CN108519508A - A Comparator for Measuring AC and DC Current - Google Patents

Abstract

The invention discloses a kind of comparators measuring exchange and DC current.The comparator includes sensing head, modulation transformer, DC side measuring resistance, exchange side measuring resistance, bandpass filter, synchronous demodulator, amplidyne, alternating voltage amplifier and AC power amplifier, measurement head includes identical three units of structure, and each unit includes annular detection iron core, detection winding, electrostatic screen layer, magnetic screen iron core and secondary winding；Unit first and second, modulation transformer, bandpass filter, synchronous demodulator, dc power amplification and DC side measuring resistance constitute the DC detecting system based on double-iron core magnetic modulator principle；Third unit, exchange side measuring resistance, alternating voltage amplifier and AC power amplifier are constituted exchanges detecting system based on single iron core, the present invention can not only measure direct current or measure alternating current, also can measure the DC component and AC compounent of the mixed type electric current of DC stacked exchange.

Description

A Comparator for Measuring AC and DC Current

technical field

The invention belongs to current measuring equipment in the electrical technology, in particular to a comparator for measuring alternating current and direct current.

Background technique

Patent No. ZL92103969.7 titled "An AC-DC Current Comparator", it winds the AC detection winding W _D outside the AC main iron core T ₂ in the measuring head, and then winds the monitoring winding W _K outside the winding , wind the AC zero-adjusting winding W _a outside W _K ; wind the excitation winding W _e outside the two DC main cores _T3 respectively; then assemble the above-mentioned AC and DC winding cores, and wind an electrostatic shield E outside them , and place it in the magnetic shielding iron core _T1 , and wind the AC and DC secondary winding _WS outside _T1 ; the device can measure both DC and AC, and can also measure AC and DC currents at the same time. However, there are the following defects: an AC zero-adjusting winding W _a is set on the AC main iron core _T2 , which is connected in series with the parallel branch of the potential source e and the resistor R and capacitor C, in order to suppress the impact on the AC system due to the ripple of the DC system zero impact. The reason for this effect is that the AC system and the DC system share a set of AC-DC secondary winding _WS and coupling iron core T ₁ , and its influence is unavoidable; in addition, the ripple of the DC system is related to the measured object and the environment, etc. It may be constant, but the potential source e, resistor R and capacitor C connected to the zero-adjusting winding cannot track the ripple change of the DC system, and its industrial application is limited. This is the problem solved by the present invention.

Contents of the invention

In view of the above-mentioned defects of the prior art, the present invention provides a comparator for measuring AC and DC currents, which solves the technical problem of interference between the DC and AC systems existing in the existing comparator device.

In order to achieve the above object, the comparator for measuring AC and DC current proposed by the present invention includes:

Sensor head, modulating transformer, DC side standard resistor, AC side standard resistor, bandpass filter, synchronous demodulator, DC power amplifier, AC voltage amplifier, AC power amplifier;

The sensor head includes a first annular detection core, a first detection winding wound around the first annular detection core, a first electrostatic shielding layer surrounding the first detection winding, and a first magnetic shield placed outside the first electrostatic shielding layer. An iron core and a first secondary winding wound around the first magnetically shielded iron core;

The sensing head also includes a second annular detection iron core, a second detection winding wound around the second annular detection iron core, a second electrostatic shielding layer surrounding the second detection winding, and a second magnetic shield placed outside the second electrostatic shielding layer. a shielding iron core and a second secondary winding wound around the second magnetic shielding iron core;

The sensing head also includes a third annular detection iron core, a third detection winding wound around the third annular detection iron core, a third electrostatic shielding layer surrounding the third detection winding, and a third magnetic shield placed outside the third electrostatic shielding layer. a shielding iron core and a third secondary winding wound around the third magnetic shielding iron core;

The end of the same name of the first secondary winding is connected to the standard resistance of the DC side and grounded, the end of the same name of the first secondary winding is connected to the end of the same name of the second secondary winding; the end of the same name of the first detection winding is connected to the same name of the secondary winding of the modulation transformer The opposite end of the first detection winding is connected to the opposite end of the second detection winding and grounded, the same end of the second detection winding is connected to the opposite end of the secondary winding of the modulation transformer, and the center tap of the secondary winding of the modulation transformer is connected to the The input end of the pass filter, the output end of the band-pass filter is connected to the input end of the synchronous demodulator, the output end of the synchronous demodulator is connected to the input end of the DC power amplifier, and the output end of the DC power amplifier is connected to the second The opposite end of the winding; the opposite end of the third detection winding is connected to the ground, the same end of the third detection winding is connected to the input end of the AC voltage amplifier, the output end of the AC voltage amplifier is connected to the input end of the AC power amplifier, and the AC power amplifier The output end of the second winding is connected to the opposite end of the third secondary winding and grounded, and the same end of the third secondary winding is connected to the standard resistance of the AC side and then grounded.

