RU2598772C1 - Device for testing inductive electric meters - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to electrical measurement and can be used to assess suitability of newly developed electricity meters against uncontrolled power take-off from power grids. Device for inductive electric meters testing contains in bridge circuit branches storage capacitors of same capacity, which outputs on one side are connected to grid phase and zero conductors, and on the other side is to discharging circuit series-connected thyristor and throttle arranged in bridge diagonal circuit. At that, in series with storage capacitors charging circuits power diodes and thyristors are included connected to grid zero and phase conductors. Charging circuits thyristors are switched on automatically due to resistors connected between said thyristors anode and control electrode and are switched off automatically according to storage capacitors charge in the end of supply voltage periods first quarter. Thyristor discharge circuit in bridge layout diagonal circuit is activated after complete charge of bridge layout storage capacitors in mains voltage second quarter-periods using control device, consisting of connected to bridge circuit diagonal integrating circuit from series-connected controlled limiting resistance and control capacitor, connected to step-down transformer primary winding via dinistor. Said primary winding is shunted by extra current damping diode, and one of transformer three secondary windings is connected to bridge layout discharge circuit thyristor “control electrode-cathode” transition through low-value resistor. Elimination of charging circuits thyristors automatic switching on during discharge circuit thyristor switching on is achieved by means of circuits, including connected to charging circuits “control electrode-cathode” thyristors transitions in series connected stabilizer diode, transformer additional secondary winding and communication capacitor shunted by discharge resistor.

EFFECT: significant simplification of thyristors control device and elimination of secondary power supply source when executing device by single-period charge-discharge scheme of storage capacitors.

1 cl, 6 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 of the claimed technical solution (prototype) is the "Device for checking induction electric meters", patent No. 2532861, publ. No. 31 dated November 10, 2014, which contains storage capacitors charged with intermittent current at an increased interrupt frequency and gradually discharged back to 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 verified electric meter circuits from series-connected storage capacitor and bidirectional transistor switch, forming a bridge circuit so that the storage capacitor first the 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 the transistors of the bi-directional transistor switches of these circuits and the triac are connected to the corresponding outputs of the transistor control unit and the triac, whose synchronization is carried out from the network.

A disadvantage of the known device is the complexity of its transistor control unit and triac. This disadvantage is eliminated in the inventive device.

The objectives of the invention are the significant simplification of the thyristor control device and the exclusion of a secondary power source when the device is designed according to a half-wave charge-discharge circuit of storage capacitors.

These goals are achieved in the inventive device for checking induction electric meters, containing in the branches of the bridge circuit storage capacitors of the same capacity, the terminals of which are connected on the one hand to the phase and zero conductors of the network, and on the other hand, to the series-connected thyristor of the discharge circuit and the inductor installed in a diagonal circuit of a bridge circuit, characterized in that the power diodes and thyristors of the charging circuits are connected in series with the storage capacitors, connected respectively As regards the neutral and phase conductors of the network, the charging circuit thyristors are automatically turned on by the resistors connected between the anode and the control electrode of these thyristors and turn off automatically as the storage capacitors charge at the end of the first quarter of the mains voltage periods, the discharge thyristor in the diagonal circuit of the bridge circuit turns on after the full charge of the storage capacitors of the bridge circuit in the second quarter of the voltage periods of the network using a control device consisting of connected to the diagonal of the bridge circuit of an integrating circuit of series-connected adjustable limiting resistance and a control capacitor connected to the primary winding of the step-down transformer through a dynistor, the specified primary winding being shunted by the damping diode of the extracurrent, and one of the three secondary windings of this transformer is connected to the junction the cathode "of the thyristor of the discharge circuit of the bridge circuit through a low-resistance resistor, with the exception of the automatic inclusion of tiris tori of the charging circuits when the thyristor of the discharge circuit is turned on, it is achieved with the help of circuits, including zener diodes connected in series to the control electrode-cathode junctions of the thyristors of the charging circuits, an additional secondary winding of the transformer and a coupling capacitor shunted by the discharge resistor.

