Zero-flux direct current transformer

Abstract

The invention discloses a zero-flux direct current transformer, and belongs to the technical field of transformer application. The invention discloses a zero-flux direct-current current transformer, which comprises a conventional zero-flux direct-current current transformer and a high-speed switching circuit, the high-speed switching circuit is connected in parallel with a secondary loop of the conventional zero-flux direct-current current transformer, and when the output voltage of a power amplifier of the conventional zero-flux direct-current current transformer exceeds the conduction voltage of the high-speed switching circuit, the high-speed switching circuit is short-circuited; and converting the original working mode of the conventional zero-flux direct-current current transformer into the working mode of the current transformer. According to the invention, the original working mode of the conventional zero-flux direct current transformer is converted into the working mode of the current transformer, so that the response capability of the zero-flux transformer to transient large current is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer application, and more specifically, to a zero magnetic flux direct current transformer. Background Art

[0002] When a zero flux transformer is subjected to a transient current exceeding its measurement range, the following situations occur:

[0003] (1) The secondary current cannot track the primary current and the measurement is no longer accurate.

[0004] (2) The core magnetic potential balance condition is destroyed, and the automatic feedback condition of the zero flux transformer is destroyed. Even if the primary current is restored to the normal measurement range, the zero flux transformer may not be able to restore the automatic balance state;

[0005] (3) The primary transient and high current will produce a rapidly changing and large-value magnetic flux in the core, which will in turn induce overvoltage in the secondary winding, which may damage the amplifier and other electronic circuits. Summary of the invention

[0006] In view of the above problems, the present invention proposes a zero-flux DC current transformer, which is characterized by comprising: a conventional zero-flux DC current transformer and a high-speed switching circuit;

[0007] The high-speed switch circuit is connected in parallel with the secondary circuit of the conventional zero-flux DC current transformer;

[0008] When the power amplifier output voltage of the conventional zero flux DC current transformer exceeds the conduction voltage of the high-speed switch circuit, the high-speed switch circuit is short-circuited to convert the original working mode of the conventional zero flux DC current transformer into the current transformer working mode.

[0009] Optionally, it also includes: a voltage monitoring circuit, wherein the input end of the voltage monitoring circuit is connected to the output end of the power amplifier of the conventional zero-flux DC current transformer, and is used to monitor the output voltage of the power amplifier; the output end of the voltage monitoring circuit is connected to the control end of the high-speed switching circuit, and controls the conduction or shutdown of the high-speed switching circuit.

[0010] Optionally, when the voltage monitoring circuit detects that the output voltage of the power amplifier is lower than the maximum unsaturated output voltage U sat When an open circuit signal is sent to the high-speed switch circuit, the high-speed switch circuit adjusts the circuit state to an open circuit state according to the open circuit signal.

[0011] Optionally, when the high-speed switching circuit is in an open circuit state, the conventional zero-flux DC current transformer maintains the original working mode.

[0012] Optionally, when the voltage monitoring circuit detects that the output voltage of the power amplifier is higher than the maximum unsaturated output voltage U sat When a short-circuit signal is sent to the high-speed switch circuit, the high-speed switch circuit adjusts the circuit state to a short-circuit state according to the short-circuit signal.

[0013] Optionally, when the high-speed switching circuit is in a short-circuit state, the conventional zero-flux DC current transformer converts the original working mode into a current transformer working mode.

[0014] Optionally, the voltage monitoring circuit is provided with a threshold voltage, which is slightly lower than the maximum unsaturated output voltage U sat 2V~3V, the output voltage of the power amplifier is monitored based on the threshold voltage.

[0015] Optionally, if the zero-flux DC current transformer includes a voltage monitoring circuit, the high-speed switching circuit includes: a device that can be controlled to be turned on and off, and is used to control the open circuit and short circuit of the high-speed switching circuit.

[0016] Optionally, the high-speed switching circuit includes: a bidirectional uncontrolled switching circuit composed of diodes connected in series and parallel.

