Abstract: A fuel cell system is provided that includes a fuel cell stack with a plurality of fuel cells and a power converter in electrical communication with the fuel cell stack. The power converter is configured to selectively regulate a power of the fuel cell stack and short circuit the fuel cell stack, as desired. A method for starting the fuel cell stack is also described including the steps of causing a short circuit of the fuel cell stack by placing the power converter in a short circuit mode; introducing a hydrogen to the anodes of the fuel cell stack to displace a quantity of air on the anodes; and placing the power converter in a power regulation mode. A degradation of the fuel cell stack during start-up is thereby militated against.

Abstract: A method and apparatus for a high frequency resistance measurement instrument with a reasonable dynamic range, which militates against saturation in the presence of one or more large undesirable signals, the high frequency measurement instrument capable of employing multiple alternating currents of differing frequencies to maintain measurement capability despite signal chain saturation in the presence of a large undesirable signal.

Abstract: At least one positive temperature coefficient element is used to efficiently control fuel cell voltage at startup and shutdown making the fuel cell more efficient and protecting the electro catalyst layer.

Abstract: A method and apparatus for a high frequency resistance measurement instrument with a reasonable dynamic range, which militates against saturation in the presence of one or more large undesirable signals, the high frequency measurement instrument capable of employing multiple alternating currents of differing frequencies to maintain measurement capability despite signal chain saturation in the presence of a large undesirable signal.

Abstract: A control system for delivering a constant fuser temperature despite variations in the line voltage is effected by a control circuit which employs closed loop feedback control to control the rms voltage across the load. This is accomplished by a circuit and method which functionally provides a continuous solution to the equation which describes the relationship between the temperature of the fuser and the temperature of a desired control setpoint. Briefly, the solution of this equation is obtained by monitoring, i.e. sampling, the temperature of the fuser, subtracting the desired control temperature, and then integrating the difference over time. The resultant time integral is used to control the operating point of a pulse width modulated power controller. The integrator has a time constant sufficiently long and the power controller operates at a frequency sufficiently high so as to render lighting flicker imperceptible.

Abstract: A control system for delivering a constant fuser temperature despite variations in the line voltage. In general, this is effected by a control circuit which employs closed loop feedback control to control the rms voltage across the load. This is accomplished by a circuit and method which functionally provides a continuous solution to the equation which describes the relationship between the temperature of the fuser and the temperature of a desired control setpoint. Briefly, the solution of this equation is obtained by monitoring, i.e. sampling, the temperature of the fuser, subtracting the desired control temperature, and then integrating the difference over time. The resultant time integral is used to control the operating point of a pulse width modulated power controller. The integrator has a time constant sufficiently long and the power controller operates at a frequency sufficiently high so as to render lighting flicker imperceptible.