The achievement of the objectives of the invention is due to the replacement of power transistors of the charging circuits of the bridge circuit with a complex control unit circuit requiring the use of a secondary power source, with thyristors of the charging circuits with a relatively simple unit for controlling and controlling the thyristor of the discharge circuit of the bridge circuit. At the same time, a negative impulse to hold these thyristors in a closed state until the thyristor of the discharge circuit starts and slightly lasts after the discharge of the series-connected storage capacitors back to the network is supplied to the control electrodes of the thyristors of the charging circuits. The temporary position of the turn-on thyristor pulse of the discharge circuit within the second quarter of each of the periods of the mains voltage is controlled by changing the time constant of the integrating circuit using an adjustable limiting resistance composed of a constant resistor and a series connected rheostat.

In fig. 1 presents a schematic diagram of the inventive device. In fig. Figures 2-6 are timing diagrams explaining the processes occurring in the circuit.

The inventive device contains the following elements:

1 and 2 - storage capacitors of two branches of the bridge circuit, 3 and 4 - power diodes,

5 and 6 - thyristors of the charging circuits of the bridge circuit,

7 and 8 - including resistors of thyristors of charging circuits,

9 - throttle, forming a discharge pulse,

10 - high-current thyristor of the discharge circuit of the bridge circuit,

11 and 12 is an adjustable limiting resistor of the integrating circuit,

13 - control capacitor integrating circuit

14 - dinistor,

15 - step-down transformer with three separate secondary windings,

16 - diode damping the extracurrent of the primary winding of the transformer,

17 and 18 - zener diodes, anodes connected to the control electrodes of the thyristors of the charging circuits of the bridge circuit,

19 and 20 - discharge resistors in the circuits for holding the thyristors of the charging circuits in a closed state during the discharge of storage capacitors through an open thyristor of the discharge circuit of the bridge circuit,

21 and 22 are coupling capacitors,

23 is a low-impedance delay delay switch thyristor discharge circuit.

The device is connected to the mains through a verified induction meter.

In fig. 2 shows the form of mains voltage, in fig. 3 shows the turning on times of thyristors 5 and 6 of the charging circuits of the bridge circuit when the mains voltage reaches the level of U ₁ , and the moments of their automatic turning off when reaching the amplitude value U _{O of an} alternating voltage of a network of positive polarity (note that turning on of thyristors 5 and 6 does not require the formation of triggering pulses and is carried out automatically), in fig. Figure 4 shows the sequence of pulses including the thyristor 10 of the discharge circuit of the bridge circuit as the storage capacitors 1 and 2 are fully charged almost to the amplitude of the mains voltage U _O , in Fig. Figure 5 shows the process of charging storage capacitors 1 and 2 in the first quarter of the positive half-periods of the mains voltage, as well as their discharge in the second quarter of these half-periods, and Fig. 6 shows a graph of charging and discharge currents in storage capacitors.

Consider the work of the claimed technical solution.

In the first quarter of the positive half-periods of the mains voltage, for example, at phase φ ₁ , that is, at voltage U ₁ = U _O sinφ ₁ , thyristors 5 and 6 are automatically opened by installing resistors 7 and 8, bypassing the anode-control electrode junction of these thyristors, and the storage capacitors 1 and 2 are charged through power diodes 3 and 4 and thyristors 5 and 6 almost to the amplitude of the mains voltage U _O , given the very small time constant of the charge circuits. The voltage U _{1 is} relatively small - about 30 ... 50 V, which provides the required holding currents in automatically opening thyristors 5 and 6, which, in turn, determines the choice of resistors 7 and 8. Since these thyristors are switched on at phases φ ₁ > 0, then the charging current contains the initial pulse and the part that smoothly varies nonmonotonically within the phases φ ₁ ≤φ (t) ≤π / 2, as shown in Fig. 6. Power diodes 3 and 4 prevent the appearance of thyristors 5 and 6 on the control electrodes of high negative potentials with negative half-periods of the network, which could damage these thyristors.