[0017] Optionally, the on-state voltage of the bidirectional uncontrolled switch circuit is set to be slightly lower than the maximum unsaturated output voltage U sat 2V~3V, when the output voltage of the power amplifier exceeds the conduction voltage of the high-speed switch circuit, the bidirectional uncontrolled switch circuit is short-circuited, and the zero-flux DC current transformer converts the original working mode to the current transformer working mode.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a zero-flux DC current transformer, comprising: a conventional zero-flux DC current transformer and a high-speed switch circuit; the high-speed switch circuit is connected in parallel with the secondary circuit of the conventional zero-flux DC current transformer; when the output voltage of the power amplifier of the conventional zero-flux DC current transformer exceeds the conduction voltage of the high-speed switch circuit, the high-speed switch circuit is short-circuited, and the original working mode of the conventional zero-flux DC current transformer is converted into a current transformer working mode. The present invention improves the response capability of the zero-flux DC current transformer to transient large currents by converting the original working mode of the conventional zero-flux DC current transformer into a current transformer working mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a conventional zero-flux DC current transformer of the present invention;

[0021] Figure 2 This is the principle diagram of the zero flux DC current transformer of the present invention. DETAILED DESCRIPTION

[0022] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0023] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0024] The general principle of a zero flux transformer is as follows:

[0025] The principle of zero flux DC current transformer (hereinafter referred to as zero flux transformer) is as follows Figure 1 As shown. The toroidal core has two coils, representing the primary winding and the secondary winding respectively. The measured current I1 flows through the primary winding (the number of winding turns is N1), establishing the magnetic potential I1N1. The secondary winding (the number of winding turns is N2) is connected to the output of the power amplifier, and the power amplifier outputs the current I2, which enters the secondary winding and establishes the magnetic potential I2N2. Based on the fluxgate technology (or magnetic modulation technology), the unbalanced magnetic potential in the core will generate a control voltage in the DC detection unit and the AC detection unit. The control voltage changes the output current of the power amplifier so that the magnetic potentials I1N1 and I2N2 are equal in magnitude and opposite in direction, so the core is in a zero flux state. Therefore, the zero flux transformer is an automatic feedback system, and the secondary current automatically tracks the primary current based on the turns ratio.

[0026] The amplifier output current passes through the load and is converted into an output voltage.

[0027] When the zero flux transformer works normally, the primary ampere-turns are equal to the secondary ampere-turns:

[0028] I1N1=I2N2 (1)

[0029] (The principle of the actual zero-flux current transformer is much more complicated, and this part of the content is not involved in this patent. ① There is more than one core; ② The detection principle is not a simple electromagnetic induction.)

[0030] The principle of the present invention is described below: Figure 1 As shown, Figure 1 The output voltage of the medium power amplifier is Uout , the internal resistance of the secondary winding is R2, and the load is U B , according to Ohm's law, the secondary current is:

[0031]

[0032] Therefore, the output current of the zero flux transformer is limited by the following two points of the power amplifier:

[0033] (1) Maximum output voltage limit of the amplifier

[0034] Assume that the amplifier DC supply voltage is +VCC and -VEE (generally VCC = VEE). Due to saturation, the maximum output voltage of the amplifier is generally a few volts lower than the supply voltage (for example, if the amplifier supply voltage is ±24V, its maximum unsaturated output voltage U sat ≈±20V~22V).

[0035] When the primary current I1 of the zero flux transformer increases continuously, due to the aforementioned automatic feedback principle, the secondary current output by the amplifier automatically tracks the primary current, and I2 also increases continuously, and formulas (1) and (2) are established.

[0036] When U out Reach U sat , it cannot increase further, and I2 cannot track I1, so only formula (2) holds.

[0037] Therefore, by increasing the amplifier supply voltages VCC and VEE, the zero flux transformer can measure a wider range of primary currents. However, this introduces a second limitation.

[0038] (2) Internal power consumption limitation of the amplifier

[0039] Limited by the maximum supply voltage that will not damage the amplifier, the supply voltage of the amplifier cannot be increased indefinitely.

[0040] Limited by the maximum non-destructive power consumption, the internal power consumption of the amplifier needs to be controlled within a certain range.

[0041] The voltage drop across the power amplifier is (VCC-U out ), so the internal power consumption of the amplifier is:

[0042] P=(VCC-U out )I2 (3)

[0043] Therefore, in order to improve the measurement range of the zero flux transformer and increase the power supply voltage of the amplifier, the amplifier will suffer very large internal losses, causing the amplifier to burn out.

