RU2588581C1 - Power supply with current input - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to electrical engineering, particularly to power supply units with a current input. Novelty is use as input current transformer phase current transformer of a power substation, switching on parallel power key to full-wave rectifier and use of a symmetric thyristor as a switch.

EFFECT: technical result is reduction of overall dimensions.

1 cl, 1 dwg

Description

The invention relates to electrical engineering, in particular to power supplies for microprocessor-based devices for relay protection and automation, and can find application in the implementation of power supplies for organizing power supply of devices from phase currents.

Quite often, switchgears and transformer substations do not have a separate dedicated supply voltage circuit for microprocessor-based relay protection and automation devices. In this case, the power supply of the protection devices is organized from the circuits of current phase transformers, usually for this they use current transformers installed on the phase A bus and phase C bus.

A power supply unit is known, including a current input comprising an input current transformer, the primary winding of which is connected to the secondary winding of a phase current transformer of a transformer station (or switchgear), the secondary one is connected to a push-pull rectifier input, which is loaded through a diode to a capacitive filter and while connected to a parallel-connected power transistor, the power transistor is controlled by a control circuit, the information input of which is connected to a capacitive filter (Block power supply BPK-001, JSC "VNIIR", Cheboksary - http: //www/naladka.by/? id: = 259). This unit is installed on each microprocessor relay protection terminal; it has weight and size characteristics similar to the characteristics of the microprocessor terminal itself.

The Orion-BP-2 device (Zakharov Ο.Γ. Power supplies for circuits with digital relay protection devices, pp. 18-19) is also known. It is a power supply with a current input, the construction structure of which is similar to the BPK-001 power supply. This device, like the above, has large dimensions.

Closest to the proposed technical solution is the well-known power source BPK-4 (O.G. Zakharov, Power Supplies for Circuits with Digital Relay Protection Devices, pp. 14-15), made in accordance with the technical solution of RF patent 2216844. This source contains input current transformer connected to the secondary winding of the phase current transformer mounted on the phase bus, and which is an element of the electrical equipment of the transformer substation; a half-wave rectifier, the input of which is connected to the secondary winding of the input current transformer; a power transistor switch connected by its power terminals parallel to the output of a half-wave rectifier; control circuit, isolation diode and capacitive filter; a dividing diode, the anode connected to the positive output of a half-wave rectifier, the cathode with a capacitor of a capacitive filter; in which, in addition, the information input of the control circuit is connected to the capacitor of the capacitive filter, and the control output is connected to the control electrode of the power transistor.

The principle of operation of the known BPK-4 power supply unit is as follows. Assume that in the initial state the capacitor of the capacitive filter is discharged and there is no voltage on it. In this case, the control circuit does not provide a control voltage to the power transistor and the transistor is closed, i.e. no current flows through its power terminals. When current flows in the phase bus, the current transformer installed on it generates a current in its secondary winding, which enters the primary winding of the input current transformer of the device in question. A capacitor charge current flows through a half-wave rectifier, an isolation diode, and the capacitor plate of a capacitive filter, and the voltage across it, accordingly, begins to increase. At some point in time, the voltage across the capacitor reaches the response level of the control circuit, which provides a control signal to the control electrode of the power transistor, turning it into an open state, i.e. in a state in which current flows through the power terminals of the transistor, and the output of the half-wave rectifier is shunted by the power transistor. This leads to the fact that the flow of the charging current of the capacitor stops, the voltage on it ceases to increase and after a while begins to decrease due to the self-discharge currents of the capacitor and the load current connected in parallel to the capacitor of the capacitive filter. A capacitor discharge with a closed power transistor is prevented by an isolation diode.

After some time, the voltage across the capacitor of the capacitive filter will decrease so much that the control circuit will work again and close the power transistor, thereby restoring the charge circuit of the capacitor of the capacitive filter. The voltage across the capacitor of the capacitive filter will begin to increase again, and the described process of limiting the voltage across the capacitor will be repeated again.

This known power source also has the drawbacks of the technical solutions discussed above - the use of input current transformers leads to an increase in size, such power supplies are often designed to service several microprocessor-based relay protection and automation devices, which in some cases is unacceptable both for economic reasons and for placement conditions and reliability. Providing individual power from the current circuits of substations of each microprocessor device increases the reliability of protection of power distribution equipment, however, the solution of this problem by known technical solutions is associated with increased costs.

The task of the invention is to reduce the cost and reduce the size.

The task is achieved in that a phase current transformer of a transformer substation is used as an input current transformer, while the power switch is connected parallel to the input of a half-wave rectifier, and a symmetric thyristor is used as a power switch, while the control circuit is made in the form of a circuit of series-connected current-limiting resistor and a threshold element, for example, a symmetrical zener diode or a symmetric suppressor, connected at one end to the input of a half-half a period rectifier, the other with a thyristor control electrode.