At the phase change section π / 2≤φ (t) ≤φ _{2, the} voltages at the storage capacitors 1 and 2 remain almost unchanged at the level of U _O (about 300 V for a network with an operating voltage of 220 V). If from the control device of the thyristor 10 of the discharge circuit of the bridge circuit an actuation pulse is applied to the control electrode of the latter, correlated with the phase of the alternating voltage of the network φ ₂ , then at that moment the open thyristor 10 with negligible internal resistance (for example, 1 mOhm) storage capacitors 1 and 2 become connected in series to the network with their total voltage of 2U _O. Since at the same time, the voltage in the network is U ₂ <U _O and is counter-directional with respect to the voltage ratio 2U _O , then the series-connected storage capacitors 1 and 2 are discharged back into the network with a maximum initial current equal to I _{P MAX} (2U _O - U ₂ ) / r _C , taking into account the smoothing action of the inductor 9, which excludes an instantaneous increase in the discharge current, where r _C is the network resistance (usually tenths of an ohm), after which the current decreases quasi-sinusoidally. The maximum possible discharge current can be slightly less than 2U _O / r _C due to the action of inductor 9 at φ ₂ = π or slightly less than U _O / r _C at φ ₂ = π / 2.

запуска тиристора 10, где U_S - напряжение включения динистора 14 (например, для динистора КН102А это напряжение равно 20 В, для динистора КН102Б U_S=28 В, а для динистора КН102Ж U_S=120 В), а также для работы двух цепей удержания тиристоров 5 и 6 в закрытом состоянии при открытом тиристоре 10. Так, опытно установлено, что для включения сильноточного тиристора Т-160 (с импульсным током до 2500 А) достаточно выбирать емкость конденсатора 13, равную 1 мкФ, с использованием динистора с напряжением пробоя в 120 В и понижающего трансформатора 15 с коэффициентом трансформации около 20:1 для всех трех его выходных обмоток. В качестве шунтирующего экстраток в первичной обмотке трансформатора параллельно ей включен диод 16, что исключает отрицательные выбросы в цепи управления тиристора 10 разрядной цепи мостовой схемы. Трансформатор 15 может быть изготовлен на ферритовом кольце К40×25×11 марки М2000НМ или на сердечнике из тонкой трансформаторной стали.Depending on the selected delay time in the integrating RC circuit on the elements 11, 12 and 13, the phase value φ ₂ can easily be set within π / 2 <φ ₂ ≤π by rheostat 12 for a given value of the capacitance of the control capacitor 13, the value of which C _control based on energy requirement

triggering of the thyristor 10, where U _S is the switching voltage of the dinistor 14 (for example, for the KN102A dinistor, this voltage is 20 V, for the KN102B dinistor U _S = 28 V, and for the KN102Z dinistor U _S = 120 V), as well as for the operation of two circuits keeping thyristors 5 and 6 closed when thyristor 10 is open. Thus, it has been experimentally established that to turn on a high-current thyristor T-160 (with a pulsed current up to 2500 A) it is enough to choose a capacitor 13 equal to 1 μF using a dynistor with a breakdown voltage at 120 V and step-down transformer 15 with a coefficient of transformation and about 20: 1 for all three of its output windings. As a shunting extract in the primary winding of the transformer, a diode 16 is connected in parallel with it, which eliminates negative emissions in the control circuit of the thyristor 10 of the discharge circuit of the bridge circuit. The transformer 15 can be made on a ferrite ring K40 × 25 × 11 grade M2000NM or on the core of thin transformer steel.

We assume that the discharge of series-connected storage capacitors with capacitances C will occur according to a quasi-sinusoidal law due to the influence of the inductor 9 at the resonant frequency f _RES = 1 / 2π (LC / 2) ^1/2 , where L is the inductance of the inductor 9. Also, in a first approximation, we assume the loss resistance in the discharge circuit to be negligible (less than the network resistance r _C ). The discharge in this case lasts for a time equal to 1 / 2f _REZ , which is K times less than the charge time T / 4 of the storage capacitors 1 and 2, where T is the period of the network oscillations. Then, according to the law of charge conservation, we can assume that the amplitude of the discharge current is K times higher than the amplitude of the charge current, assuming that the processes of charge and discharge are quasi-sinusoidal when neglecting energy losses inside the discharge circuit, for which copper conductors in the discharge circuit are performed with an increased cross section (see Fig. . one).

