RU2402854C1 - Device for electronic equipment protection against hv pulse disturbances - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: device includes two protection stages: that of a semi-conductor voltage limiter (SVL) and that of a varistor. In case of SVL disruption the thyristor key control circuit begins counting the amount of electricity having passed through SVL after disruption; in case the preset threshold is exceeded the circuit, with the help of the thyristor key, actuates the varistor which conducts the current caused by the disturbance pulse and makes SVL dead, thus preventing its burning. The varistor is thermally connected to a circuit breaker; in case of the varistor heating to a temperature in excess of the threshold value predefined the circuit breaker is actuated and trips supply of mains voltage to the load and to the protection device. ^ EFFECT: increased reliability and expansion of functional capabilities. ^ 1 dwg

Description

The invention relates to the field of electrical engineering, and more specifically to devices for protecting electronic equipment and electrical equipment from overvoltages in the power supply network.

A device for protection against surge surges (Zaglyadin N. Radio equipment protection node. Radio Amateur magazine, 1996, No. 7, p.20), containing a network thermal fuse, a chain of semiconductor voltage limiters connected in parallel with the load with a measuring resistor connected in series with them (acting as a current sensor), a thyristor switch connected to the load with a control input, and the connection point of the voltage limiter and measuring resistor is connected to the control th input of the thyristor key. The thyristor switch turns on when the set voltage is reached on the measuring resistor and forcibly fuses the fuse included in the protected network, disconnecting the load. This device is selected as a prototype.

This prototype device protects the load from high-voltage impulse noise, however, it has significant drawbacks: the device is already triggered by a short duration of high-voltage interference pulses (10-20 microseconds), while the fuse blows forcefully and disconnects the load from the mains, which in some cases is unacceptable.

The proposed device allows to eliminate these disadvantages.

Thus, the technical result of the invention is to expand the functionality of the protection device and increase the reliability of the protection device.

The essence of the invention lies in the fact that the device for protecting electronic equipment from high-voltage impulse noise contains the first and second input terminals, the first and second output terminals, a circuit breaker, voltage limiter, current sensor, thyristor switch with a control input, and the power supply is connected to the first and a second input terminal, a load is connected between the output first and second terminals, a circuit breaker is connected between the first input and output terminals and, a thyristor switch with a control input and a chain of series-connected voltage limiter and current sensor are connected between the first and second output terminals in parallel with the load, the connection point of the voltage limiter and current sensor is connected to the control input of the thyristor switch (distinguishing features follow), the proposed device contains also a high power varistor and a thyristor key control circuit, the circuit breaker has a means for turning off when heated, and the housing in the variable resistor is thermally coupled to the circuit breaker, a varistor connected between the output terminal and the first wrench thyristor and a thyristor control circuit connected between the control input of the thyristor and the point of the key compound of the voltage limiter and a current sensor.

The essence of the invention also lies in the fact that the specified thyristor switch control circuit contains an integrating unit that determines the amount of electricity flowing through the voltage limiter from the moment of its breakdown.

The invention also lies in the fact that the specified integrating node is an RC chain.

The invention will be clear from the following description, which is illustrated in the drawing.

The drawing indicates:

1 - Electric network;

2 - the first input terminal;

3 - the first output terminal;

4 - second input terminal;

5 - second output terminal;

6 - load (electronic equipment);

7 - circuit breaker;

8 - varistor;

9 - thermal connection of the circuit breaker and the varistor (shown by a dotted line);

10 - voltage limiter;

11 - thyristor key;

12 - control input of the thyristor key;

13 is a thyristor key control circuit;

14 - current sensor;

15 - connection point of the voltage limiter and current sensor.

The device for protecting electronic equipment from high-voltage impulse noise is connected to the power supply network 1 (drawing), and the power supply voltage is supplied between the first input terminal 2 and the second input terminal 4. Load 6 (electronic equipment) is connected between the first output terminal 3 and the second output terminal 5. A circuit breaker 7 is connected between the first input terminal 2 and the first output terminal 3. The circuit breaker is, for example, a device with a bimetallic contact, which and heating of the varistor breaks the electrical circuit powering the load. The circuit breaker can also be made using a thermistor with a control circuit and a key element.

Between the terminals 3 and 5 parallel to the load 6 is connected a chain of series-connected voltage limiter 10 and current sensor 14, which in this particular case is made using a measuring resistor 14.

As a voltage limiter 10, a semiconductor voltage limiter (PON) is used with a small differential resistance and a sufficiently high speed. PON provides the first stage of load protection against high-voltage interference pulses.

Between the terminals 3 and 5 parallel to the load 6 is also connected a chain of series-connected varistor 8 and thyristor switch 11.

