SU951534A1 - Voltage indicator - Google Patents

Description

 VOLTAGE SIGNALING DEVICE

one

The invention relates to voltage monitoring devices and can be used in automation systems.

A voltage presence signaling device is known that contains a polarized relay, the first and second windings of which are connected between the output circuits of the power source parallel to the load. A diode and a large resistance resistor, shunted by a capacitor, are connected in series to the first winding circuit. A thyristor and a second diode are connected in series in the circuit of the second winding. The control electrode of the thyristor is connected to the negative power supply circuit of the terminal. A large resistance resistor is connected between the cathode and the control electrode of the thyristor Cl.

However, the normal operation of this circuit depends on the load through which the discharge of the second capacitor takes place, as a result of which the thyristor is activated, which triggers the operation of the polarized relay. Consequently, disturbances in the power buses as a result of a load operation or as a result of external magnetic and electromagnetic fields can cause a false alarm device. In addition, this voltage presence detector has a low reliability and limited scope due to the dependence of circuit performance on the load parameters.

A device for monitoring voltages is known, comprising a three-phase rectifier, three resistors, two Zener diodes, a diode, a capacitor, two transistors and a thyristor. The positive rectifier bus is connected via a resistor to the base of the first transistor and the anode of the diode, the cathode of which is connected to the emitter of this transistor and one of the terminals of the t2J capacitor.

However, as a result of the interference in the power bus, there may be a voltage between the base and the emitter of the specified transistor, which opens it. As a result, the thyristor opens and the actuation of the actuator occurs. In addition, this circuit also requires a separate power source for the actuator (not shown in the diagram),. which greatly narrows the field of application of a voltage monitor.

The closest in the technical essence to the invention is a voltage detector containing a polarized relay with two windings. One winding is connected between the supply circuits, and the power supply is parallel to the load. A controlled switching diode (thyristor) is connected in series with this winding. The thyristor control electrode is connected to the supply circuit with a thyristor-locking polarity. The coherent second winding and thyristor are connected parallel to the capacitor. A high-resistance resistor is connected between the common point for the capacitor and the first winding and the control electrode of the thyristor. The magnitude of this resistance is limited only by the need to provide a control current sufficient to unlock the thyristor 33.

The disadvantages of the known signaling device are the poor noise immunity of the circuit if the power source and the voltage signaling device are with a considerable distance from each other. Interference to the common power supply wire as a result of magnetic and electromagnetic fields may cause interference, as a result of which the thyristor opens, which causes a false positive of the polarized relay. The thyristor opens as a result of the fact that the potential of the control electrode, due to the effect of interference, becomes positive relative to the cathode. Especially for an hour this is observed in thyristors with a small discharging current. In addition, this scheme does not allow the use of a detector to control the loss of one or more phases when the load is supplied with three-phase current.

The purpose of the invention is to improve the noise immunity of the circuit.

The goal is achieved in that a voltage detector, containing a power source and a succession of 1o, is connected to a winding polarized relay, a capacitor and a diode, the cathode of which is connected to the negative terminal of the power source, and the resistor is additionally equipped with an optocoupler, a second diode and a capacitor, positive the output of the power source through the closing contact of a polarized relay, shunted by a button, is connected in series with one output of a resistor - and a positive capacitor plate, p parallel to which, the first winding of the polarized relay with a sequentially connected in the forward direction thyristor of the optocoupler is turned on, and the second winding of the polarized relay is connected between the negative capacitor plate and the anode of the diode, the cathode of which is connected to the second terminal of the optocoupler whose cathode is connected to the anode the second diode, the cathode of the latter is connected to the negative capacitor plate, in addition, the LED of the optocoupler is shunted by a second capacitor.

The drawing shows a voltage detector circuit.

