CN1168992C - DC Current Sensing Device - Google Patents

Abstract

The present invention relates to a DC current sensing device which belongs to a DC current measurement device in electrotechnology. The present invention has the advantages of the DC current measurement of a commutation system of no oscillation sources, no large power drive, high precision, high stability and high reliability. The device comprises a sensing head, a power transformer, a driver transformer, a resistor, inductance, a diode, an operational amplifier and a driver, wherein the sensing head has the structure that a first annular detecting iron core and a second annular detecting iron core are respectively wound with first detecting winding and second detecting winding the number of turns of which is identical. After the assembly is finished, the outside of the sensing head is wound with compensation winding, and the integration is arranged in a screening iron core cavity the outside of which is wound with secondary winding. The present invention has both the advantages of open loop measurement and closed loop measurement, and has no oscillation brought by high voltage gain. The present invention avoids high-power drive, and has high measuring precision, high stability and strong anti-interference ability. The present invention can be widely used for the DC current online detection of the industry, such as electric smelting, electrochemistry, electroplating, electric power, electric vehicles, etc.

Description

DC Current Sensing Device

technical field

The invention belongs to the direct current measuring equipment in the electrotechnical field.

Background technique

Patent No. ZL 01219393.3 is a utility model patent "high-precision strong DC sensor". There is no magnetic core in the sensor housing, and the detection elements are evenly arranged in pairs along the inner periphery of the housing, and then filled with epoxy resin around the elements, and the detection elements fixed in the housing. The detection element directly detects the magnetic field generated by the bus current, and through the amplification of the circuit, the output signals of multiple detection elements are superimposed so that the output signal matches the data displayed on the test bench. This device has the common advantages of the open-loop principle, that is, there is no oscillation problem caused by the high voltage gain of the closed-loop system, and there is no high-power drive problem caused by maintaining the balance of the magnetic potential; the circuit and structure are simple. The disadvantage is that the accuracy and stability of the measurement are poor. The patent uses a coreless structure in the sensor housing. From a theoretical analysis, it cannot realize the installation of infinitely many detection elements, and it cannot guarantee its measurement reliability; anti-interference ability Poor, especially poor ability to resist external magnetic field interference and temperature changes.

Patent No. ZL 97240789.8 is a utility model patent "DC high current sensor". Its circuit includes a double-coupled magnetic detector to collect signals, and uses feedback technology to achieve magnetic potential balance for measurement. This device belongs to the principle of closed-loop measurement, so it has the common advantages of the closed-loop principle, that is, high measurement accuracy, good stability, and strong anti-interference ability. Disadvantages: (1) Oscillation problems caused by high voltage gain of the closed-loop system and high-power drive problems caused by maintaining magnetic potential balance; (2) Circuit debugging is complicated.

Contents of the invention

The invention provides a magnetic potential self-balancing feedback compensation type direct current sensing device, which can be widely used in rectifying system direct current with a structure of no oscillation source, no high-power drive and high-precision, high-stability and high-reliability operation Measurement.

The DC current sensing device of the present invention comprises a sensing head, a power transformer, an excitation transformer, a resistor, and a diode, and is characterized in that:

(1) The structure of the sensing head is a first annular detection iron core and a second annular detection iron core with the same shape, respectively wound with a first detection winding and a second detection winding with the same number of turns. After assembling, their outer Wound with a compensation winding, the whole is placed in the annular cavity of the shielded iron core, and a secondary winding is wound outside the shielded iron core;

(2) The terminal with the same name of the secondary winding is connected in series with the first inductance coil, the standard resistor and then grounded, the terminal with the same name of the secondary winding is connected with the cathode of the first diode, and the anode of the first diode is connected with the terminal with the same name of the secondary winding of the power transformer , the opposite end of the secondary winding is grounded;

(3) The same-named end of the first detection winding is connected to the different-named end of the second detection winding, and connected to the same-named end of the secondary winding of the excitation transformer, and the same-named end of the secondary winding is connected to the first sampling resistor and the second sampling resistor at the same time One end of the first sampling resistor and the other end of the first sampling resistor are connected to the anode of the second diode and grounded, the cathode of the second diode is connected to the opposite end of the first detection winding, and the other end of the second sampling resistor is connected to the operational amplifier and the input end of the driver and the first The anode of the three diodes, the cathode of the third diode is connected to the end of the same name of the second detection winding;

(4) The output terminal of the operational amplifier and the driver is connected to the opposite end of the compensation winding, and the same end of the compensation winding is connected in series to the second inductance coil and then connected to the connection point between the first inductance coil and the standard resistor.

