A new passive AC current acquisition circuit

Abstract

The present invention discloses a novel passive AC current acquisition circuit, comprising first to third low-power coils, first to fourth resistors and a high-precision mutual inductor, wherein the connected ends of the first low-power coil, the second low-power coil and the third low-power coil are grounded and connected to one end of the primary coil of the high-precision mutual inductor; the other end of the first resistor, the other end of the second resistor and the other end of the third resistor are connected, and the connected ends of the first resistor, the second resistor and the third resistor are connected to the other end of the primary coil of the high-precision mutual inductor; the fourth resistor is connected to the secondary coil of the high-precision mutual inductor. The novel passive AC current acquisition circuit of the present invention can acquire three-phase large current signals, convert the large current signals into small voltage signals for output, and synthesize a current zero sequence by hardware and convert it into a voltage signal, thereby ensuring the accuracy of the amplitude and the accuracy of the phase at the same time.

Description

Technical Field

[0001] The invention relates to a novel passive alternating current acquisition circuit. Background Art

[0002] Conventional CT uses electromagnetic coils to output current signals, but has disadvantages such as inability to open the circuit and large size. In addition, conventional CT requires a separate zero-sequence current coil to produce zero sequence, and the accuracy of this coil is difficult to increase. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a novel passive AC current acquisition circuit, which can acquire three-phase large current signals, convert the large current signals into small voltage signals for output, and synthesize a current zero sequence by hardware and convert it into a voltage signal, thereby ensuring the accuracy of the amplitude and the accuracy of the phase.

[0004] The technical solution to achieve the above purpose is: a new passive AC current acquisition circuit, including first to third low-power coils, first to fourth resistors and a high-precision mutual inductor, wherein:

[0005] One end of the first low-power coil, one end of the second low-power coil and one end of the third low-power coil are connected, and the connected ends of the first low-power coil, the second low-power coil and the third low-power coil are grounded and connected to one end of the primary coil of the high-precision mutual inductor;

[0006] The other end of the first low-power coil, the other end of the second low-power coil and the other end of the third low-power coil are connected to one end of the first resistor, one end of the second resistor and one end of the third resistor in a one-to-one correspondence;

[0007] The other end of the first resistor, the other end of the second resistor and the other end of the third resistor are connected, and the connected ends of the first resistor, the second resistor and the third resistor are connected to the other end of the primary coil of the high-precision mutual inductor;

[0008] The fourth resistor is connected to the secondary coil of the high-precision transformer.

[0009] The above-mentioned novel passive AC current acquisition circuit, wherein the first low-power coil and the first resistor are connected in series to acquire the A-phase positive-sequence current signal, and convert the A-phase positive-sequence current signal into a voltage signal for output;

[0010] The second low-power coil is connected in series with the second resistor to collect the positive-sequence current signal of the phase B, and convert the positive-sequence current signal of the phase B into a voltage signal for output;

[0011] The third low-power coil and the third resistor are connected in series to collect the C-phase positive-sequence current signal, and convert the C-phase positive-sequence current signal into a voltage signal for output;

[0012] The secondary coil of the high-precision mutual inductor is connected in parallel with the fourth resistor to collect the zero-sequence current value and convert the zero-sequence current value into a voltage signal for output.

[0013] The novel passive AC current acquisition circuit of the present invention acquires three-phase large current signals, converts the large current signals into small voltage signals for output, and synthesizes a current zero sequence by hardware and converts it into a voltage signal, thereby ensuring the accuracy of the amplitude and the phase at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The circuit diagram of the novel passive AC current acquisition circuit of the present invention is shown in FIG. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the technical solution of the present invention, the specific implementation methods thereof are described in detail below in conjunction with the accompanying drawings:

[0016] See also Figure 1 The best embodiment of the present invention is a novel passive AC current acquisition circuit, comprising first to third low-power coils, first to fourth resistors and a high-precision mutual inductor CT0.

