INTEGRATED PROTECTIVE GEAR FOR THREE-PHASE LOADS Russian patent published in 1998 - IPC

FIELD: electrical engineering; protection of symmetrical and asymmetrical loads including induction motors. SUBSTANCE: protective gear has final element and sensor made in the form of current transformer with resistive load, as well as reverse-sequence sensor, five voltage dividers, comparator, and trigger which functions under emergency conditions to act upon actuating mechanism and final element that provides for hyperbolic overload characteristic (that is, overload time as function of its ratio). Comparator and trigger may be built around digital CMOS logic elements. Time-setting unit provided for regulating heavy starting conditions of devices with continuous initial overload characteristic has master oscillator, pulse counter, and control circuit that stops or continues pulse counting depending on state of load and actuates final element. EFFECT: enlarged functional capabilities and improved reliability of protective gear. 2 cl, 1 dwg