RU2777728C1 - High-voltage switching apparatus - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention relates to the field of instrumentation and can be used for high-voltage switching. High-voltage switching apparatus containing N series-connected relays and N control transformers is characterised by the primary being made in the form of a segment of a high-voltage cable passed consecutively through the cores of all N control transformers. The control of the apparatus is characterised by the fact that during connection, an opening signal is sent to the input of the control amplifier in the form of a pulse sequence with a duty cycle of two (meander), the pulse sequence arising on the secondary windings of the control transformers is directed to the relay control circuits, and the DC voltage arising at the outputs thereof is supplied to the relay control coils in order to achieve closure of the relay contacts and further transmission of current from the input to the load connected to the output.

EFFECT: increase the speed of the apparatus and increase reliability due to the reduced amount of elements thereof.

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Description

The invention relates to the field of instrumentation and can be used for switching high voltage. The proposed high-voltage switch can be used in control circuits of high-voltage equipment, including high-voltage test facilities and devices, in power supply and control circuits of beam research and technological installations, as well as in power supply systems for microwave generator devices, etc.

A high-voltage switch is known from the prior art (see [1] copyright certificate SU 801129 A1), containing a switch of series-connected reed switches separated from the control winding by high-voltage insulation.

A high-voltage switch is known from the prior art (see [2] copyright certificate SU 1737550) containing series-connected reed switches separated from the control winding by high-voltage insulation. To improve the operation of the key, ferrite rods are installed in the insulation. Reed switches control a high-voltage thyristor.

In the switch circuits described in [1] and [2] sources, N series-connected reed switches are used, separated from the control winding by high-voltage insulation.

The disadvantage of such a scheme is the difficulty of ensuring high reliability of switching the key at a voltage of more than 10-15 kV, since at such a voltage the insulation layer is too large.

A high-voltage switch is known from the prior art (see [3] copyright certificate SU 1734203 A1), containing N series-connected transistors, to the input (base) of which N control circuits are connected. Turning on (opening) the key is carried out by applying a control signal through high-voltage optocouplers to the control circuits. The control circuits are powered by capacitors, which are recharged while the key is in the closed state. When the key is turned on (opened), the supply capacitors are gradually discharged and the key must be closed until the capacitors are completely discharged.

The disadvantage of this scheme is the impossibility of keeping the key in the open state for a long time.

Known patent [4] - US 6900557 B1, publ. 05/31/2005, which discloses a high-voltage transistor switch containing N series-connected transistors and N control transformers, the output of the key control circuit is connected to the base of each transistor, the second output of the key control circuit is connected to the emitter of each transistor, the inputs of the key control circuit are connected to the secondary winding of the transformer, the control signal generator circuit is connected to the primary winding of the control transformers.

The difference between the claimed device and that disclosed in [4] is that the control transformers are connected according to the current transformer circuit, and the primary winding, common to all N transformers, is made in the form of a high-voltage cable segment.

It should also be noted that a high-voltage transistor switch is known [5] - (RU 69685 U1, publ.: 12/27/2007), in which the control transformers are connected according to the current transformer circuit (TT1-TTn), and the primary winding is made common for all N transformers .

Despite the fact that simplification is provided for it, the use of a high-voltage cable segment is not provided as a common primary winding of current transformers. This means that in the design of these transformers it is necessary to use a large amount of insulating materials, since all the secondary windings of the transformers are under high voltage, different in magnitude for each transformer. This design of the transformer leads to a significant increase in the leakage inductance, which in turn leads to a distortion of the shape of the pulses - a delay in the fronts of the pulses. Thus, the design of control transformers given in this patent will not provide a significant increase in speed and increase in reliability.

Also, in the source of information [6] - SU 510064 A1, publ.: 09/27/1996, the execution of a common primary winding in the form of a high-voltage cable segment is disclosed.

But the technical problem there is that the magnetic circuits put on the cables, which are the primary winding of thyristor control transformers, significantly (hundreds of times, if not thousands) increase the cable inductance. Indeed, the upstream and downstream inductances are subtracted from each other. But due to the inevitable asymmetry in the location of the cable branches and the location of the surrounding magnetic circuits, these inductances will not be equal to each other and full compensation will not be possible to achieve.

As a result, the inductance of the control cable from the side of the control pulse generator 5 as a result of the installation of these magnetic circuits will increase significantly (perhaps by 1 or 2 orders of magnitude), which will lead to an increase in the duration of the fronts of the control pulses, reduce speed and reliability.

In addition, the scheme described in [6] cannot be used to control the relay, because it is used to open the thyristors with short pulses and cannot generate the DC voltage required to operate the relay.

The closest analogue to the claimed invention in terms of the set of features taken as a prototype is a high-voltage transistor switch (see [7] - RU 2339158 C2, publ.: 20.11.2008).

The key circuit described in the patent uses N transistor switches connected in series. The inputs (gates) of the transistor switches are connected to the secondary windings of the control transformer through matching and protective elements. Such a circuit allows for galvanic isolation of control circuits and high-voltage circuits, as well as for better simultaneity of turning on and off the switch transistors.

