RU2153762C1 - Method of formation of high-power current pulses in low- resistance load and device for its implementation - Google Patents

Abstract

FIELD: power electronics, equipment testing automatic switches. SUBSTANCE: after transit of voltage of supplying network through zero capacitor charged to voltage selected from ratio determined by relation of number of turns to which capacitor is connected to number of all turns of primary winding multiplied by amplitude value of voltage of supplying network is connected simultaneously with connection of supplying network to turns of primary winding of transformer in agreement with method of formation of high-power current pulses in low-resistance load. Device for formation of high-power current pulses in low-resistance load incorporates transformer with load in secondary winding, two bi-directional keys, variable voltage source, control unit, capacitor and charger. EFFECT: reduced amplitude of pulses of current taken from supplying network. 2 cl, 8 dwg

Description

 The invention relates to power electronics and can be used in circuit breaker testing devices.

 A known method of generating powerful current pulses, involving the use of a transformer with a load in the secondary winding. The method consists in the fact that the primary winding of the transformer is connected to the AC mains at an arbitrary time, that is, without synchronization with the voltage of the mains [1].

 However, the known method is characterized by the consumption of high current from the mains.

 Closest to the proposed in its technical essence is a method involving the use of a transformer with a load in the secondary winding, characterized in that the primary winding of the transformer is connected to the mains after a specified period of time after the voltage of the mains passes through zero, that is, synchronized with voltage network [2, 3].

 However, the known method is characterized by the consumption of large amplitude current pulses from the network.

 A device for generating powerful current pulses containing a transformer with a load in the secondary winding, a bi-directional switch and an AC voltage source [1]. The load current pulses are formed when the bidirectional switch is closed, and the switch closes at an arbitrary time, that is, without synchronization with the voltage of the AC voltage source.

 However, the known device is characterized by consumption from an AC voltage source of large current.

 Closest to the proposed in its technical essence is a device containing a transformer with a load in the secondary winding, a bi-directional controlled key, a control device and an AC voltage source. The load current pulses are generated when the bidirectional switch is turned on by the control device, and the switch is turned on after a specified period of time after the voltage of the AC voltage source passes through zero, that is, synchronized with the voltage of the AC voltage source [2, 3].

 However, the known device is characterized by consumption from an AC voltage source of large current.

 The objective of the invention is to reduce the amplitude of the current pulses consumed from the supply network (AC voltage source).

 The method is implemented by a device for generating powerful current pulses in a low-resistance load, comprising a transformer with a load in the secondary winding, a bi-directional controlled key, an alternating voltage source, a control device, a charging device, a capacitor and a second bi-directional controlled key, the capacitor being connected through a second bi-directional controlled key to a part or to all turns of the primary winding of the transformer, and through the charging device to the source of alternating voltage.

 In FIG. 1 is a structural diagram of a device that contains a transformer 1, to the secondary winding of which a load 2 is connected, the first bi-directional controlled switch 3, the first terminal of which is connected to the first pole of the AC voltage source 4, and the second terminal is connected to the first or second terminal of the primary winding of transformer 1 , a capacitor 5, the first terminal of which is connected to the second pole of the AC voltage source 4 and to the third terminal of the primary winding of the transformer 1, the second bi-directional controlled switch 6, first the first terminal of which is connected to the second terminal of the capacitor 5, and the second terminal is connected to the first or second terminal of the primary winding of the transformer 1, the charge device 7, the input of which is connected to the first pole of the AC voltage source 4, and the output is connected to the second terminal of the capacitor 5, control device 8, the inputs of which are connected to the poles of the AC voltage source 4, the first output is connected to the first managed key 3, and the second output is connected to the second managed key 6.

где U_{п.сети m} - амплитудное значение напряжения источника переменного напряжения (питающей сети);
W_1с - количество витков первичной обмотки трансформатора, к которым подключается конденсатор;
W_{1п. сети} - количество витков первичной обмотки трансформатора, к которым подключается источник переменного напряжения (питающая сеть).A device for generating powerful current pulses in a low-impedance load operates as follows. The charge device 7 pre-charges the capacitor 5 to a voltage U _s , determined by the formula

where U _{p. network m} - the amplitude value of the voltage of the source of alternating voltage (mains);
W _1s - the number of turns of the primary winding of the transformer to which the capacitor is connected;
W _{1p. network} - the number of turns of the primary winding of the transformer to which an AC voltage source (mains) is connected.

 After that, when the voltage of the alternating voltage source reaches the amplitude value corresponding to the minimum voltage on the charge device 7, the control device 8 simultaneously turns on the bi-directional controlled keys 3 and 6. The current of the capacitor 5 compensates the reactive component of the current of the primary winding of the transformer 1, and therefore the current consumed from AC voltage source 4 and flowing through a bi-directional controlled switch 3, is significantly less than the current that would be consumed from the source no alternating voltage in the absence of a capacitor 5, a second bidirectional managed key 6 and a charge device 7.

In FIG. Figure 2 shows the timing diagrams corresponding to the formation of pulses in the load for the case when W _1s = W _{1p. network} (and therefore U _c = U _p . _{network m} ). In this case, the second terminal of the first bidirectional managed key 3 and the second terminal of the second bidirectional managed key 6 are connected to the first terminal of the primary winding of the transformer. The following notation is used:
U _{p. Network} - voltage source of alternating voltage (mains):
U _{p. Network m} - the amplitude value of the voltage of the supply network;
U _with - voltage across the capacitor;
i _{p. network} - the current consumed from the supply network;
i _s is the capacitor current;
i _w1 - current of the primary winding of the transformer (2nd output of the primary winding of the transformer is turned off);
i _w2 - current of the secondary winding of the transformer;
t ₁ - time point of connection of a pre-charged capacitor and mains to the primary winding of the transformer; until time t _{1, the} capacitor is charged to the amplitude value of the voltage of the supply network, after this moment the voltage on the capacitor is equal to the voltage of the supply network.

