RU2579529C1 - Device for controlling thyristors of bridge circuit of device for testing electric meters - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: disclosed device feature is that charging current switches used thyristors, and control circuit switching on of thyristors of charging and discharge circuits with short pulses is based on serial connection connected with synchronizing voltage comparator, two series-connected inverters, outputs of which via two differentiating RC-circuits are connected to two pulse power amplifiers with transformer output, connected to output of first differentiating circuit, and third pulse power amplifier connected to output of second differentiating circuit, and secondary isolated between winding output of pulse transformers are connected to control inputs of appropriate thyristor bridge circuit.

EFFECT: technical result is simplification of thyristor control device.

1 cl, 3 dwg

Description

The invention relates to the field of measuring electrical engineering and can be used to assess the suitability of newly developed electricity meters from uncontrolled selection of electricity from power networks.

Known devices for checking electricity meters [1-6].

The closest analogue to the claimed technical solution (prototype) is a "Device for checking induction meters of electricity metering" according to RF Patent No. 2521307, publ. in No. 18 dated 06/27/2014 [5], which contains storage capacitors charged with intermittent current at an increased interrupt frequency and smoothly discharged back into the network, as well as transistor current interrupting and switching circuits for the smooth discharge of storage capacitors, characterized in that it includes two parallel connected to the network after the tested electric meter circuits from series-connected storage capacitor and bidirectional transistor switch, forming a bridge circuit so that the storage capacitor is not The main circuit is connected to the phase conductor of the network, and the capacitor of the second circuit is connected to the neutral conductor of the network, and a triac and an inductor are connected in series to the diagonal of this bridge circuit, and transistors of bidirectional transistor switches of these circuits and a triac are connected to the corresponding outputs of the transistor control unit and triac , the synchronization of which is carried out from the network.

A disadvantage of the known device is the increased complexity of the control device for turning on and off the transistor switches of the bridge circuit, which is associated with the fulfillment of the prerequisite according to which the inclusion of the thyristor (triac) of the diagonal circuit of the bridge circuit should only follow after the transistor switches of the charging circuits with storage capacitors are completely closed at the end of the first and third quarters of the mains voltage period. In addition, when controlling transistor switches, sufficiently long pulses (of the order of 5 ms for a standard network with a frequency of 50 Hz) should be generated, which increases the energy loss in the circuit. The latter also grow when using transistors as switches, which require cooling at a sufficiently high power of the device.

These shortcomings are eliminated in the claimed technical solution.

The objectives of the invention are to simplify the thyristor control device when replacing the transistors switching the charge circuits of the storage capacitors of the bridge circuit with thyristors, the inclusion of which is carried out by short pulses, which reduces energy losses in the control device.

These goals are achieved in the inventive thyristor control device of the bridge circuit of the device for checking electric meters, containing a bridge circuit of two storage capacitors in parallel with the charge source circuit with unidirectional charge current switches and a diagonal discharge circuit from the thyristor, as well as a control device for charge current and thyristor switches discharge circuit of a bridge circuit, characterized in that thyristors are used as charge current switches, and the circuit has Short pulses by turning on the thyristors of the charging and discharge circuits are made on the basis of a series connection of a comparator connected to the synchronizing voltage of the network, two inverters connected in series, the outputs of which are connected through two differentiating RC circuits to two pulse power amplifiers with transformer outputs connected to the output of the first differentiating circuit , and one connected to the output of the second differentiating circuit, and the secondary windings of the output pulse are decoupled among themselves transformers are connected to the control inputs of the corresponding thyristors of the bridge circuit.

Achieving these goals is explained by the fact that replacing the transistor switches of the charging current with thyristors reduces electrical losses in the device, since the thyristors are turned on by short pulses, tied in time to the phases of the mains voltage φ ₁ = 2πn - for two thyristors in the charge chains of storage capacitors and φ ₂ = π (2n + 1) - for the thyristor of the diagonal discharge circuit. In addition, the use of thyristors in the charging circuits of a bridge circuit instead of transistors leads to automatic locking of the thyristors when the current flowing through them decreases to a very small level or after removing the voltage acting between their cathode and anode. This allows you to use only one comparator synchronized by the mains voltage in the thyristor control device. The use of short pulses to control the inclusion of thyristors simplifies the design of output transformers of pulse power amplifiers.

The scheme of the claimed device is given in Fig. 1, a variant of the construction of pulsed power amplifiers is shown in Fig. 2a in fig. Figure 3 shows graphs of the voltage (solid line) acting on the terminals of the meter under test (on its voltage winding) and the current flowing through the current winding of the meter (dashed line), for example, of the induction type.