The varistor is also a voltage limiter, but, unlike PON, it has a lower voltage limiting threshold, lower speed, but greater differential resistance and has a higher absorption capacity. The varistor is the second step in protecting the load from a high voltage interference pulse.

The connection point 15 of the voltage limiter 10 and the current sensor 14 is connected to the control circuit 13 of the thyristor switch 11. The control circuit 13 of the thyristor switch 1 in the preferred embodiment of the invention is implemented as an integrating unit that determines the amount of electricity flowing through the voltage limiter 10 from the moment of its breakdown which occurs if the high-voltage interference pulse exceeds the breakdown threshold voltage of the voltage limiter 10. The control circuit can also be made in the form of a threshold element with an integrating unit (digital integrator circuit with a comparison value at its output with a predetermined threshold value and the like).

In a preferred embodiment of the invention, said integrating unit may be implemented in the form of an analog circuit - an RC circuit, wherein the resistor of the circuit is connected to the connection point of the PON and the current sensor, the second output of the resistor of the circuit is connected to the capacitor of the circuit, the second output of which is connected to ground.

The control circuit 13 of the thyristor switch 11 is connected to its control input 12.

The varistor 8 is made so that it has a thermal connection with the circuit breaker 7 (in the drawing, this thermal connection is shown by a dashed line).

A device for protecting electronic equipment from high-voltage impulse noise works as follows.

In the normal mode, in the absence of high-voltage interference pulses, the voltage limiter 10 is closed, the current through the current sensor 14 does not flow, there is no voltage at point 15, so the control circuit 13 does not provide a signal to the control input 12 of the thyristor switch 11, which is in the passive state (not lit ) and does not pass current through itself, so the circuit breaker is in normal mode, open, and load 6 is connected to the power supply network 1.

When a high-voltage interference pulse arriving from the network 1 exceeds a predetermined limit, the voltage limiter 10 breaks through it and the current sensor 14 flows, while the voltage at the load 6 is limited to the breakdown voltage of the voltage limiter 10 (first protection circuit). And in the control circuit 13, an integration unit starts to work, which counts (in an analogous way) the amount of electricity flowing through the voltage limiter 10 from the moment of its breakdown.

Gradually, if the interference pulse does not end, the voltage at the control input 12 of the thyristor switch 11 rises and upon reaching a predetermined threshold value (depending on the selected parameters of the control circuit 13) turns on the thyristor switch 11 in the current transmission mode, and this current passes through varistor 8, heating him. Thus, the second protection circuit on the varistor 8 is turned on, and the current flowing through the voltage limiter 10 now flows through the varistor 8. If, however, the interference pulse does not end, then the varistor 8 heats up so much that it heats and turns off the circuit breaker 7 due to thermal communication 9 varistor 8 with a circuit breaker 7. In this case, the load 6 is disconnected from the network 1. The mechanism for turning off the circuit breaker during heating is that it disconnects the mains voltage from the load and the protection unit, when The varistor temperature reaches the setpoint.

So, when energy is released on the voltage limiter that exceeds a predetermined threshold, the second protection circuit (varistor) is turned on, and the voltage limiter is de-energized. The varistor is also protected in the proposed device, since when it is heated above the set value, the circuit breaker opens, which disconnects the protection device and the load from the power supply.

Thus, the proposed protection device when exposed to a high-voltage interference pulse protects the load, voltage limiter and varistor from damage. The functionality of the protection device is expanded and the reliability of the electronic device and the proposed protection device is increased.

The present invention can be implemented, since all the necessary elements and technologies are known and available.

Claims (3)

1. A device for protecting electronic equipment from high-voltage impulse noise, comprising the first and second input terminals, the first and second output terminals, a circuit breaker, a voltage limiter, a current sensor, a thyristor switch with a control input, the power supply being connected to the first and second input terminals, the load is connected between the output first and second terminals, a circuit breaker is connected between the first input and output terminals, a thyristor switch with a control input and a chain of sequentially connected voltage limiter and current sensor are connected between the first and second output terminals in parallel with the load, the connection point of the voltage limiter and current sensor is connected to the control input of the thyristor switch, characterized in that it contains a high power varistor and a thyristor switch control circuit, the circuit breaker has means to turn off when heated, and the varistor housing is in thermal communication with the circuit breaker, the varistor is connected between the first output th terminal thyristor and a key, and a thyristor control circuit connected between the control input of the thyristor and the point of the key compound of the voltage limiter and a current sensor. 2. The device according to claim 1, characterized in that the thyristor switch control circuit contains an integrating unit that determines the amount of electricity flowing through the voltage limiter from the moment its breakdown began. 3. The device according to claim 2, characterized in that the said integrating node is an RC chain.