In the direct current sensing device, the sensing head can be in the shape of a ring composed of two half-rings, the first annular detection core, the second annular detection core, the shielding iron core, the first detection winding, the second The detection winding, the compensation winding and the secondary winding are evenly arranged on the two half-rings, and the windings between the two half-rings are electrically connected by wires.

In the direct current sensing device, the shielding iron core can be wound into a ring shape by strip-shaped cold-rolled silicon steel sheets, and assembled to form a ring shape with a cavity inside.

The invention not only has the advantages of open-loop measurement such as the patent No. ZL 01219393.3 "high-precision strong DC sensor", that is, there is no oscillation problem caused by the high voltage gain of the closed-loop system, and it also avoids the high-power drive caused by maintaining the balance of the magnetic potential Problem: The present invention also has the advantages of closed-loop measurement such as the patent No. ZL97240789.8 "DC large current sensor", that is, high measurement accuracy, good stability, strong anti-interference ability, automatic tracking and compensation characteristics, and the performance and price ratio of the whole machine high. It can be widely used in online detection of DC current in industries such as electrosmelting, electrochemistry, electroplating, electric power, and electric vehicles.

Description of drawings

Fig. 1 is the appearance diagram of the sensing head of the DC current sensing device of the present invention.

Figure 2 Cross-sectional view of the sensor head.

Fig. 3 is a circuit diagram of the DC current sensing device of the present invention.

Detailed ways

The present invention is further described now in conjunction with accompanying drawing.

As shown in Figure 1, the shape of the sensing head of the DC current sensor device is a circular ring composed of two half rings, and its cross-section is shown in Figure 2: the first annular detection core C ₂ and the second annular detection core with the same shape The first detection winding W _D1 and the second detection winding W _D2 with the same number of turns are respectively wound on the iron core C ₃ , and after assembly, a compensation winding W _C is wound on the outside of them, and then they are placed in an annular cavity as a whole In the cavity of the shielded iron core C ₁ of the structure, a secondary winding W ₂ is wound outside the shielded iron core C ₁ . The primary winding W ₁ shown in FIG. 3 is the bus bar for transmitting the measured DC current I ₁ , passing through the central circular hole of the sensing head as shown in FIG. 1 .

Figure 3 shows the circuit diagram of the DC current sensing device. The terminal with the same name of the secondary winding W ₂ in the sensor head T is connected to the first inductance coil L ₁ of the secondary balance current I _2S and the standard resistor R _S in sequence, and then connected to the ground, and the terminal with the same name is connected to the first diode D ₁ The cathode is connected, the anode of the first diode _D1 is connected to the same-named end of the secondary winding of the power transformer _T1 , and the opposite-named end of the secondary winding is connected to the ground point; the same-named end of the first detection winding _WD1 is connected to the second After the opposite end of the detection winding WD ₂ is connected, it is connected to the opposite end of the secondary winding of the excitation transformer T ₂ , and its same end connects two detection signals to one end of the first sampling resistor R ₁ and the second sampling resistor R ₂ connected together; the other end of the resistor _R1 and the anode of the second diode _D2 are connected to the ground at the same time, and the cathode of the diode _D2 is connected to the opposite end of the first detection winding _WD1 ; the other end of the resistor _R2 At the same time, it is connected to the input terminal of the operational amplifier and driver A, and the anode of the third diode _D3 , and the cathode of the third diode _D3 is connected to the same name end of the second detection winding W _D2 ; the operational amplifier and driver A The output end is connected to the opposite end of the compensation winding W _C , and the same end of the compensation winding is connected to one end of the second inductance coil _L2 of the secondary compensation current _I2C , and the other end is connected to the first inductance coil _L1 and the standard resistance R _S on the node connected in series.