Instead of transistor switches, reed relays can be used.

The technical problem of the analogue from the patent [7] is the high complexity and, consequently, the high cost of manufacturing a control transformer, since its design provides for the presence of N secondary windings, each of which is under a different high voltage, which requires the use of a large amount of high-voltage insulating materials . Such a transformer has an increased stray field, as a result of which the shape of the control pulses can be distorted, which causes non-simultaneous operation of the keys, which in turn reduces the speed and reduces the reliability of the key.

The technical challenge facing the invention is to eliminate the shortcomings of the prototype and other known solutions.

The technical result of the claimed invention is an increase in speed, an increase in reliability, a decrease in the number of key elements and a decrease in the size of a high-voltage switch.

The specified task and technical result are achieved due to the fact that a high-voltage switching device is claimed, containing N series-connected relays, including reed relays, and N control transformers, characterized in that, in order to increase reliability and increase speed, control transformers are connected according to the transformer circuit current, and the primary winding is made in the form of a piece of high-voltage cable threaded in series through the cores of all N control transformers.

The contacts of each relay can be shunted with a balancing resistor.

The output of the key control circuit can be connected to the control winding of each relay, which converts the alternating voltage from the secondary winding of the transformer into a constant one.

The inputs of the key control circuit can be connected to the secondary winding of the transformer, the control signal generator circuit is connected to the primary winding of the control transformers.

To the primary winding of the control transformers, which is common to all N transformers, a limiting resistor and a control signal amplifier can be connected, which are a control signal generator circuit.

The output of the key control circuit can be connected to the control winding of each relay, which converts the alternating voltage from the secondary winding of the transformer into a constant one, and the inputs of the key control circuit are connected to the secondary winding of the transformer, and the control signal generator circuit is connected to the primary winding of the control transformers.

The use of the proposed high-voltage key, unlike the prototype, N relays (including reed relays), allows you to increase reliability and reduce the number of key elements, since the operating voltage of the relay is much higher than the operating voltage of the transistor. Reducing the number of elements leads to an increase in reliability, a reduction in size and a decrease in the cost of the device.

In addition, the use of a piece of high-voltage cable as the primary winding of current transformers, threaded in series through the cores of all control transformers, makes it possible to significantly simplify the design of the transformer, which also leads to an increase in reliability and a reduction in the size of the product. In addition, current transformers have a low stray field, which leads to the fact that the control signals of all transformers have the same shape, the relays operate simultaneously, which leads to an increase in speed and an increase in the reliability of the device.

Brief description of the drawings

Figure 1 shows a schematic diagram of a high-voltage switching device.

Figure 2 shows comparative photographs of the dimensions of the products of the control transformer for the key, made: (left view - according to the prototype [7], where the transformer has a primary winding and four secondary windings with high-voltage insulation; right view - the declared current transformer having a primary winding in in the form of a piece of high-voltage cable and the secondary winding).

Figure 3 shows an example of the use of a switching device in the circuit of a push-pull pulse modulator for powering a microwave generating device - a magnetron.

Figure 4 shows an example of the use of a switching device in a setup for testing high-voltage cables with a bipolar voltage of extra low frequency (VLF).

In the drawings: 1 - control signal amplifier; 2 - limiting resistor; 3 - secondary winding of the control transformer; 4 - relay control circuit; 5 - relay control coil; 6 - relay contacts; 7 - equalizing resistor, 8 - control circuit, 9 - magnetron, 10 - charging resistor for charging the storage capacitor, 11 - storage capacitor for supplying the magnetron with a pulsed current, 12 - high voltage power supply of the installation, 12.1 - source of positive test voltage, 12.2 - source of negative test voltage, 13 - magnetron filament power supply, 14.1, 14.2 - discharge diodes for removing residual charge from the cable capacitance before connecting the cable to the opposite polarity of the test voltage, 15 - cable capacitance discharge current limiting inductance, 16 - cable, 17.1 - high-voltage switch for turning on the magnetron, 17.2 - high-voltage switch for forming the trailing edge of the magnetron pulse, 17.3 - high-voltage switch of the positive test voltage, 17.4 - high-voltage switch of the negative test voltage.

Implementation of the invention

Figure 1 shows a diagram of a high-voltage switching device. The high-voltage switch contains N relays (6) connected in series, N control transformers, the contacts of each relay (6) are shunted by an equalizing resistor (7). The outputs of the relay control circuit (4) are connected to the control coil of each relay (5), which converts the alternating voltage from the secondary winding of the transformer into a direct voltage. The inputs of the relay control circuit are connected to the secondary winding (3) of the control transformer. A limiting resistor (2) and a control signal amplifier (1) are connected to the primary winding of the control transformers, which is common to all N transformers. The second end of the primary winding is connected to a common wire.

