SU1566312A1 - Device for monitoring insulation resistance of electric circuits - Google Patents

Abstract

The invention relates to instrumentation technology and can be used in automatic control systems for the insulation resistance of electrical circuits. The purpose of the invention is to increase the speed and noise immunity. The preliminary charge of the capacitance of the test object is carried out up to a voltage equal to the voltage across it at the nominal value of the insulation resistance of the test object. The charge time to the specified voltage is minimized by increasing the charging current through the current limiter 4, the diode 8 and the first switch 9, and also by reducing the capacity of the charging circuit to a value equal to the capacity of the test object. Upon completion of the transient process, when the first switch 9 is opened, the transient process of recharging the capacity of the test object from the initial voltage to the voltage determined by the actual value of its insulation resistance begins. According to the transient process time, the insulation resistance is estimated. If there is interference from the voltage of the industrial network, having the form of a harmonic voltage on the reference resistor 2, it is suppressed in the subsequent stage of the proposed device - on the amplifier 17, which is made according to the integrating amplifier circuit.

Description

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FIG. 2

Claims (2)

Claim 1. Device for automatic 5 15663 through switch 9, the third through resistors 2 and 11. The total charge current is determined by the current limiter 4 and provides a rapid increase in voltage on the capacitance of the test object, which after a certain period of time leads to an increase in potential at the cathode of diode 8, followed by a decrease current through the diode 8, locking the diode 8 and the transition of the amplifier 12 to the linear mode of operation. It is accepted that the resistances of resistors 2 and 11 are the same. The resistances of resistors 14 and 15 are also identical. In this case, diode 8 is under constant reverse voltage equal to the voltage of bias source 6, and the voltage at the output of amplifier 12 is equal to the voltage at the cathode of the diode minus the voltage of source 6. Upon completion of the charge of the capacitance of the test object at the cathode of the diode 8, a potential equal to the potential of the negative bus of the source 5 of the reference voltage 25 is established, and the interference voltage will be zero, since the resistance of the switch 9 and the output resistance of the source of reference voltage 5 are small. thirty The opening of the switches 9 and 19 is carried out at time t, such that T _s / 2 <t <T _C , where T _s is the period of voltage fluctuations of the network. This delay is realized by the trigger 27 in order to guarantee the charge of the capacitance ³³ of the control object to the voltage of the source 5. When the trigger 27 is in the single state, control commands are issued to open the switches 9 and 19. From this moment on, the cathode of the diode 8 starts the exposition of monitoring the insulation resistance of electrical circuits containing a current limiter, two terminals for connecting the monitoring object, a reference resistor, a comparison element, a test voltage source, the first output of which is connected to the first output of a resistor, characterized in that, in order to improve performance and noise immunity, a reference voltage source, a bias voltage source, six resistors, a diode, two amplifiers, a capacitor, two switches, an inverter, a D-trigger and a control unit are introduced into it the first terminal of the test voltage source is connected to the first input of the comparison element, the plus bus of the reference voltage source, the negative bus of the bias voltage source and the non-inverting input of the second amplifier, and the second terminal is connected with a common bus and a first terminal for connecting the control object, the first output of the control unit is connected to the control input of the first switch, the second terminal for connecting the control object is connected to the first terminal of the current limiter and the first terminal of the first resistor, the second terminal of which is connected to the second terminal of the current limiter, the cathode of the diode, the first terminal of the first switch and the first terminal of the second resistor, the second terminal of which is connected to the second voltage change in one direction or the other from the original toyannoy time determined by the capacity control of the object and the resistance of resistors 2 and 11 and the noise voltage appear, and the integrator formed on the second amplifier 17, starts to integrate the varying signal and the interference signal. At the same time, one is set at the D-input of the shift register 32, and at its output with the arrival of each clock pulse to the scrap of the reference resistor and a non-inverting input of the first amplifier, output 45 of which is connected to the first output of the third resistor, the diode anode and the first output of the fourth resistor, the second output of which connected to the inverting input of the first amplifier 50 and the first output of the fifth resistor, the second output of which is connected to the plus bus of the bias voltage source and the first output of the sixth resistor, the second output to orogo connected kicking unit promotions. With the appearance of a unit at the output of the register 32, which is connected to the output of the switch 33, the trigger 30 is set to the initial state, and to you with the second output of the third resistor, the inverting input of the second amplifier, the first output of the capacitor and the first output of the second switch, the control input which is connected to the second output of the control unit, and the second output is connected to the second output of the capacitor, the output of the second amplifier and the second input of the comparison element, whose output is connected to the input of the inverter, the output of which union of a D-input of D-flip-flop, the clock input of which is connected to a third output of the control unit, and a direct output D-flip-flop is connected to the control bus dispensing results. 2. The device according to claim 1, wherein the control unit comprises a converter, a trigger (5 gig, a synchronizer, an inverter, a delay trigger, two power amplifiers, a shift register and a switch, moreover, the output of the converter is connected to the first the synchronizer input, the second input of which is connected to the trigger output and the D- and P-inputs of the delay trigger, the C-input of which is connected to the synchronizer output and the inverter input, the output of which is connected to the C-input of the shift register, whose D- and R-inputs are connected with delay trigger output and usb inputs divisors power, and outputs - to the corresponding inputs of the switch, the output of which is connected to the R-input of the flip-flop.