Schematic diagram of the device (Fig. 1) contains the following elements and nodes:

1 - the first storage capacitor with a capacity of C _H ,

2 - the first thyristor of the charge circuit,

3 - the second thyristor of the charge circuit,

4 - the second storage capacitor with a capacity of C _H ,

5 - thyristor of the discharge circuit of a bridge circuit included in its diagonal,

6, 7 and 8 - output pulse transformers of control circuits of thyristors 2, 3 and 5, for example, type TOT62,

9, 10 and 11 - pulse power amplifiers,

12 - step-down transformer mains voltage (for example, to a voltage of 6.3 V),

13 - a comparator (for example, on a chip type K521CA3A),

RC - the first and second differentiating circuits (RC ≈0.1 ms),

14 and 15, respectively, the first and second inverters (for example, 1/2 IC type K555LA3),

16 - a secondary power source for voltage +5 V and +15 V, which includes a step-down transformer 12.

A variant of a pulsed power amplifier (Fig. 2) includes:

17 - n-p-n-transistor, for example, type 2T325V,

18 - one-shot, for example, on the IC type K1006VI1,

19 and 20 - a resistor and a capacitor of a timing circuit of a single vibrator 18 (for a time of 0.5 ms),

21 is an intermediate pulse transformer, for example, type TOT2,

22 - output n-p-n-transistor of medium power, for example, type KT819A,

23 - absorbing extracurrents of the primary winding of the transformer diode, for example, type D312. The output of this amplifier through a pulse transformer, for example, of the TOT62 type, is connected to the control electrode of the corresponding thyristor of the bridge circuit via a limiting resistor ..

In fig. 3, the solid line shows the type of voltage u (t) acting on the voltage meter winding, and the dashed line shows the charge current i _ZAR (t) and the discharge current i _RAT (t) in the storage capacitors 1 and 4. Note that these capacitors are charged connected through open thyristors 2 and 3 to the network source in parallel, and when discharged, they are turned on by thyristor 5 in series (with thyristors 2 and 3 already closed).

Consider the operation of the claimed device.

When an alternating voltage is lowered by the transformer 12 to the input of the comparator 13, a meander pulse signal is generated at its output with a duty factor of two, inverted with respect to the positive half-waves of the mains sinusoidal voltage. At the output of two series-connected inverters 14 and 15, positive and negative meander signals are generated, which are then differentiated by the first and second RC circuits. Positive pulses of differentiated meander pulses act on the inputs of pulse power amplifiers (Fig. 2) 9, 10 and 11 with transformer outputs. The secondary windings of these transformers 6, 7 and 8 decoupled from each other through limiting resistors are connected to the “control electrode - cathode” junctions of the thyristors 2, 3, and 5 of the bridge circuit, respectively.

At the phases of the mains voltage φ ₁ = 2πn (n is an arbitrary integer), the thyristors 2 and 3 of the charging circuits of the bridge circuit open with short pulses, and the storage capacitors 1 and 4 are charged over a quarter of the period T of the mains voltage to the amplitude value U _O ≈300 V (at current network voltage 220 V). After the charge of these capacitors, thyristors 2 and 3 are automatically closed, since the charging current tends to zero, as can be seen in Fig. 3. At phases of the mains voltage φ ₂ = π (2n + 1), the thyristor 5 of the discharge circuit opens with a short pulse, and the storage capacitors 1 and 4 become connected in series and, therefore, are discharged back to the network source at an initial voltage of 2U _O ≈600 V. Since the power line and the substation transformer are inductive, the discharge current has the form of a quasi-sinusoidal pulse of large amplitude, the value of which is determined by the very small internal resistance of the mains voltage source, for example, of the order ka 0.3 ... 1 Ohm, as well as a duration Δt of _{discharge of the} discharge pulse (see Fig. 3), due to the inductance of the network source and the conductors of the discharge circuit of the bridge circuit. In this case, the maximum voltage acting on the voltage winding of the tested electric meter, connected in series with the claimed device to the network, is slightly less than 2U _O , as can be seen in Fig. 3, due to small losses inside the device. These losses are the sum of the voltage drop across the cathode-anode gap of thyristor 5 and the known quality of the storage capacitors 1 and 4 used (therefore, pulse capacitors, for example, type K75-1, must be used in the device).

, определяет и энергию W, возвращаемую обратно в сеть при разряде последовательно соединенных накопительных конденсаторов 1 и 4. Нетрудно понять, что величина электрического заряда q=2C_HU_O определяется интегралом от мгновенных значений тока заряда и разряда за время действия этих токов. Это можно записать в виде интегрального равенства:If, in a first approximation, neglected losses in the bridge circuit, it can be argued that the charge energy in parallel connected storage capacitors 1 and 4, equal to $$W=C_{\mathrm{<figure-callout\; id="2"\; label="N\; U\; O"\; filenames="00000006.png,00000007.png"\; state="\{\{state\}\}">N\; </figure-callout>}}{U}_O^{}{}_2^{}$$

