The importance of mechanics in the design of switchgear is emphasized, and attention is drawn to the desirability of applying to switchgear the best that mechanical science has to offer. The functions of switching apparatus are set out in detail and the forms usually taken by the devices for performing these functions, and their relationships to each other, are described. The following are instanced as typical mechanical problems in switchgear design: the strength of complex enclosures against internal pressure; oil-tight joints with insulators; the use of Portland cement with insulators; mechanisms for operating circuit breakers, including internal linkages and external actuating devices; the design of contacts. Essential and arbitrary variations in switchgear design are considered, the former including voltage, amperage, frequency, breaking capacity, and location; and the latter, evolution, economic pressure, safety requirements, and individual preference. The incidence of the causes of variation is indicated and some attempt is made to describe their range of action. A short summary is given of the effects of the wide variety in demand, and the expected course of future progress is indicated. Appendixes are given exemplifying the application of simple mechanical calculations to circuit breaker mechanisms, and the usual loadings on various forms of contacts are tabulated.
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