Cut-off arrangement for and method of protecting a ballast-starter

Abstract

A cycling cut-off arrangement and method of protecting from burn-out a ballast-starter of a luminaire having a power source normally connected to the ballast-starter, and a high pressure sodium lamp across which the ballast-starter supplies voltage of predetermined magnitude to operate the lamp, in the event of a cycling malfunction wherein the lamp is extinguished and the ballast-starter applies a voltage of greater magnitude than the predetermined magnitude across the extinguished lamp. The voltage across the lamp is detected, and a current signal is generated when the voltage magnitude across the lamp reaches a threshold magnitude which is greater than said predetermined magnitude. In response to the generation of the current signal, the power source is disabled from the ballast-starter to protect the latter from damage. A latching-type switch is employed to maintain the disabled condition of the ballast-starter, and a manual reset push button serves to reset the ballast-starter back to its normally-connected condition with the power source. A timer switch generates a timer signal lasting for a predetermined time period which begins upon power resumption after a power malfunction of duration less than said predetermined time period. The timer signal makes the latching-type switch inoperative during the predetermined time period to thereby prevent disablement of the ballast-starter in the event of a power malfunction.