Internal Power Supply

However, when the same battery was discharged at -10°C and 1.5 C, its voltage dropped to below 43 V instantly, and therefore it was not adequate enough to provide power for a load that required a minimum input voltage 

Since a battery typically shows poor performance at subzero temperatures, external heating may be needed to keep its temperature above 0°C. 

Components such as the control boards, solenoid valve, blower, fans, pump, switches, and sensors also need power from the battery during the startup process. These components may need 48,24,12, or 5 V, and DC-EXZ converters are needed to convert the voltage from the internal power supply module to those values. When the fuel cell system is in the idling state, the mother board and various sensors are also powered by the internal power supply module. 

Once the stack starts to provide power, it shares the load with the battery in the beginning, and all of the load will be quickly powered by the stack. The power needs of the components mentioned above can then come entirely from the system s main DC-DC converter. The battery could also be charged by the system s main DC-DC converter. 

If the internal battery is charged by the stack while the stack is in operation, the stack must be able to meet the power needs of both the load and the battery. If the battery has a large capacity and is quite empty, its power needs can be significant. It is better to limit the charging current to the battery to prevent it from withdrawing too much power. The combined power need from the load and the battery should not exceed the stack s designed capacity. 

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Checks on the internal electronics, such as verifying that the voltage levels of internal power supplies are within specifications. 

An internal power supply module provides the power needed by certain components within a fuel cell system. The components include sensors, control boards, pumps, fans, blowers, compressors, solenoid valves, contactors, switches, and so on. The IPM also provides the power to start the fuel cell system and helps carry some load when the fuel cell stack is inadequate to handle a sudden load jump. There are many types of sensors in a fuel cell system, such as the H2 concentration sensors, the H2 pressure sensors, the fluid flow rate sensors, the coolant-level sensors, the temperature sensors, the current sensors, the voltage sensors, the door-open sensors, the vibration sensors, and the flooding sensors. These sensors monitor the corresponding parameters to indicate the situation of the entire fuel cell system. The control boards may include a main board for controlling the system and several sub-boards for controlling various modules discussed in this chapter. Pumps, fans, blowers, compressors, solenoid valves, contactors, and switches all require power to perform the corresponding functions. 

Electronic and PE logic solvers frequently include internal power supplies that convert electrical power source(s) to lower-level voltages for internal use. Power supply redundancy should be considered to meet the reliability requirements of the application. 

The DAS and the PMS use independent and separate power sources and internal power supplies. 

Of course for the realization of a control system (compare to Fig. 4.24) we would need parts such as housing, a plug connector, a power supply (external periphery like the battery etc.) as well as internal components such as a printed circuit board (PCB), internal power supply and voltage distribution (internal periphery). Now we need to decide how we consider the control unit. 

The watchdog cards of each unit determine an external watchdog based on intrinsic safety relays (using gravity). The relay contacts on the watchdog card are placed in series with those of the watchdog of the dual unit, in order to operate the safety relay that disconnects all internal power supply and especially towards the external safety interfaces (relay signaling). 

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