Abstract: An exemplary power plant assembly includes a plurality of cell stack assemblies each having a plurality of fuel cells and a manifold. A fuse includes an indicator that provides an output when the fuse interrupts an electrically conductive connection between the manifold of a first one of the cell stack assemblies and a second one of the cell stack assemblies. The electrically conductive connection includes at least a portion of the voltage of the second one of the cell stack assemblies.

Abstract: A power system (110; 210; 310) combines a power source (14) having a DC output (20A, 20B) with an AC supply from the AC grid (12) to provide AC to customer's loads (16) and DC to various DC auxiliary loads (134, 134A). The DC output of the DC power source (14) is connected in steady-state to the DC input (120A, 120B, 60) of a converter/bi-directional inverter (122; 222) for conversion therein to AC for connection (124, 124A, 32) to the customer's loads (16) and (124, 124B) to any AC auxiliary loads (134, 234). During start-up of the DC power source (14), an open isolation switch (70) disconnects that DC power source (14) from the bi-directional inverter (122; 222). A start-up power supply (50, 60; 250, 60; 90, 180, 60) selectively connects (56; 94) between the AC power grid (12) and the bi-directional inverter (122; 222) and/or DC controllers (134A) to provide a supply of rectified DC power at the inverter DC input and to certain DC auxiliary loads (134, 234).

Abstract: An exemplary power plant assembly includes a plurality of cell stack assemblies each having a plurality of fuel cells and a manifold. A fuse includes an indicator that provides an output when the fuse interrupts an electrically conductive connection between the manifold of a first one of the cell stack assemblies and a second one of the cell stack assemblies. The electrically conductive connection includes at least a portion of the voltage of the second one of the cell stack assemblies.

Abstract: A power system (110; 210; 310) combines a power source (14) having a DC output (20A, 20B) with an AC supply from the AC grid (12) to provide AC to customer's loads (16) and DC to various DC auxiliary loads (134, 134A). The DC output of the DC power source (14) is connected in steady-state to the DC input (120A, 120B, 60) of a converter/bi-directional inverter (122; 222) for conversion therein to AC for connection (124, 124A, 32) to the customer's loads (16) and (124, 124B) to any AC auxiliary loads (134, 234). During start-up of the DC power source (14), an open isolation switch (70) disconnects that DC power source (14) from the bi-directional inverter (122; 222). A start-up power supply (50, 60; 250, 60; 90, 180, 60) selectively connects (56; 94) between the AC power grid (12) and the bi-directional inverter (122; 222) and/or DC controllers (134A) to provide a supply of rectified DC power at the inverter DC input and to certain DC auxiliary loads (134, 234).

Abstract: An auxiliary load (148) for a fuel cell stack (102) is alternatively connected and disconnected from the fuel cell external circuit (177, 178) by a switch (200) in response to a switch control (201), repetitively, during startup and shutdown. The switch may be an insulated gate bipolar transistor (208) which is turned on and off by hunting between an upper limit voltage (207) and a lower limit voltage (208), which may be performed by compare circuits (205, 206), by the controller (202), or by commercially available voltage responsive hysteresis switches. Schedules of duty cycle as a function of cell stack voltage for startup (212) and shutdown (213) control a pulse width modulator (215) which operates the switch. Controls (229, 231) may limit the modulation so that the auxiliary load does not overheat, in response to temperature (221) of the load or a voltage/power model (235). The auxiliary load may comprise a heater in a water accumulator (247), an air intake (257) or an enthalpy recovery device (262).