced in the low voltage components. EMI shielding structure is configured to define a conductive enclosure about the high voltage region and the low voltage region and a conductive EMI barrier between the high voltage region and the low voltage region.

Abstract: An isolation fault detection system for detecting isolation faults in a fuel cell system associated with a fuel cell hybrid vehicle. The isolation fault detection system measures a stack voltage potential, a positive fuel cell voltage potential, a negative fuel cell voltage potential, a positive battery voltage potential, and an overall battery voltage potential. The isolation fault detection system then uses these voltage potentials in mesh equations to compare the measured voltage potentials to voltage potentials that would occur during a loss of isolation. In one embodiment, the isolation fault detection system uses these five measured voltage potentials to determine whether an isolation fault has occurred at four separate locations in the fuel cell hybrid vehicle. The system also can detect the location of the isolation fault.

Abstract: A scheme is provided for reducing the degree to which EMI from high voltage components of a fuel cell system or a fuel cell powered vehicle is induced in low voltage components of the system or vehicle. In accordance with one embodiment of the present invention, the electrical components of the system's high voltage region and the electrical components of the system's low voltage region are positioned such that, absent EMI shielding structure between the high and low voltage components, a substantial amount of EMI from the high voltage components would be induced in the low voltage components. EMI shielding structure is configured to define a conductive enclosure about the high voltage region and the low voltage region and a conductive EMI barrier between the high voltage region and the low voltage region.

Abstract: An electrical isolation system is provided for a fuel cell stack as well as a method of operating the fuel cell stack. The stack comprises a plurality of fuel cells connected in series and a coolant circuit for cooling said fuel cells in operation using a liquid coolant having a restricted electrical conductivity. The stack is associated with a chassis having a chassis ground and comprising a plurality of coolant passages for said fuel cells. The coolant circuit comprises a plurality of conductive components such as an outer boundary wall of the fuel cell stack, a radiator and/or a pump at least one of which is connected to said chassis ground. A measuring circuit is provided for measuring the resistance between a selected one of the fuel cells and the chassis ground and a monitoring circuit provides a warning signal, or disengages the connection to the output terminals of the stack or shuts down the stack if the resistance reaches a critical value.

Abstract: An electrical isolation system is provided for a fuel cell stack as well as a method of operating the fuel cell stack. The stack comprises a plurality of fuel cells connected in series and a coolant circuit for cooling said fuel cells in operation using a liquid coolant having a restricted electrical conductivity. The stack is associated with a chassis having a chassis ground and comprising a plurality of coolant passages for said fuel cells. The coolant circuit comprises a plurality of conductive components such as an outer boundary wall of the fuel cell stack, a radiator and/or a pump at least one of which is connected to said chassis ground. A measuring circuit is provided for measuring the resistance between a selected one of the fuel cells and the chassis ground and a monitoring circuit provides a warning signal, or disengages the connection to the output terminals of the stack or shuts down the stack if the resistance reaches a critical value.