A homopolar generator for high current low voltage D.C. supply

摘要

A general theory of Homopolar Generator Design is given, including estimation of brush friction loss and conditions for stable operation when conducting large currents. A tabulated survey of the principal ohmic losses and power absorbed by brush friotion is given for a 10kW generator. Three operating conditions are considered, ranging from 4,000 amps. at 2.5 volts to 16,000 amps. at 0.625 volts. Brush stability is examined and overall merits of sodium-potassium alloy and mercury as the brush liquid are con¬sidered. It is shown that there are designs of 90~95％ efficiency using mercury or alloy brushes, but mercury is to be preferred as it ensures greater brush stability under momentary overload and involves fewer development problems. A design of approximately 90％ efficiency with mercury brushes is detailed. It has a rotor of radius 16 cms. length in gap 6 cms., and is run at 935 r.p.m. with gap flux 10,700 gauss to give 10,000 saps. at 1.0 volt and at 780 r.p.m., 8,000 gauss, to give 16,000 amps. at 0.625 volt.