decided how many 20x20 m (65.6 ft.) power panels are to feed each power converter. Figure 5-1 shows the basic diode panel. Fig. 5-1. Diode Panel (Heat Pipe Side) X power converter could be located on this panel; however, the radiator for this converter would displace approximately one fourth of the diodes. The converter power rating would be approximately 2.6 MW. The combined efficiency of the d.c. to a.c. converter and its associated transformer would be approximately 0.92 at this power rating; the specific mass would be about 0.35 kg/kW (0.77 Ibm/kW). By using four diode panels per power converter panel, as shown in Figure 5-2, a larger (14 MW) converter is possible. The waste heat rejection from a 14 MW converter/ transformer is just appropriate to a 20x20 m (65.6 ft) panel at a heat rejection temperature of 405 K (269°F). Also, four diode panels may be grouped around such a panel quite conveniently. At a 14 MW rating the power converter assembly has an efficiency of 0.96 and a specific mass of 0.29 kg/kW (0.63 Ibm/kW). Since the currents are so high good busbar design is required to achieve lightweights. Flat, high area busbars reject I-R losses well if given a high emissivity coating. Insulation is required beneath the busbars to shield them from the high temperature of the cavity interior. The insulation used is "Multi-Foil" (see Section 4-6). A busbar width of one meter (3.28 ft.) was selected as a good compromise between obtaining sufficient radiator area and the concommittant enlargement of the cavity absorber, insulation mass increase, etc. On the diode panel the current handled by the busbar is a maximum at the connection to the power converter panel and a minimum at the other edge of the diode panel (the left side of Figure 5-1). This current distribution makes tapering the thickness of the busbar a practical method of mass reduction. Aluminum proved to yield a lighter conductor than copper when each was optimized to yield minimum mass for the busbar itself plus the SPS penalty from the I^R loss in the busbar (this penalty was taken as 8.31 kg/kW of Pr dissipation). The optimum aluminum busbar temperature is 450 K (350°); the optimum copper temperature would be 700 K (800°F). The aluminum busbar should be 1.17 cm (0.46 in.) thick at the point of connection to the diode panel; it may be only 0.56 mm (0.022 in.) thick at the other end. The busbars are 2 m (6.56 ft.) wide and 1.17 cm (0.46 in.) thick on the power converter panel. A circuit for the busbars of four diode panels and a power converter panel is given in Figure 5-3.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==