Abstract: To cool electronic heat producing elements and components which are normally connected to a heat sink, an evaporator containing a circulating coolant is thermally connected to each of the heat producing components. The evaporator absorbs the heat from the heat producing element. The coolant is boiled or evaporated within the evaporator. The pressure on the gas produced by the evaporation is maintained at a constant pressure. This will result in a uniform temperature of the liquid as it is being evaporated. The heat producing components, therefore, will be maintained at substantially a constant temperature. Several heat producing elements may be connected to a single evaporator. For retrofitting existing units, individual evaporators are made to attach to the heat sink between the heat producing component and the heat sink.

Abstract: Electronic components are mounted upon a chassis which slides vertically inside a tank. The components are normally cooled by circulating transformer oil around them. When inspection, maintenance or repair work is required, the bottom of the chassis is sealed to the side of the tank, an opening in the bottom of the chassis is closed and the chassis elevated by pumping the transformer oil beneath the chassis bottom.

Abstract: A circuit for detecting arcing in a vacuum contactor in a polyphase system, caused by development of an air leak. A current transformer and sensing means, which may be independent of or which may work in conjunction with a conventional ground fault relay, senses the unbalanced leakage current and activates warning and protection circuits so as to prevent damage to the rest of the system. The protection system is activated or switched into a higher sensitivity mode when the vacuum contactor is supposed to be open so as to detect relatively small leakage currents. When the vacuum contactor is supposed to be closed, the system is disabled or is operated in a lower sensitivity mode so as to detect ground faults, but so as not to be tripped by normal surges and transients during operation of the system.