 The essence of the proposed solution lies in the fact that the reactive component of the primary winding current is compensated by the current of the capacitor, and the connection of the pre-charged capacitor and the supply network to the primary winding of the transformer precisely by the proposed method eliminates current surges and ensures the flow of currents at the initial stage of pulse formation, whose amplitudes are not exceed their amplitude values in steady state operation.

 Using the proposed method for generating powerful current pulses for a load having a significant inductive component of the load impedance, as well as for a transformer having a significant dissipation inductance, can significantly reduce the amplitudes of the current pulses consumed from the mains.

The possibility of carrying out the invention is confirmed by the results of mathematical modeling using the Spectrum Software Micro-Cap5 circuit simulation system. Modeling was performed for three variants of the ratio of the number of turns W _1s and W _{1n. network} . In all cases, the mains frequency is 50 Hz; the effective value of the voltage of the mains 220 V (amplitude value 310 V); the cross section of the iron core of the transformer 50 cm ² ; magnetic coupling coefficient of transformer 1; load inductance 2 μH; load resistance 100 μOhm.

 An equivalent load circuit consists of series-connected inductances and active resistances. The indicated parameters correspond to the actual values of the parameters of the circuit breaker testing devices.

The first option corresponds to the relation W _1s = W _{1n. network} (with U _c = U _p . _{network m} ). For mathematical modeling, the circuit shown in FIG. 3. The number of turns of the primary winding W _1s = W _{1p. network} = 440, the number of turns of the secondary winding W ₂ = 8, the capacitance of the capacitor C = 1700 μF. For the capacitor, the initial voltage was set equal to the amplitude value of the supply voltage (310 V). For all variants of circuits that differ in the ratio of the number of turns of the primary winding, the keys K1 and K2 were closed at a time corresponding to the amplitude value of the voltage of the supply network. In FIG. 4 shows the timing diagrams corresponding to the first option, with the previous notation. The letter "m" in the diagrams indicates 10 ^-3 .

The second option corresponds to the relation W _1s = 2W _{1p. network} (with U _c = 2U _p . _{network m} ). For mathematical modeling, the circuit shown in FIG. 5. The number of turns is as follows: W _1s = 880, W _{1p. Networks m} = 440, W ₂ = 8, capacitor capacitance C = 425 μF. For the capacitor, the initial voltage was set equal to 2U _{p.network m} (620 V). In FIG. 6 shows timing diagrams corresponding to the second embodiment, with the previous notation (current i _w1 is indicated in FIG. 5).

The third option corresponds to the ratio of W _1s = 0.5W 1p. _Network (with U _c = 0.5U _p . _{Network m} ). For mathematical modeling, the circuit shown in FIG. 7. The number of turns is as follows: W _1s = 220, W _{1p. mains} = 440, W ₂ = 8, capacitor capacitance = 6800 uF. For the capacitor, the initial voltage was set equal to 0.5 _{U p.network m} (155 V). In FIG. 8 shows timing diagrams corresponding to the third embodiment, with the previous notation (current i _w1 is indicated in FIG. 7).

From the diagrams of FIG. 4, 6, 8 it follows that the use of the proposed method for all three variants of the ratio of the number of turns reduces the amplitude of the current pulses consumed from the mains by one and the same number of times (about 7 times). For all options, when the capacitor is excluded from the circuit, the current consumed from the supply network will be equal to the current i _w1 . But it is necessary to consider the following circumstances. With the exception of the capacitor from the circuit of FIG. 5, the current i _{w1 will} increase by about 2 times while maintaining the same current in the load. With the exception of the capacitor from the circuit of FIG. 7, the current i _w1 will decrease by about 2 times while maintaining the same current in the load.

Literature
1. Musaelyan E.S. Adjustment and testing of electrical equipment of power plants and substations. - M .: Energoatomizdat, 1986, p. 102-104.

 2. Report on the application of methods for the experimental determination of K3 currents in electric networks of a rectified alternating operational current. JSC "Firm ORGRES".

 3. Complete test device "SATURN-M", "SATURN-M1". Technical description, instruction manual, passport. - M .: 1993.

Claims (1)

1. A method of generating powerful current pulses in a low-impedance load, which consists in the fact that after a predetermined period of time after the supply voltage passes through zero, the primary winding of the transformer is connected to the mains, characterized in that at the same time as connecting the mains to the turns of the primary winding of the transformer _1n.seti W in an amount and at a time corresponding to the peak value U _{n.seti m} mains voltage, is connected a capacitor charged to _voltage U, to wrap the same obmo ki in an amount W _1c, the voltage U is selected _with the relation

2. A device for generating powerful current pulses in a low-impedance load, comprising a transformer with a load in the secondary winding, a bi-directional controlled switch, an alternating voltage source and a control device, characterized in that a charge device, a capacitor and a second bi-directional controlled key are introduced into it, the capacitor connected through a second bidirectional controlled key to a part or to all turns of the primary winding of the transformer, and through a charging device to a source of alternating voltage shreds.

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