also determines the energy W returned back to the network during the discharge of series-connected storage capacitors 1 and 4. It is easy to understand that the electric charge q = 2C _H U _O is determined by the integral of the instantaneous values of the charge and discharge current during the action of these currents. This can be written as integral equality:

that is, the area of the figures covered by dashed lines in Fig. 3 are equal. It is clear that the average charge current I _{ZAR.S.R of} storage capacitors is significantly less than the average current of their discharge I _SZR.SR , because T / 2 >> Δt _SIZ . In the time intervals T / 4 ≤ t ≤ T / 2 and [(T / 2) + Δt _SIT ] ≤ t ≤ T, there are no currents in the storage capacitors, as can be seen in Fig. 3. Note that if the electric meter took into account exactly the amount of electricity passing through it to the load in which this electricity does useful work, then connecting the inventive circuit to the network through such an electric meter would not lead to a change in readings during its operation. And therefore, such a device could not be used to “rewind” the readings of the electric meter, which should be taken into account by the developers of electric meters protected from theft of electricity.

However, modern electric meters, for example, of the induction type, work on the basis of integration over the operating time ΔT of the connected active load PRODUCING the instantaneous value of the load current i _N (t) flowing through the current winding of the meter to the instantaneous voltage u (t) applied to the meter's voltage winding so that the energy W _Н consumed by the active load, taken into account by the electric meter, is determined from the expression:

where P is the average power dissipated in the applied active load.

To estimate the energy metering in the forward direction by the counter in expression (2), instead of the current i _Н (t), substitute the value of the charging current i _ZAP (t), and when discharging, the value of the current i _SIT (t).

In general, the integral of the product of functions of one variable is not equal to the product of the integrals of each function with respect to this variable, therefore, strictly speaking, integrals (as a common factor) specified in (1) and equal to each other cannot be taken out of the sign of integral (2) so that they can be reduced by showing clearly that the inequality actually holds:

In the circuit of a pulsed power amplifier (Fig. 2), you can select a timing circuit connected to the terminals 6 and 7 of the K1006VI1 microcircuit with a time constant of the order of 0.5 ms (resistor 1.5 kOhm, capacitor 0.33 μF). The voltage at the transformer output winding should be about 4 V with a thyristor turn-on current of about 0.3 A. The resistance in the thyristor control electrode circuit is 2 ... 7 Ohms (including the active resistance of the transformer output winding), depending on the type of thyristor used.

The proposal should be recommended to the developers of electric meters to test their insensitivity to the "unwinding" of the readings of the consumed electricity. An example of such a counter was proposed in [7].

Literature

1. Smaller O.F. Device for checking the operation of single-phase induction electric meters. Patent No. 2474825, Publ. in the bull. No. 4 dated 02/10/2013;

2. Smaller O.F. Bridge device for checking electric meters of active energy of induction type. Patent No. 2522706, publ. in No. 20 of 07.20.2014;

3. Smaller O.F. Device for monitoring electricity meters. Patent No. 2521782, publ. No. 19 dated 07/10/2014;

4. Smaller O.F. A device for studying the operation of induction electric meters. Patent No. 2523109, publ. in No. 20 of 07/20/2014.

5. Smaller O.F. Device for checking induction electricity meters. Patent No. 2521307, publ. No. 18 dated 06/27/14 (prototype);

6. Smaller O.F. Device for checking induction electric meters. Patent No. 2532861, publ. in No. 31 of November 10, 2014;

7. Smaller O.F. Electricity metering device. Patent No. 2521767, publ. No. 19 dated 07/10/2014.

Patent Search Data

RU 2338217 C1, 11/10/2008. RU 2181894 C1, 04/27/2002. RU 2190859 C2, 10.10.2002. RU 2178892 C2, 01.27.2002. SU 1781628 A1, 12/15/1992. SU 1780022 A1, 12/07/1992. SU 1422199 A1, 09/07/1988. US 7692421 B2, April 6, 2010. US 6362745 B1, 03/26/2002. EP 1065508 A2, 01/03/2001.

Claims (1)

A thyristor control device for a bridge circuit of a meter for checking electric meters, containing a bridge circuit of two storage capacitors with unidirectional charge current commutators and a diagonal discharge circuit from a thyristor, as well as a control device for charge current switches and a thyristor for a discharge circuit of a bridge circuit, characterized in that thyristors are used as charge current switches, and the thyristor on-board control circuit is charged and discharge circuits with short pulses is based on the serial connection of a comparator connected to the synchronizing voltage of the network, two inverters connected in series, the outputs of which are connected through two differentiating RC circuits to two pulsed power amplifiers with transformer outputs connected to the output of the first differentiating circuit, and the third pulsed a power amplifier associated with the output of the second differentiating circuit, and the secondary windings of the output pulse nsformatorov connected to respective control inputs of the thyristors of the bridge circuit.

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