Strictly speaking, this ratio of charge and discharge currents is realized when the phase of the alternating voltage of the network is φ ₂ = π, when the instantaneous voltage of the network is zero. In the general case, for π / 2 <φ ₂ <π, the ratio of the amplitudes of the discharge currents and charge K is practically preserved, although when discharging from the voltage 2 U _{O of the} series-connected storage capacitors 1 and 2, the network voltage U ₂ corresponding to the phase φ ₂ is subtracted (see Fig. 2 and 4), and the charge of the capacitor is not completely drained back to the network, and acts on the capacitors residual stress, some minimal voltage U ₂ values at the beginning of discharge with a small discharge time, which consequently reduces the maximum possible magnitude zaryadnog current. Therefore, the claimed technical solution becomes more energy efficient when selecting the phase φ _{2 of} turning on the thyristor 10 of the discharge circuit, equal to φ ₂ = π.

Since the tested induction electric meter takes into account energy as the product of the amount of electricity flowing through its current winding (current at the corresponding time intervals), which are the same when charging and discharging, by the effective voltage in the voltage coil, the ratio L of the energy taken into account by such an electric meter when discharging and charging can be find from expression:

where r _P is the resistance of internal losses in the discharge circuit to the meter. The solution of this equation using the MathCad program with the ratio r _C / (r _C + r _P )] = 0.75, the value K = 30, and the phase φ ₂ = π for T = 20 ms, allows us to find the value L = 1.575.

_Zar charging power W of each of the two storage capacitors of the bridge device is calculated as W _Zar = CU _O ^2/2. At C = 100 μF, we have W _ZAR = 4.5 J., Which determines the average instantaneous charge power over a quarter of the T / 4 period as P _CP = 4W _ZAR / T = 18 // 0.02 = 900 W. Therefore, the average charge current is I _{CP ZAR} = _900/220 = 4.09 A, and the maximum value of the charging current in the phase conductor of the network (with phase φ * = π / 8) is equal to I _{MAX ZAR} = 4 ∗ 1.41 ∗ 4.09 = 23.1 A.

The total charge energy is equal to twice the charge energy of each of the two storage capacitors, that is, equal to 9 J. In this example, therefore, in the half-wave mode of operation of the circuit, the power P _ZAR , which the meter will count when charging, is equal to P _ZAR = 9 J ∗ 50 Hz = 450 Tue In this case, the difference power ΔР in the meter readings will be determined from the expression ΔР = Р _ЗАР (L-1) and will be equal to 0.575 × 450 = 258.7 W. The amplitude of the discharge current will be 693 A (at K = 30) with the total duration of the discharge quasi-sinusoidally similar pulse equal to T // 4K = 0.17 ms - the half-period of the resonance frequency f _RES = 3 kHz. From here we find the inductance value L of the inductor 9, equal to L = 0.028 mH. Such a choke can be made of a thick copper conductor in the form of a multilayer coil without an iron core to prevent its saturation.

The difference power ΔР grows with an increase in the capacitance of the storage capacitors with a corresponding selection of the inductance of the inductor 9 of the bridge circuit.

