High-potential testing equipment for quantity production

Manufacturers of electrical apparatus and appliances are aware of the value of high-potential insulation tests and have endeavored constantly to improve testing facilities and methods. Practical circumstances very early gave rise to the practice of applying a short-time test voltage substantially above the normal excitation of the apparatus or appliance. Because of the availability and simplicity of amplitude control, alternating voltage of ordinary power frequency has been used and the test voltage levels have been developed through operational experience. Occasionally circumstances have made the use of power frequency impractical; hence higher frequencies and direct voltage have been resorted to. Also, surge voltage tests have been used increasingly in an effort to simulate transient voltages which occur in field circuits.