Startup power systems

Startup Power Systems Fuel cells normally need some external power input to assist startup. An auxiliary high-power battery to run pumps and heaters during startup or to provide power to overcome voltage transients and reversals in the fuel cell stack is often used. 

The achievements of a small Canadian startup company, Ballard Power Systems, in Vancouver, are the main reason for my view that polymeric-membrane cells have the automotive market at their feet. The stages of the company s achievements. 

Figure 5.14 illustrates the situation at the begirming of startup. The system was in an idling state, but the H2 supply was turned on before the grid power was turned off. In such a standby mode, the parasitic power required by the system was supplied by the stack through the system s main DC-DC... 

Throughout this textbook, the PEFC has been emphasized because it is a likely candidate for power replacement for portable, auxiliary, stationary, and automotive power systems. As shown in Figure 6.1, the PEFC class of fuel cells includes the hydrogen, direct methanol, direct alcohol, and other fuel cell systems utilizing a solid polymer electrolyte. While the higher temperature molten carbonate and solid oxide fuel cell systems are well-suited for steady power systems, only the low-temperature PEFC offers the rapid startup and lower operating temperatures (20-90°C) required for transient operation of portable, reserve, and automotive power applications. 

The Heat Rejection Segment provides the heat sink necessary for (deration of the Brayton unit cycle. Full deployment of the radiator panels is required prior to reactor startup and the raising of the power system s temperature. Spacecraft operational planning assumes that trace heaters and a minimum ( survival flow will be utilized to prevent HRS fluids from freezing from launch until operation of the power system. 

The Model 412 PWR uses several control mechanisms. The first is the control cluster, consisting of a set of 25 hafnium metal rods coimected by a spider and inserted in the vacant spaces of 53 of the fuel assembhes (see Fig. 6). The clusters can be moved up and down, or released to shut down the reactor quickly. The rods are also used to (/) provide positive reactivity for the startup of the reactor from cold conditions, (2) make adjustments in power that fit the load demand on the system, (J) help shape the core power distribution to assure favorable fuel consumption and avoid hot spots on fuel cladding, and (4) compensate for the production and consumption of the strongly neutron-absorbing fission product xenon-135. Other PWRs use an alloy of cadmium, indium, and silver, all strong neutron absorbers, as control material. 

Accumulators can be used to help stabilize the lube system against pressure transients such as that from the turbine power operator during a large correction. For a sizing rule of thumb, the system pressure should not vary by more than 10%, while the turbine servo travels full stroke in a one second interval. The role of accumulators for pump switching was covered earlier in the section on Startup Control. 

Automatic and manual initiation demands In addition to test demands, equipment may be activated or deactivated by intended or spurious signals. These signals include losses of offsite power and normal shutdowns or startups. Different components react to different signals or sets of signals, depending on their functions for each system. The... 

Any problems in the setup, startup, and operation of the CBMS also were recorded in the course of the field tests. These observations are important to improving the system before it goes into production. The field tests revealed three problems. The protective screens over electronics cooling air inlets and outlets on the CBMS II housing were damaged by operator activities in the vehicles and required reinforcement. The ground probe head, which protrudes outside the vehicle hull, required more power to maintain the correct temperature under colder or wetter weather conditions. Finally the automated mass and frequency calibration procedure was not reliable in the field and required modification. These problems have been corrected and are being incorporated in the LRIP units. 

Access to the system Is gained through an automatic startup command procedure ("Turn on Computer" in Figure 2) that sets the terminal parameters, sets certain operating system flags, and loads the correct date and time from the battery powered calendar/clock. 

A signal to the reactor protection system at a selected value (normally 10% reactor power) to disable the high startup rate reactor trip... 

In general, most converters are tested on the bench with the electronic load set to constant current (CC mode). True, that s not benign, nor as malignant as it gets. But the implied expectation is that converters should at least work in CC mode. They should, in particular, have no startup issues with this type of load profile. But even that may not be the end of the story Some loads can also vary with time. For example, an incandescent bulb has a resistive profile, but its cold resistance is much lower than its hot resistance. That s why most bulbs fail towards the end of their natural lifetime just when you throw the wall switch to its ON position. And if the converter is powering a system board characterized by sudden variations in its instantaneous supply current demand, that can cause severe problems to the converter, too. The best known example of this is an AC-DC power supply inside a computer. The 12V rail goes to the hard disk, which can suddenly demand very high currents as it spins up, and then lapse back equally suddenly into a lower current mode. 

So where does soft-start really help Mainly in bringing up the output voltage rail smoothly, maybe to avoid jerking the system connected at the output of our power supply. Yes, perhaps within a certain range of output C and L, it can also help control the stresses on the switch at power-up. But that support is hardly unconditional. Maybe it helps somewhat in lowering the overshoot of the rail at startup. But as mentioned in Question 2, it can itself be a reason for the overshoot too. Therefore, in all the AC-DC Flybacks we... 

As long as the equipment is operating, power and treatment chemicals will be consumed. Generally this cost can be calculated on a daily or volume basis. Difficulties can occur when operation is halted on an unplanned occurrence, such as an accidental power disruption or other cause for system stoppage. Restarting and return of the system to a semiequilibrium status can sometimes be as costly as the initial startup. Contingencies should be included for periodic happenings. 

Polymer electrolyte fuel cells (PEFC) deliver high power density, which offers low weight, cost, and volume. The immobilized electrolyte membrane simplifies sealing in the production process, reduces corrosion, and provides for longer cell and stack life. PEFCs operate at low temperature, allowing for faster startups and immediate response to changes in the demand for power. The PEFC system is seen as the system of choice for vehicular power applications, but is also being developed for smaller scale stationary power. For more detailed technical information, there are excellent overviews of the PEFC (1,2). 

System test—turn off all modules and power-up to perform startup diagnostics. Perform static leak test of the pump and compression test of the autosampler as suggested by the manufacturer. 

Assure proper power-up or startup of the system components. 

---