FIELD: electrical engineering.
SUBSTANCE: invention refers specifically to A C electric systems in which nonrated voltages or currents can emerge under rated operational conditions in power supply system or as result of emergency. It is used for protection of user when voltage or current deviate above preset values. Gear has two threshold elements, actuator used at same time as protective unit, timer with light-emitting diode of optron, measurement unit. Threshold elements send switch-off signal to timer when network voltage is above or beneath specified level via measurement unit. Gear also has temperature sensitive resistor-temperature sensor, current transformer. Actuator is made up of two field-effect transistors and protective diodes connected in series opposition. Sources of field-effect transistors are connected by common wire of control circuit, which includes connected in parallel reservoir capacitor and stabilizer diode connected through damping resistor to rectifier of network voltage based on diode. Gates of field-effect transistors are connected through current-limiting resistor and nonpolar stabilizer diode in parallel to user and through photodiode of optron to common wire of control circuit. Measurement unit sends signal to cut off user from network with rise of load current measured by current transformer or with increase of temperature of field-effect transistors measured by temperature-sensitive resistor-temperature sensor.
EFFECT: increased speed of operation of protection, limited voltage amplitude across user, current and overheating protection of power transistors, control over time of delay of switching on, reduced radio jamming.
1 dwg