[0017] One end of the first low-power coil CTA, one end of the second low-power coil CTB and one end of the third low-power coil CTC are connected, and the connected ends of the first low-power coil CTA, the second low-power coil CTB and the third low-power coil CTC are grounded and connected to one end of the primary coil of the high-precision transformer CT0; the other end of the first low-power coil CTA, the other end of the second low-power coil CTB and the other end of the third low-power coil CTC are connected to the first resistor R ia One end of the second resistor R ib One end and the third resistor R ic One end of the first resistor R ia The other end of the second resistor R ib The other end and the third resistor R ic The other end of the first resistor R ia , the second resistor R ib and the third resistor R ic The connecting end is connected to the other end of the primary coil of the high-precision transformer CT0; the fourth resistor R I0 Connected to the secondary coil of the high-precision transformer CT0.

[0018] A novel passive alternating current acquisition circuit of the present invention comprises a first low-power coil CTA and a first resistor R ia Connect in series to collect the positive sequence current signal I of phase A A , and the A phase positive sequence current signal I A Converted into voltage signal U Ia Output; the second low power coil CTB and the second resistor R ib Connect in series to collect the positive sequence current signal I of phase B B , and the B phase positive sequence current signal I B Converted into voltage signal U Ib Output; the third low power coil CTC and the third resistor R ic Connect in series to collect the positive sequence current signal I of phase C C , and the C phase positive sequence current signal I C Converted into voltage signal U Ic Output; first resistor R ia , the second resistor R ib and the third resistor R ic The connecting end is connected to the primary coil of the high-precision transformer CTO, the secondary coil of the high-precision transformer CTO is connected in parallel with the fourth resistor RI0, the zero-sequence current value is collected, and the zero-sequence current value is converted into a voltage signal U I0 Output.

[0019] In a novel passive alternating current acquisition circuit of the present invention:

[0020] (1) It uses a low-power coil and converts the current signal into a voltage signal, so there is no open circuit problem and the volume is greatly reduced;

[0021] (2) No separate zero-sequence current coil is required. The zero-sequence current value is collected by hardware synthesis, that is, a high-precision mutual inductor CTO is connected to a resistor, and the zero-sequence current value is converted into a voltage signal output, which saves space and can achieve high accuracy.

[0022] (3) Using voltage signal output, the wiring on the controller side and the cable can use thin wires, which is convenient for wiring.

[0023] In summary, the novel passive AC current acquisition circuit of the present invention can acquire three-phase large current signals, convert the large current signals into small voltage signal outputs, and synthesize a current zero sequence by hardware and convert it into a voltage signal, thereby ensuring the accuracy of the amplitude and the accuracy of the phase.

[0024] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A new passive AC current acquisition circuit, characterized in that: It includes first to third low-power coils, first to fourth resistors and a high-precision mutual inductor, wherein: One end of the first low-power coil, one end of the second low-power coil and one end of the third low-power coil are connected, and the connected ends of the first low-power coil, the second low-power coil and the third low-power coil are grounded and connected to one end of the primary coil of the high-precision mutual inductor; The other end of the first low-power coil, the other end of the second low-power coil and the other end of the third low-power coil are connected to one end of the first resistor, one end of the second resistor and one end of the third resistor in a one-to-one correspondence; The other end of the first resistor, the other end of the second resistor and the other end of the third resistor are connected, and the connected ends of the first resistor, the second resistor and the third resistor are connected to the other end of the primary coil of the high-precision mutual inductor; The fourth resistor is connected to the secondary coil of the high-precision transformer.

2. A novel passive AC current acquisition circuit according to claim 1, characterized in that: The first low-power coil and the first resistor are connected in series to collect the positive-sequence current signal of phase A, and convert the positive-sequence current signal of phase A into a voltage signal for output; The second low-power coil is connected in series with the second resistor to collect the positive-sequence current signal of the phase B, and convert the positive-sequence current signal of the phase B into a voltage signal for output; The third low-power coil and the third resistor are connected in series to collect the C-phase positive-sequence current signal, and convert the C-phase positive-sequence current signal into a voltage signal for output; The secondary coil of the high-precision mutual inductor is connected in parallel with the fourth resistor to collect the zero-sequence current value and convert the zero-sequence current value into a voltage signal for output.

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