After the device is put into operation, the half-wave current provided by the power transformer _T1 through the diode _D1 flows through the secondary winding _W2 , and the secondary balance is automatically established by the shielded iron core _C1 and the secondary winding _W2 within half a cycle The DC magnetic potential balance between the current I _2S and the primary measured current I ₁ , this magnetic potential balance is determined by the characteristics of the approximately rectangular magnetization curve of the iron core, which avoids the use of high-power electronic devices to drive the secondary balance current The active method of I _2S achieves DC magnetic potential balance. It is different from the DC magnetic potential balance composed of high open-loop voltage gain (generally greater than 1000 times), PID adjustment link and high-power driven source drive in the traditional closed-loop system, so there is no system oscillation and high-power drive problems. Because the magnetic potential balance of this kind is generally not as high as the magnetic potential balance of the closed-loop system, the present invention rationally designs the iron core as a central cavity structure, and sets a zero-ampere-turn detection iron core _C2 in the cavity of the shielding iron core _C1 , C ₃ and detection windings W _D1 , W _D2 are used to detect the ampere-turn difference of the above-mentioned DC magnetic potential balance in the half cycle. After being excited by the excitation transformer _T2 , _{the output current} signals _of the detection windings _{WD1 and WD2} are fed back to The compensation winding W _C realizes the DC zero-ampere-turn compensation of the detection cores C ₂ and C ₃ and maintains a high-precision DC magnetic potential balance. In the present invention, most of the magnetic potential W ₁ I ₁ of the primary measured current _I 1 has been automatically balanced by the current magnetic potential W ₂ I _2S provided by the secondary winding W ₂ from the AC power transformer T ₁ , and the residual magnetic potential The compensation current I _2C generated by W ₁ I ₁ -W ₂ I _2S is very small, the power consumption of the operational amplifier and driver A is small, the reliability is high, and the price is also low. More meaningfully, the compensation current feedback system composed of detection cores C ₂ , C ₃ , detection windings W _D1 , W _D2 , compensation winding W _C , and electronic module A is a DC automatic compensation system with low voltage magnification , instead of a closed-loop feedback system formed by high voltage amplification, so there is no oscillation problem caused by the high voltage gain of the closed-loop system. However, the compensation current I _2C of the feedback system still has the characteristics of automatic tracking compensation of the closed-loop system. Although the DC magnetic potential balance and differential current feedback compensation system works in half a cycle, the secondary balance current I _2S and the secondary compensation current I _2C flow through the filter inductance coils L ₁ and L ₂ respectively, namely The desired direct current can be obtained. The secondary balance current I _2S and the secondary compensation current I _2C are superimposed through the standard resistance R _S to obtain the secondary current I ₂ =I _2S +I _2C of the DC current sensing device, thereby realizing the secondary ampere-turn W ₂ I ₂ and The magnetic potential of the primary DC ampere-turn W ₁ I ₁ is almost completely balanced W ₂ I ₂ ≈W ₁ I ₁ , usually the number of turns of the measured DC current bus is 1 turn, that is, W ₁ = 1, the secondary winding W ₂ and the compensation The number of turns of the winding W _C is the same, that is, W ₂ =W _C is multi-turn, so the secondary small current I ₂ =(W ₁ /W ₂ )I ₁ accurately represents the measured primary current, and the ratio coefficient W ₁ /W ₂ is the turns ratio of primary and secondary windings, which is a constant. The secondary current I ₂ flows through the standard resistance R _S , and the voltage value I ₂ R _S is obtained on the standard resistance, so as to meet the requirements of digital instruments, computer sampling, etc. that output voltage signals.

Claims (3)

1. a DC current sensing device comprises sensing head, power transformer, driver transformer, resistance, diode, it is characterized in that:

(1) described sensing head structure is that the first identical annular of shape detects iron core and second annular detects iron core, be wound with the identical first detection winding and second of the number of turn respectively and detect winding, after assembly unit, the first detection winding and second detects the winding outside and is wound with the compensation winding, integral body places the toroidal cavity of shielding iron core, and the shielding iron core outside is wound with Secondary Winding;

(2) end of the same name of Secondary Winding is connected in series ground connection after first telefault, the measuring resistance successively, and Secondary Winding different name termination first diode cathode, first diode anode connect power transformer secondary winding end of the same name, this secondary winding different name end ground connection;

(3) first ends of the same name that detect winding link to each other with the second different name end that detects winding, and be connected with exciter transformer secondary winding different name end, this secondary winding end of the same name connects an end of first sample resistance and second sample resistance simultaneously, first sample resistance another termination second diode anode and ground connection, second diode cathode and first detects winding different name end and is connected, the second sample resistance other end concatenation operation amplification and driver input end and the 3rd diode anode, the 3rd diode cathode connect second and detect winding end of the same name;

(4) computing amplification and driver output end connect compensation winding different name end, compensation winding end of the same name is connected on the tie point of first telefault and measuring resistance after being connected in series second telefault.

2. DC current sensing device as claimed in claim 1, it is characterized in that described sensing head is synthetic circular of two semi-rings, first annular iron core, the second annular detection iron core, shielding iron core, the first detection winding, the second detection winding, compensation winding and the Secondary Winding of detecting evenly arranged on two semi-rings, and each winding is electrically connected by lead between two semi-rings.

3. DC current sensing device as claimed in claim 1 or 2 is characterized in that shielding iron core is wound into ring-type by banded cold-reduced silicon sheet, has the annular of cavity in constituting through assembly unit.

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