DEVICE FOR LOAD PROTECTION AGAINST ABNORMAL CURRENT AND VOLTAGE IN AC MAINS INCORPORATING AMPLITUDE LIMITER Russian patent published in 2004 - IPC

FIELD: electrical engineering; load disconnection from ac supply mains in case of current and voltage deviation from specified values. SUBSTANCE: device that functions to disconnect load from ac supply mains on occurrence of abnormal currents and voltages with power system operating normally incorporates protective gear responding to overcurrent and overheating of power thyristors and incorporating provision for regulating on-operation time delay for limiting voltage amplitude across supply mains has two threshold elements and final element that includes two bipolar transistors and protective diodes connected in series opposition and functions as protective device; measuring unit; timer; optocoupler light-emitting diode; temperature sensing thermistor; and current transformer; emitters of bipolar transistors are connected to common wire of control circuit that has parallel-connected storage capacitor and voltage regulator diode connected through dropping resistor to supply voltage rectifier built around diode; bases of bipolar transistors are connected through current-limiting resistor and nonpolar voltage regulator diode in parallel with load and through optocoupler photodiode, to common wire of control circuit. EFFECT: enhanced speed of protective gear response; reduced noise immunity. 1 cl, 1 dwg