Preferably, all electrostatic shielding layers are made of copper foil.

Preferably, all the magnetic shielding iron cores have the same shape, and are assembled by winding cold-rolled silicon steel strips into rings and annealing them.

Preferably, all the annular detection iron cores have the same shape, and are obtained by winding a cold-rolled silicon steel strip into a ring shape and annealing.

Preferably, the number of turns of the first detection winding, the number of turns of the second detection winding and the number of turns of the third detection winding are the same.

Preferably, the number of turns of the first secondary winding, the number of turns of the second secondary winding and the number of turns of the third secondary winding are the same.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The present invention rationally arranges the sensing head as three identical independent units, and each unit is composed of an annular detection iron core, a detection winding, an electrostatic shielding layer, an annular magnetic shielding iron core and a secondary winding; the first The unit and the second unit form a DC detection system based on the principle of a dual-core magnetic modulator. The system takes the magnetic modulation detection signal from the center tap of the secondary winding of the modulation transformer, passes through a band-pass filter, a synchronous demodulator, and a DC power The amplifier outputs a DC current to the first and second secondary windings connected in series in the first and second units, and the DC current flows through the standard resistance on the DC side to obtain the measured voltage signal of the DC current; the third unit is composed of a single iron The AC detection system of the core, the system takes the AC detection signal from the end of the same name of the third detection winding, and outputs the AC current to the third secondary winding in the third unit through the AC voltage amplifier and AC power amplifier, and the AC current flows Through the standard resistance of the AC side, the measured voltage signal of the AC current is obtained; this completely breaks through the existing technology that the AC system and the DC system share a set of AC and DC secondary windings and coupling cores, and solves the ripple of the DC system from the source The problem of the influence on the zero point of the AC system eliminates the setting of the AC zero-adjusting winding, potential source, resistor and capacitor parallel branch, making the device debugging and operation more convenient and reliable.

(2) The present invention can not only measure DC current, but also measure AC current, and can also measure the DC component and AC component of the hybrid current in which DC is superimposed on AC.

(3) In the present invention, the sensor head is arranged as three identical independent units, which has superior structure and performance, and the performance and price ratio of the whole machine is higher.

Description of drawings

Fig. 1 is the outline figure of the sensing head in the comparator for measuring alternating current and direct current provided by the present invention;

Fig. 2 is a cross-sectional view of the sensing head in the comparator for measuring AC and DC current provided by the present invention;

Fig. 3 is a circuit diagram of a comparator for measuring AC and DC currents in the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

FIG. 1 is an external view of a sensor head of a comparator for measuring AC and DC currents provided by the present invention, and its section is shown in FIG. 2 . The entire measuring head is in the shape of a ring, and the measuring head T includes a first annular detection core C ₁₂ , a second annular detection core C ₂₂ , a third annular detection core C ₃₂ , a first detection winding W ₁₁ , a second detection winding W ₂₁ , the third detection winding W ₃₁ , the first electrostatic shielding layer E ₁ , the second electrostatic shielding layer E ₂ , the third electrostatic shielding layer E ₃ , the first annular magnetic shielding core C ₁₁ , the second annular magnetic shielding iron core C ₂₁ , the third annular magnetic shield core C ₃₁ , the first secondary winding W ₁₂ , the second secondary winding W ₂₂ and the third secondary winding W ₃₂ ; the first shape detection core C ₁₂ , the second The two-shaped detection core C ₂₂ and the third annular detection core C ₃₂ have the same shape, and the first annular detection core C ₁₂ , the second annular detection core C ₂₂ and the third annular detection core C ₃₂ are respectively wound with turns The first detection winding W ₁₁ , the second detection winding W ₂₁ and the third detection winding W ₃₁ have the same number, and the first detection winding W ₁₁ , the second detection winding W ₂₁ and the third detection winding W ₃₁ are covered with the first Behind the electrostatic shielding layer E ₁ , the second electrostatic shielding layer E ₂ and the second electrostatic shielding layer E ₃ , respectively place the first magnetic shielding core C ₁₁ and the second In the cavities of the second magnetic shielding iron core C ₂₁ and the third magnetic shielding iron core C ₃₁ , outside the first magnetic shielding iron core C ₁₁ , the second magnetic shielding iron core C ₂₁ and the third magnetic shielding iron core C ₃₁ respectively The first secondary winding W ₁₂ , the second secondary winding W ₂₂ and the third secondary winding W ₃₂ are wound with the same number of turns.