[0044] The above two factors limit the improvement of the measurement range of zero flux transformers. Generally, the measurement range of zero flux transformers is 1% to 200% of the rated current. Due to different designs, the range may vary, but generally will not exceed 300%.

[0045] Based on this, the present invention proposes a zero flux DC current transformer, such as Figure 2 As shown, it includes: a conventional zero flux DC current transformer and a high-speed switching circuit;

[0046] The high-speed switch circuit is connected in parallel with the secondary circuit of the conventional zero-flux DC current transformer;

[0047] When the power amplifier output voltage of the conventional zero flux DC current transformer exceeds the conduction voltage of the high-speed switch circuit, the high-speed switch circuit is short-circuited to convert the original working mode of the conventional zero flux DC current transformer into the current transformer working mode.

[0048] Among them, it also includes: a voltage monitoring circuit, the input end of the voltage monitoring circuit is connected to the output end of the power amplifier of the conventional zero-flux DC current transformer, which is used to monitor the output voltage of the power amplifier, and the output end of the voltage monitoring circuit is connected to the control end of the high-speed switching circuit to control the conduction or shutdown of the high-speed switching circuit.

[0049] When the voltage monitoring circuit detects that the output voltage of the power amplifier is lower than the maximum unsaturated output voltage U sat When an open circuit signal is sent to the high-speed switch circuit, the high-speed switch circuit adjusts the circuit state to an open circuit state according to the open circuit signal.

[0050] Among them, when the high-speed switching circuit is in an open circuit state, the conventional zero-flux DC current transformer maintains the original working mode.

[0051] When the voltage monitoring circuit detects that the output voltage of the power amplifier is higher than the maximum unsaturated output voltage U sat When a short-circuit signal is sent to the high-speed switch circuit, the high-speed switch circuit adjusts the circuit state to a short-circuit state according to the short-circuit signal.

[0052] Among them, when the high-speed switching circuit is in a short-circuit state, the conventional zero-flux DC current transformer converts the original working mode into the current transformer working mode.

[0053] The voltage monitoring circuit is provided with a threshold voltage, which is slightly lower than the maximum unsaturated output voltage U sat 2V~3V, the output voltage of the power amplifier is monitored based on the threshold voltage.

[0054] Wherein, if the zero-flux DC current transformer includes a voltage monitoring circuit, the high-speed switch circuit includes: a device that can be controlled to be turned on and off, and is used to control the open circuit and short circuit of the high-speed switch circuit.

[0055] Wherein, the high-speed switch circuit includes: a bidirectional uncontrolled switch circuit composed of diodes connected in series and parallel.

[0056] The conduction voltage of the bidirectional uncontrolled switch circuit is set to be slightly lower than the maximum unsaturated output voltage U sat 2V~3V, when the output voltage of the power amplifier exceeds the conduction voltage of the high-speed switch circuit, the bidirectional uncontrolled switch circuit is short-circuited, and the zero-flux DC current transformer converts the original working mode to the current transformer working mode.

[0057] When the primary current of the zero flux transformer is within the normal operating range, the output voltage of the power amplifier is lower than the threshold voltage of the high-speed switching circuit, the high-speed switching circuit is in an open circuit state, and the original zero flux transformer function remains unchanged.

[0058] When the zero flux transformer is subjected to a transient large current that exceeds its normal operating range, the output voltage of the power amplifier reaches or exceeds the threshold voltage of the high-speed switching circuit, the high-speed switching circuit is short-circuited, and the original zero flux transformer is equivalent to a current transformer. Based on the principle of electromagnetic induction, the transient current induced by the secondary winding forms a closed loop through the high-speed switching circuit, the load and the secondary winding. As a result, the zero flux current mutual inductance achieves a correct response to transient large currents and expands the measurement range.

[0059] High-speed switching circuits can be composed of devices that can control on and off, such as thyristors, transistors, and field-effect transistors.

[0060] The voltage monitoring circuit can also be omitted. The high-speed switching circuit is a bidirectional, uncontrolled switching circuit composed of diodes in series and parallel. When the output voltage of the power amplifier exceeds the conduction voltage of the switching circuit, the high-speed switching circuit is short-circuited and the zero flux transformer is converted into a current transformer working mode.

