I.2.2 Power Distribution (References: 77/15,77/16,78/1,78/5,78/22,78/55.) I.2.2.1 General This category implies the delivery of the electrical DC power from the solar cell modules to the microwave generators, including connections, rotary joints, conductor materials, and any regulation and control equipment. Most SPS-concepts use high-voltage DC-power with voltage levels between 20 and 44 kV. The GSSPS-concept distributes the power by microwave in waveguides. The cascaded-dielectric-de- vice concept by Drummond uses 60 Hz or DC alternatively. The high voltage levels in the DC-distribution concepts were selected considering the requirements of the microwave generators and the conductor mass. In the GSSPS-concept a 2 kV DC-subsystem was selected because of the voltage limits for the microwave transistors, which are used for RF-generation. The weight of the power distribution system should be in a range of 8 % - 14 % of total SPS mass. I.2.2.3 Conductors In this sub-category the literature shows very different approaches. It is not quite clear if the conductors shall be actively cooled as superconductors. Only the choice of aluminum as material was corresponding throughout the literature because of its low mass to conductivity ratio and good radiation cooling properties. The geometric shape of the conductors depends on the amount of waste heat to be rejected. The GSSPS concept uses cryogenically cooled aluminum conductors for the 2 kV DC-distribution and overmoded cylindrical waveguides for the microwave distribution. The waveguide material is a graphite/aluminum composite. 1.2.2.4 Interfaces There are little data available in literature concerning this sub-category. Some items are: - B£tary_joints are used as slip-rings for the high voltage transmission to the antenna. Waveguide rotary joints are used in the GSSPS together with tapered flares. - Switching_gear will perhaps be designed as superconducting devices, but these are currently limited to a few hundred amperes and a few thousand volts. Other approaches are liquid metal plasma valves or solid state gates. - DC-DC converters or regulators are identified as a severe problem for the high voltage distribution.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==