Figure 3 shows a circuit diagram of a comparator for measuring AC and DC currents. The primary winding W ₁ shown in Figure 3 is the busbar that transmits the measured AC and DC current I ₁ , passing through the central hole of the sensor head as shown in Figure 1 . The comparator includes a sensing head T, a modulating transformer T ₁ , a DC side standard resistor R _SD , an AC side standard resistor R _SA , a bandpass filter 1, a synchronous demodulator 2, a DC power amplifier 3, an AC voltage amplifier 4, AC power amplifier 5.

The terminal with the same name of the first secondary winding W ₁₂ in the sensor head T is connected to the standard resistor R _SD on the DC side and grounded, and the terminal with the same name of the first secondary winding W ₁₂ is connected to the terminal with the same name of the second secondary winding W ₂₂ ; the first The same-named end of the detection winding W ₁₁ is connected to the same-named end of the secondary winding of the modulation transformer _T1 , the opposite-named end of the first detection winding W ₁₁ is connected to the opposite-named end of the second detection winding W ₂₁ and grounded, and the second detection winding W ₂₁ is grounded. The end with the same name is connected to the end with the same name of the secondary winding of the modulation transformer _T1 , the center tap of the secondary winding of the modulation transformer _T1 is connected to the input end of the band-pass filter 1, and the output end of the band-pass filter 1 is connected to the synchronous demodulator 2 The input terminal and the output terminal of the synchronous demodulator 2 are connected to the input terminal of the DC power amplifier 3, and the output terminal of the DC power amplifier 3 is connected to the opposite terminal of the second secondary winding W ₂₂ .

The opposite end of the third detection winding W ₃₁ is connected to the ground, the same end of the third detection winding W ₃₁ is connected to the input end of the AC voltage amplifier 4, the output end of the AC voltage amplifier 4 is connected to the input end of the AC power amplifier 5, and the AC power The output end of the amplifier 5 is connected to the opposite end of the third secondary winding W ₃₂ , and the same end of the third secondary winding W ₃₂ is connected to the AC side standard resistor R _SA and grounded.

After _the device is put _{into operation ,} the dual _- core magnetic The DC current detection system based on the modulator principle takes the modulation signal of the DC current from the center tap of the secondary winding of the modulation transformer _T1 , passes through the band-pass filter 1, the synchronous demodulator 2, and the DC power amplifier 3 to output the secondary DC current I _2D connects the first secondary winding W ₁₂ and the second secondary winding W ₂₂ in series to realize the magnetic potential balance between the primary DC current I _1D and the secondary DC ampere-turn, that is, I _1D W ₁ =I _2D (W ₁₂ + W ₂₂ ), the secondary direct current I _2D flows through the direct current measurement standard resistance R _SD , and the measured voltage signal I _2D R _SD of the direct current is obtained;

The AC current detection system composed of the third detection winding W ₃₁ and the third annular detection iron core C ₃₂ takes the AC detection signal of the AC current from the end of the same name of the third detection winding W ₃₁ and passes it through the AC voltage amplifier 4, AC power The amplifier 5 outputs the secondary AC current I _2A to the third secondary winding W ₃₂ to realize the magnetic potential balance between the primary AC current I _1A and the secondary AC ampere-turn, that is, I _1A W ₁ =I _2A W ₃₂ , and the secondary AC The current I _2A flows through the AC side standard resistance R _SA to obtain the measured voltage signal I _2A R _SA of the AC current.