Consider the features of the control device turning on the thyristor 10 bit circuit. To turn on this thyristor, it is enough to form a trigger pulse with an amplitude of about 5 V and a maximum current of up to 0.5 A (the holding current of the T-160 thyristor is of the order of 0.2 A). This could easily be ensured by an integrating circuit with a control capacitor 13 with a capacity of 1 μF when using a KN102A dinistor with a breakdown voltage of 20 V and with a step-down transformer 15 with a transformation ratio of 3.5: 1, which was experimentally verified. However, when thyristor 10 is turned on, the diagonal of the bridge circuit becomes shorted, and a positive potential with a voltage of U _O ≈300 V is applied to the anodes of the thyristors of charging circuits 5 and 6, which these thyristors tend to turn on, which is unacceptable during the discharge of storage capacitors back into the network. To keep these thyristors in a closed state, pulses of negative polarity are applied to the control electrodes of thyristors 5 and 6 from the additional two secondary windings of transformer 15. These pulses are fed to thyristors 5 and 6 somewhat earlier than the opening of the thyristor 10 of the discharge circuit and recharge the coupling capacitors 21 and 22 through the transition "control electrode-cathode" of the thyristors (having some small resistance for currents in both directions), providing their locked state for the entire duration of the discharge pulse, for which it is necessary to increase the energy of the capacitor 13 by choosing a dynistor with an increased breakdown voltage. After that, the capacitors 21 and 22 are discharged in parallel with the discharge resistors 19 and 20. A slight delay in the inclusion of the thyristor 10 of the discharge circuit relative to the supply of negative pulses to the control electrodes of the thyristors 5 and 6 is achieved by selecting the value of the low resistance resistor 23 in the circuit of the control electrode of the thyristor 10, then there is a regimen selection.

In the control circuits of thyristors 5 and 6 under consideration, zener diodes 17 and 18, anodes connected to the control electrodes of these thyristors are used, which does not interfere with the thyristors being switched on when voltage U _{1 is} reached in the network at phase φ ₁ (see Fig. 2 and 4). The breakdown voltage of these zener diodes is chosen somewhat larger than that which thyristors 5 and 6 are switched on, for example, KS168A zener diodes with a breakdown voltage of 6.8V. These zener diodes for pulses of negative polarity, which occur for a short time to keep thyristors 5 and 6 in the locked state, become ordinary directly connected diodes, which prevails over the action of positive pulses from the anodes of thyristors 5 and 6 on their control electrodes through the inclusion of resistors 7 and 8.

The inventive device is intended for use by developers of newly developed electricity meters. This version of the electric meter was proposed by the author in [7]. For example, it is possible to recommend the development of electric meters working according to a half-wave circuit and allowing current to flow in the measuring multiplier (for example, in the Hall sensor) of the electric meter in only one direction.

Literature

1. Smaller O.F. A device for checking the operation of single-phase induction electric meters, Patent No. 2474825, publ. in No. 4 of 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 electric 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. A device for checking induction electricity meters, Patent No. 2521307, publ. No. 18 dated 06/27/14 (prototype).

6. Smaller O.F. A device for checking induction electric meters, Patent No. 2532861, publ. No. 31 of 11/10/2014.

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, 04/06/2010 US 6362745 B1, 03/26/2002.

EP 1065508 A2, 01/03/2001.

Claims (1)

A device for checking induction electric meters, containing in the branches of the bridge circuit storage capacitors of the same capacitance, the terminals of which are connected on the one hand to the phase and neutral conductors of the network, and on the other hand, to the thyristor of the discharge circuit and a choke installed in the diagonal circuit of the bridge circuit, characterized in that in series with the storage capacitors are included power diodes and thyristors of the charging circuits connected respectively to the neutral and phase conductors with Networks, thyristors of charging circuits are automatically turned on by the resistors connected between the anode and the control electrode of these thyristors and turn off automatically as the storage capacitors charge at the end of the first quarter of the mains voltage periods, the thyristor of the discharge circuit in the diagonal circuit of the bridge circuit turns on after the charge accumulators of the bridge circuit are fully charged in the second quarter of the network voltage periods using a control device consisting of an int connected to the diagonal of the bridge circuit an energizing circuit from a series-connected adjustable limiting resistance and a control capacitor connected to the primary winding of the step-down transformer through a dynistor, the specified primary winding being shunted by the damping diode of the extracurrent, and one of the three secondary windings of this transformer is connected to the junction-electrode-cathode junction of the discharge circuit thyristor bridge circuit through a low-resistance resistor, with the exception of the automatic inclusion of thyristors of the charging circuits when turning on the thyris the torus of the discharge circuit is achieved by means of circuits, including zener diodes connected in series to the control electrode-cathode junctions of the charge circuit thyristors, an additional secondary transformer winding and a coupling capacitor shunted by the discharge resistor.

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