Push-Button Hybrid Switch

A low-current (5-A) push-button hybrid switch is described that combines mechanical contacts and electronics to extend contact life and improve switching performance. The switch is a two-wire type and makes use of three contacts that are opened and closed in sequence. This structure provides virtually arcless switching while minimizing the number of electronic components required. The electronics, consisting of a thyristor and other control circuitry, makes and breaks the circuit, providing zero-voltage turn on and zero-current turn off. It is powered directly by the voltage across the switch and requires no external Power supply. The contacts isolate the electronics from the line, initiate the control electronics, and provide a steady-state conduction path for the current (bypassing the electronics). The arc transfer process is examined for the short arc times observed, as is the contact erosion versus the number of switch operations for both normal and "short delay" operations, and pip and crater formation on the contacts. The inverse relationship between the mechanical and electronic complexity of hybrid switches is examined. Multiple contact arrangements for obtaining the desired functions with a minimal amount of electronics are discussed.