The invention breaks through the prior art that the AC system and the DC system share a set of AC-DC secondary windings and coupling iron cores, solves the problem of the influence of the ripple of the DC system on the zero point of the AC system from the source, and eliminates the AC zeroing winding, The setting of the potential source, resistance and capacitance parallel branch makes the debugging and operation of the device more convenient and reliable. The invention can not only measure DC current but also AC current, and can also measure DC component and AC component of hybrid current in which DC is superimposed on AC. Its structure and performance are superior, and the whole machine is cost-effective.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (6)

1. A comparator for measuring AC and DC currents, characterized in that it comprises: a sensor head (T), a modulating transformer (T ₁ ), a DC side standard resistance ( _RSD ), and an AC side standard resistance (R _SA ) , bandpass filter (1), synchronous demodulator (2), DC power amplifier (3), AC voltage amplifier (4), AC power amplifier (5); The sensing head includes a first annular detection core (C ₁₂ ), a first detection winding (W ₁₁ ) wound outside the first annular detection core (C ₁₂ ), surrounding the first detection winding ( W ₁₁ ), the first electrostatic shielding layer (E ₁ ), the first magnetic shielding iron core (C 11 ) placed outside the first electrostatic shielding layer (E ₁ ), and the first magnetic shielding iron core (C ₁₁ ) wound around the first magnetic shielding iron core (C ₁₁ ) outside the first secondary winding (W ₁₂ ); The sensor head also includes a second annular detection core (C ₂₂ ), a second detection winding (W ₂₁ ) wound outside the second annular detection core (C 22 ), and a second detection winding (W ₂₁ ) surrounding the second detection winding. (W ₂₁ ), the second electrostatic shielding layer (E ₂ ), the second magnetic shielding iron core (C 21 ) placed outside the second electrostatic shielding layer (E ₂ ), and the second magnetic shielding iron core (C ₂₁ ) wound around the second magnetic shielding iron core ( C ₂₁ ) outside the second secondary winding (W ₂₂ ); The sensing head also includes a third annular detection core (C ₃₂ ), a third detection winding (W ₃₁ ) wound outside the third annular detection core (C ₃₂ ), and a third detection winding (W ₃₁ ) of the third electrostatic shielding layer (E ₃ ), the third magnetic shielding iron core (C 31 ) placed outside the third electrostatic shielding layer (E ₃ ), and the third magnetic shielding iron core (C ₃₁ ) wound around the third magnetic shielding iron core ( The third secondary winding (W ₃₂ ) outside C ₃₁ ); The terminal with the same name of the first secondary winding (W ₁₂ ) is connected to the DC side standard resistor ( _RSD ) and grounded, and the terminal with the same name of the first secondary winding (W ₁₂ ) is connected to the terminal of the second secondary winding (W ₂₂ ). The end with the same name; the end with the same name of the first detection winding (W ₁₁ ) is connected to the end with the same name of the secondary winding of the modulation transformer (T ₁ ), and the end with the same name of the first detection winding (W ₁₁ ) is connected to the end of the second detection winding (W ₂₁ ). The opposite end is grounded, the same end of the second detection winding (W ₂₁ ) is connected to the opposite end of the secondary winding of the modulation transformer (T ₁ ), and the center tap of the secondary winding of the modulation transformer (T ₁ ) is connected to the bandpass filter ( 1), the output end of the bandpass filter (1) is connected to the input end of the synchronous demodulator (2), and the output end of the synchronous demodulator (2) is connected to the input end of the DC power amplifier (3), The output terminal of the DC power amplifier (3) is connected to the opposite end of the second secondary winding (W ₂₂ ); the opposite end of the third detection winding (W ₃₁ ) is connected to the ground, and the same end of the third detection winding (W ₃₁ ) The terminal is connected to the input terminal of the AC voltage amplifier (4), the output terminal of the AC voltage amplifier (4) is connected to the input terminal of the AC power amplifier (5), and the output terminal of the AC power amplifier (5) is connected to the third secondary winding (W ₃₂ ), the same-named end of the third secondary winding (W ₃₂ ) is connected to the AC side standard resistor (R _SA ) and grounded. 2. The comparator according to claim 1, wherein the material of all the electrostatic shielding layers is copper foil. 3. The comparator according to claim 1 or 2, wherein all the magnetic shielding iron cores have the same shape and are assembled from cold-rolled silicon steel strips wound into rings and annealed. 4. The comparator according to claim 1 or 2, characterized in that, all the annular detection iron cores have the same shape and are obtained by winding a cold-rolled silicon steel strip into a ring and annealing. 5. The comparator according to claim 1 or 2, wherein the number of turns of the first detection winding, the number of turns of the second detection winding and the number of turns of the third detection winding are the same. 6. The comparator according to claim 1 or 2, wherein the number of turns of the first secondary winding, the number of turns of the second secondary winding and the number of turns of the third secondary winding same.