All N control transformers are connected according to the current transformer circuit, which makes it possible to use a piece of high-voltage cable passing through the cores of all transformers as the primary winding of all N transformers. This makes it possible to significantly simplify the design of transformers due to the absence of high-voltage insulating materials in the design of the transformer, since the function of high-voltage insulation is performed by the primary winding of the transformer made from a piece of high-voltage cable. Such a design of transformers will lead to a reduction in their size, an increase in their reliability and a decrease in their cost.

Achieving the possibility of reducing the size can be clearly seen from the practical example in Fig.2, which shows photographs of: (left) - control transformer for the key described in [7]. The transformer has a primary winding and four secondary windings with high voltage insulation; (right) - declared current transformer, which has a primary winding in the form of a piece of high-voltage cable and a secondary winding.

The switch control circuit uses both half-waves of the control voltage from the secondary winding of the transformer to control the relay, which leads to an increase in the speed of the switch.

As a control signal, not a sinusoidal signal, but a rectangular one (meander) was used, which makes it possible to reduce the ripple of the control voltage at the output of the relay control circuit, which also leads to an increase in the speed of the switch and an increase in reliability.

The device works as follows.

When the switch is turned on (opened), an opening signal is sent to the input of the control amplifier in the form of a sequence of pulses with a duty cycle of two (meander). A pulse train also appears on the secondary windings (3) of the control transformers. These pulses are sent to the control circuits of the relay (4) and a constant voltage appears at their outputs, which is supplied to the control coils (5) of the relay, which leads to the closing of the relay contacts and the current from the INPUT terminal flows to the load connected to the OUTPUT terminal. When the switch is turned off (closed), the signal at the input of the control amplifier is turned off.

The signal on the secondary windings (3) of the control transformers also becomes zero. The voltage at the output of the relay control circuit begins to decrease, and when the relay off voltage is reached, the switch will close.

Since a meander is used as a control signal, the ripple value at the output of the relay control circuit (4) is small, which makes it possible to select smoothing elements in the relay control circuit with a small time constant, which is close to the relay actuation time (5). Thus, the speed of the described high-voltage switch is determined mainly by the speed of the relay.

An example of the practical use of the proposed high-voltage switch is a push-pull pulse modulator for powering a microwave generating device - a magnetron. Its circuit is shown in Fig.3, where 17.1 - high-voltage switch is used to turn on the magnetron, 17.2 - high-voltage switch is used to form the trailing edge of the magnetron pulse, connected in series and connected to the control circuit 8.

This example contains two series-connected relays and two control transformers, where the primary winding is made in the form of a piece of high-voltage cable common to all transformers.

The control circuit of the modulator 8 controls the switches 17.1, 17.2. The magnetron 9 is connected to the power supply 12 of the installation with high voltage and is connected between 17.1 and 17.2 to the power supply of the filament of the magnetron 13. In this case, the switch 17.1 is connected between the charging resistor 10 to charge the storage capacitor and the storage capacitor 11 to power the magnetron with a pulsed current.

Such a pulse modulator is used to generate powerful microwave radio pulses, for example, in radar stations. The pulse is generated at the moment the switch 17.1 is activated and the negative supply voltage is applied to the magnetron grid 9. The trailing edge of the radiation pulse is formed when the switch 17.1 is turned off and the switch 17.2 is turned on.

Another example of the use of the proposed high-voltage switch can be an installation for testing high-voltage cables with a bipolar voltage of extra low frequency (VLF). A diagram of such an installation is shown in Fig.4, where 17.3 is a high-voltage switch of a positive test voltage, 17.4 is a high-voltage switch of a negative test voltage, are also connected in series and connected to the control circuit 8.

This example also contains two series-connected relays and two control transformers, where the primary winding is made in the form of a piece of high-voltage cable common to all transformers.

The VLF test setup generates a high cosine-rectangular voltage of alternately positive and negative polarity of ultra-low frequency (0.1 Hz) on the tested cable 16 through inductance 15.

To do this, the circuit uses sources of positive test voltage 12.1 and negative test voltage 12.2, each of which passes through the switches 17.3 and 17.4. respectively, and then through the discharge diodes 14.1 and 14.2, respectively, to remove the residual charge from the cable capacitance before switching on the cable to the opposite polarity of the test voltage. The inductance 15 serves to limit the discharge current of the cable capacitance.

Claims (3)

1. A high-voltage switching device containing N series-connected relays, including reed relays, and N control transformers, characterized in that the control transformers are connected according to the current transformer circuit, and the primary winding is made in the form of a high-voltage cable segment, threaded in series through the cores of all N control transformers, the second end of the primary winding is connected to a common wire, and the switch control circuit uses both half-waves of the control voltage from the secondary winding of the transformer to control the relay, where a rectangular (meander) is used as a control signal. 2. The device according to claim 1, characterized in that the contacts of each relay are shunted by an equalizing resistor. 3. The device according to claim 1, characterized in that the output of the relay control circuit is connected to the control winding of each relay, which converts the alternating voltage from the secondary winding of the transformer into a constant one, and the inputs of the key control circuit are connected to the secondary winding of the transformer, and to the primary winding of the control transformers, a control signal amplifier circuit is connected.

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