Aircraft switchgear

An aircraft electrical power system involves the same control, distribution and protection problems as any land-based electrical supply undertaking, and while the design of equipment is eased by the use of lower voltages and powers, it is complicated by the necessity of operating reliably for long periods with little maintenance under widely varying atmospheric conditions, and extremes of vibration and acceleration. The paper emphasizes the importance of close co-operation between the aircraft designer and the electrical equipment manufacturer to avoid incompatibility of requirements and to ensure that all normal and abnormal operating conditions are fully appreciated. It indicates that, as generated powers increase, specialized design for most components will be necessary. The design of current-carrying elements and methods of assessing the rupturing capacity of switchgear are considered, together with the effects of voltage, frequency and altitude on these parameters. The types, functions and general methods of construction of control relays and switching equipment are discussed in relation to weight-saving and reliability. The paper concludes with a brief analysis of the problems involved in the design of equipment to operate at very high temperatures and altitudes, and demonstrates the necessity for further development work on insulating materials and constructional methods.