Claims (3)

The voltage detector contains a power source 1, the positive output of which is connected to the Start button 2 and the closing contact 3, the second inputs of which are connected to the positive capacitor plate, the first output of the resistor 5 and the winding of the polarized relay 6. The negative capacitor plate k is connected to the second winding polarized relay 7, the cathode of the diode 8 and the cathode of the thyristor of the optocoupler 9, the anode of the thyristor is connected to the winding of the relay 6. The anode of the diode 8 is connected to the capacitor 10 and the cathode of the LED of the optocoupler 9. The anode of the diode 11 is connected to winding relay 7. The negative terminal of the power source 1 is connected to the cathode of the diode 11, the anode of the LED of the optocoupler 9, the second terminal of the capacitor 10 and a resistor. 513 signals of contacts 12 and 13 of a polarized relay indicate the absence of voltage or phases, and the closure of contacts 12 and 14 indicates the presence of voltage or phases. When monitoring the voltage of a three-phase network, a rectifier assembled, for example, according to Larionov's scheme, can be used as the power source 1. The voltage detector during the control of the voltage of a three-phase network operates as follows. In the initial state, the contact 3 of the polarized relay is open and the contacts 12 and 13 are closed. When the three-phase network is turned on and voltage is applied to the load (not shown), it is necessary to press the 2 Start button. Through the capacitor k, the winding of the relay 7 and the diode 11 passes a current pulse that triggers the relay. By step 3 it closes and connects the alarm to power supply 1. Contacts 12 and It also close, which indicates the presence of a three-phase voltage in the network. Capacitor C is charged before the supply voltage and winding 7 is de-energized. The thyristor of the optocoupler 9 is closed, since the LED of the optocoupler does not light, the anode of the LED is connected to the common wire of source 1, and the cathode through diode 8, the winding of the relay 7 and diode 11 is also connected to the common wire of source 1. The low voltage is of a pulsed nature, equal to zero in the intervals between pulses. At this time, the voltage of the capacitor 4 charge is applied to the opto-9 LED. A positive potential is applied through the resistor 5 to the anode of the LED, and a negative potential through diode 8 to the cathode of the LED. The LED turns on the thyristor of the optocoupler 9 and the final discharge of the capacitor 4 occurs through the winding of the relay 6 and the thyristor of the optocoupler 9. The pulse of the discharge of the capacitor 4 triggers the relay, contact 3 opens, which means that one or several voltage phases disappear. Contacts 12 and 14 are closed, and 12 and 13 are closed, and into the external circuit. a signal is received that one or several voltage phases have disappeared. To restart the detector at a normal three-phase voltage, you must press the Start 2 button. 6 The value of the capacitor capacitance k is chosen, based on the time triggered by the formula, nor the polarized relay, Up-Ue. l. where Up is the fault on the relay coil; power supply voltage; R is the winding resistance; capacitor capacitance 4; the time required to trip the polarized relay; voltage drop on diode 1 1. The magnitude of the resistor 5 is chosen based on the current required for the normal illumination of the LED 9, which ensures a clear turn on of the thyristor. As an optocoupler, for example, a thyristor optocoupler of the AO103 type can be used. The capacitor 10 by its shunting effect protects the LED of the optocoupler 9 from possible interference induced in the common circuit of the voltage detector, thus providing increased noise immunity. At the moments of switching on the protection device, i.e. moments of charge of the capacitor 4, the diode 8 and the capacitor 10 protect the LED of the optocoupler 9 from reverse voltage. When operating from a DC source, the circuit operates in the same way. This voltage detector differs from the known ones in that it allows to increase the noise immunity of the circuit and to control not only the constant voltage on the load, but also the alternating three-phase voltage, while maintaining high reliability and simplicity of circuit construction. Claims A voltage detector comprising a power source and a daisy winding polarized relay connected in series, a capacitor and a diode whose cathode is connected to the negative terminal of the power source, and a resistor, characterized in that, in order to improve noise immunity, it is additionally equipped with an optron, a second a diode and a capacitor, while the positive output of the power source through the closing contact of a polarized relay, shunted by a button, is connected in series with one of you. a resistor and a positive capacitor plate, in parallel with which the first winding of a polarized relay is connected with a series-connected thyristor of the optocoupler in the forward direction, and the second winding of a polarized relay is connected between the negative capacitor plate and the anode of the diode, the cathode of which is connected to the second output of the resistor and the anode the LED of the optocoupler, whose cathode is connected to the anode of the second diode, the cathode of the latter is connected to the negative plate of the capacitor, in addition, the LED of the optocoupler is shunted into condenser. Sources of information taken into account in the examination 1, USSR Author's Certificate, No. 335765, class, H 01 H 3/2 +, 1969. I 2. USSR Author's Certificate, No. 383151, class. H 02 H 3/24, 1971. 3. USSR author's certificate №, cl. G 01 R 9/16, 1970.