[0061] The effects of the present invention are as follows:

[0062] (1) Improve the response capability of zero flux current transformer to transient large current. When a traditional zero flux current transformer is subjected to a primary current exceeding its operating range, the power amplifier is saturated and the secondary current no longer tracks the primary current. As mentioned above, the present invention can correctly respond to transient primary currents up to 10 times the rated current.

[0063] (2) Improving the stability of the zero-flux transformer automatic balancing system. When a traditional zero-flux transformer is subjected to a transient large current, the primary and secondary currents cannot form a magnetic potential balance due to the saturation of the power amplifier, and the system balance state is easily lost. Even if the primary current is restored to the normal working current range, the zero-flux transformer may not be able to restore the automatic balancing characteristics. When the present invention is subjected to a transient large current, the zero-flux transformer is converted to a current transformer mode, and the core is still in a magnetic potential balance state, thereby improving the stability of the system.

[0064] (3) Avoiding overvoltage in the secondary winding from damaging the zero flux transformer. As mentioned above, when the present invention is subjected to transient large current, the zero flux transformer is converted into the current transformer mode, and the core is still in a magnetic potential balance state. The induced voltage of the secondary winding will not increase to a very large value, thus avoiding damage to the transformer coil or electronic components.

[0065] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0066] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A zero flux DC current transformer, characterized in that: include: Conventional zero flux DC current transformer and high-speed switching circuit; The high-speed switch circuit is connected in parallel with the secondary circuit of the conventional zero-flux DC current transformer; When the power amplifier output voltage of the conventional zero flux DC current transformer exceeds the conduction voltage of the high-speed switch circuit, the high-speed switch circuit is short-circuited to convert the original working mode of the conventional zero flux DC current transformer into the current transformer working mode.

2. The zero flux DC current transformer according to claim 1, characterized in that: Also includes: A voltage monitoring circuit, wherein the input end of the voltage monitoring circuit is connected to the output end of the power amplifier of a conventional zero-flux DC current transformer, and is used to monitor the output voltage of the power amplifier; the output end of the voltage monitoring circuit is connected to the control end of the high-speed switching circuit, and controls the on or off of the high-speed switching circuit.

3. The zero flux DC current transformer according to claim 2, characterized in that: When the voltage monitoring circuit detects that the output voltage of the power amplifier is lower than the maximum unsaturated output voltage U sat When an open circuit signal is sent to the high-speed switch circuit, the high-speed switch circuit adjusts the circuit state to an open circuit state according to the open circuit signal.

4. The zero flux DC current transformer according to claim 3, characterized in that: When the high-speed switch circuit is in an open circuit state, the conventional zero-flux DC current transformer maintains the original working mode.

5. The zero flux DC current transformer according to claim 2, characterized in that: When the voltage monitoring circuit detects that the output voltage of the power amplifier is higher than the maximum unsaturated output voltage U sat When a short-circuit signal is sent to the high-speed switch circuit, the high-speed switch circuit adjusts the circuit state to a short-circuit state according to the short-circuit signal.

6. The zero flux DC current transformer according to claim 5, characterized in that: When the high-speed switch circuit is in a short-circuit state, the conventional zero-flux DC current transformer converts the original working mode into the current transformer working mode.

7. The zero flux DC current transformer according to claim 3, characterized in that: The voltage monitoring circuit is provided with a threshold voltage, which is slightly lower than the maximum unsaturated output voltage U sat 2V~3V, the output voltage of the power amplifier is monitored based on the threshold voltage.

8. The zero flux DC current transformer according to claim 3, characterized in that: If the zero-flux DC current transformer includes a voltage monitoring circuit, the high-speed switch circuit includes: a device that can be controlled to be turned on and off, and is used to control the open circuit and short circuit of the high-speed switch circuit.

9. The zero flux DC current transformer according to claim 1, characterized in that: The high-speed switch circuit comprises: a bidirectional uncontrolled switch circuit formed by connecting diodes in series and parallel.

10. The zero flux DC current transformer according to claim 2, characterized in that: The conduction voltage of the bidirectional uncontrolled switch circuit is set to be slightly lower than the maximum unsaturated output voltage U sat 2V~3V, when the output voltage of the power amplifier exceeds the conduction voltage of the high-speed switch circuit, the bidirectional uncontrolled switch circuit is short-circuited, and the zero-flux DC current transformer converts the original working mode to the current transformer working mode.

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