In FIG. 1 shows a functional diagram of the claimed power supply.

The proposed unit contains (Fig. 1) a power switch 1, which is used as a symmetric thyristor; control circuit 2 in the form of a chain of series-connected current-limiting resistor 3 and a symmetrical zener diode (or a symmetric suppressor) 4; half-wave rectifier 5; capacitive filter 6; Isolation diode 7, connected in the forward direction between the positive terminal of the rectifier and the positive terminal of the capacitive filter 6. The power switch 1 is connected by the power terminals parallel to the input of the half-wave rectifier 5. Parallel to the power terminals of the power switch 1 is a circuit made of series-connected current-limiting resistor 3 and a symmetrical zener diode (or suppressor) 4, the second end of which is connected to the control electrode of the symmetric thyristor of the power switch 1. The findings of the power switch 1 are in Odom proposed power supply terminals of the capacitive filter 6 - power supply output. For galvanic isolation with a load, known DC-to-DC converters based on small-sized pulse transformers (not shown conditionally) can be used.

As a symmetric thyristor 1 can be used commercially available simistor type TC132-80-10 Zaporizhzhya plant "Converter". As a half-wave rectifier 5, a monolithic diode assembly commercially available, for example, KBU10M from CrownpoTechnology; as a capacitive filter 6 can be applied, for example, a commercially available electrolytic capacitor type TKR101M2GL35M from Jamicon; as a dividing diode 7, a Vishay type BYV26E semiconductor diode can be used, the anode of which is connected to the positive terminal of the half-wave rectifier 4, and the cathode is connected to the positive terminal of the electrolytic capacitor of the capacitive filter 6; as the rest of the elements can be used commercially available elements for their intended purpose.

The proposed power supply operates as follows.

Suppose that the input of the device is connected to the secondary winding of a phase current transformer and that there is no current in it. Then, in the initial state, no currents flow in the device and there are no voltages at the terminals of the components. In this case, the charging current of the capacitor of the capacitive filter 6 is absent, the voltage on the filter capacitor is almost zero, the control circuit 2 does not pass current to the control electrode of the simistor 1, it is in the closed state, i.e. no current flows through it. The voltage at the output of the device is zero.

Let a current appear at a certain moment in the secondary winding of the phase current transformer. Since the power switch 1 of the symmetric thyristor is closed, this current will pass through a half-wave rectifier 5, an isolation diode 7 into the capacitor of the capacitive filter 6, the voltage at which will begin to increase. At the same time, the voltage on the power electrodes of the key 1 and in the control circuit 2 will begin to increase. At some point in time, the voltage on the control circuit 2 will reach the breakdown level of the symmetrical zener diode (or symmetric suppressor), as a result of which the control current will flow to the control electrode of the symmetric thyristor 1 and it will go into the open state, the voltage at its terminals will drop to a small level (from 2.2 to 2.5 V depending on the type of thyristor), the symmetrical zener diode (symmetric suppressor) will stop skipping s current in the control circuit 2. The charging current of the capacitive filter 6 is interrupted. The isolation diode 7 prevents the discharge of the capacitive filter 6 through the charge circuit. When changing the polarity of the current phase current transformer, the described processes for the formation of the charging current of the capacitive filter 6 will be repeated again.

Thus, a continuous flow of current of the phase transformer external to the proposed device is carried out with its periodic switching to the charge circuit of the capacitive filter 6, the voltage at which will be maintained and its value will be determined by the breakdown voltage of the symmetrical zener diode (symmetric suppressor).

Information sources

1.http: //www/naladka.by/? Id = 259

2. Zakharov O.G. Power supplies for circuits with digital relay protection devices. - M .: NPF Energoprogress, 2011. - P. 14-15.

3. Patent RU 2216844, H02M 7/12. Combined power source / Yezersky S.V., Mirov A.V., Potapenko V.I., Alekseev Yu.A. - Published: 11/20/2003. Bull. Number 32.

Claims (1)

A power supply unit with a current input, comprising an input current transformer, a half-wave rectifier loaded through a diode diode onto a capacitive filter, a power switch connected in parallel with the half-wave rectifier, and a control circuit, characterized in that a phase current transformer of a transformer substation is used as an input current transformer, the power switch is connected parallel to the input of a half-wave rectifier, a symmetric thyristor is used as the power switch, and the circuit is controlled It is made in the form of a chain of series-connected current-limiting resistor and a threshold element, for example, a symmetrical zener diode or a symmetric suppressor connected at one end to the input of a half-wave rectifier, and the other to the thyristor control electrode.

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