Compensating current sensor with magnetic shunt. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Measuring technology

 Comments on the article

The described design of the sensor used in measuring high currents differs from similar devices currently used in the presence of a magnetic shunt, which reduces the power consumption, weight and dimensions of the device.

To measure high currents (of the order of tens of kiloamperes), the classical circuit of a compensation type sensor (Fig. 1), on which industrial products are built [1], is unacceptable.

The principle of operation of such sensors is based on the compensation of the magnetic field created in the magnetic circuit by the measured current by means of the current of the compensation winding. The current transformer TA1 is a closed magnetic circuit with a winding, covering a bus with a measured current, in the gap of which a Hall sensor (U1) is installed. When current passes through the bus, a magnetic flux is created in the magnetic circuit that surrounds it, causing a voltage proportional to the measured current to appear in the Hall sensor. This voltage, amplified by an operational amplifier (DA1) and a power amplifier on transistors VT1, VT2, causes a current in the TA1 winding, which compensates for the magnetic flux in the magnetic circuit.

To compensate for the magnetic field created, for example, by a current of 100 kA, the current through the compensation winding must be equal to 100/n kA, where n is the number of turns of this winding. In this case, the power of the output amplifier and the mass of the sensor may be too large.

To reduce the compensation current in the proposed sensor (Fig. 2), the magnetic flux is compensated not in the entire section of the magnetic circuit 2, but in a limited area with a magnetic resistance less than the resistance of the entire magnetic circuit.

At the installation site of the Hall sensor 3, where the magnetic flux bifurcates (AB), the magnitude of the magnetic induction created by the measured current I in bus 1, B = μμ0I / 2l (at l "d), where μ is the magnetic permeability of the magnetic circuit material; μ0 is the magnetic vacuum permeability.

To compensate for the magnetic flux created by the measured current in this section, the current of the compensation winding 4 I1 = Vx2s1/μμ0 = Ixd/l.

The current of the compensation winding I1 is less than the measured current I by l/d times, which makes it possible to implement a sensor of acceptable weight and dimensions.

In the proposed sensor l=100 mm, d = 1 mm, therefore, with a measured current of 100 kA, the compensation current is created by a current of 1/n kA, where n is the number of turns of the compensation winding.

A compensation sensor with a magnetic shunt of this design has the following characteristics.

• Rated measured current, kA......20
• The maximum measured pulse current with a duration of not more than 10 ms for 1 min, kA ..... 100
• Transformation ratio ...... 1/5000
• Maximum output current at measured current 100 kA, mA......200
• Basic error for the rated current value, no more than, %......1
• Zero bias current, not more than, mA......0,2
• Frequency range, kHz......0...10
• Window dimensions for current bus, mm......40x120
• Cross section of the magnetic circuit, not less than, mm......55
• Dimensions, mm......200x200x100
• Weight, kg ...... no more than 3

The implementation of such a design is possible when using a magnetic circuit with a high saturation induction, for example, GAMMAMET 440C1 with a linear magnetization characteristic up to 1...1,2 T [2, 3].

To reduce the influence of external magnetic fields, it is advisable to use two magnetic circuits and Hall sensors in the design shown in Fig. 3.

Here, the gap l in the magnetic circuit around bus 1 with current is divided into two equal sections between the magnetic circuits 2, 3. The currents of the compensation windings 6 and 7 in this circuit are summed up. If the external magnetic field at the installation site of one of the Hall sensors (4 or 5) coincides in direction with the magnetic field created by the measured current, then at the installation site of the other Hall sensor it is opposite in direction. If the signals of the Hall sensors 4, 5, due to the magnetic field of the measured current, have the same polarity, then the signals from the external magnetic field are pickups of different polarity, and therefore the resulting signal from the external magnetic field is zero.

An amplifier for such a device needs a fairly low-power one - its current consumption is not more than 0,25 A at a supply voltage of +15 V.

If it is impossible to purchase the necessary magnetic circuit, you can use cold-rolled electrical steel grades E310, E320, for which the saturation induction is also quite high, and with a measurement error of about 1%, this material is quite suitable.

Literature

1. Prospectus of the firm "LEM".
2. Prospect NPP "Gamma" (Yekaterinburg).
3. Starodubtsev Yu., Keilin V., Belozerov V. GAMMAMET magnetic cores. - Radio, 1999, No. 6, p. 48-50.

Author: A. Aldokhin, Chernihiv, Ukraine

See other articles Section Measuring technology.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Controlling objects using air currents 04.05.2024

The development of robotics continues to open up new prospects for us in the field of automation and control of various objects. Recently, Finnish scientists presented an innovative approach to controlling humanoid robots using air currents. This method promises to revolutionize the way objects are manipulated and open new horizons in the field of robotics. The idea of ​​controlling objects using air currents is not new, but until recently, implementing such concepts remained a challenge. Finnish researchers have developed an innovative method that allows robots to manipulate objects using special air jets as "air fingers". The air flow control algorithm, developed by a team of specialists, is based on a thorough study of the movement of objects in the air flow. The air jet control system, carried out using special motors, allows you to direct objects without resorting to physical ... >>

Purebred dogs get sick no more often than purebred dogs 03.05.2024

Caring for the health of our pets is an important aspect of the life of every dog ​​owner. However, there is a common assumption that purebred dogs are more susceptible to diseases compared to mixed dogs. New research led by researchers at the Texas School of Veterinary Medicine and Biomedical Sciences brings new perspective to this question. A study conducted by the Dog Aging Project (DAP) of more than 27 companion dogs found that purebred and mixed dogs were generally equally likely to experience various diseases. Although some breeds may be more susceptible to certain diseases, the overall diagnosis rate is virtually the same between both groups. The Dog Aging Project's chief veterinarian, Dr. Keith Creevy, notes that there are several well-known diseases that are more common in certain breeds of dogs, which supports the notion that purebred dogs are more susceptible to disease. ... >>

Random news from the Archive TLV73333P New 300mA Capacitorless LDO Regulator 01.05.2015 Texas Instruments' new low dropout TLV73333P series TLV733P integrated regulator is designed to operate in devices with current consumption up to 300 mA. The TLV73333P provides a fixed output voltage of 3,3V and generally does not require any wiring to operate. Stable operation is ensured even without connecting an input and output capacitor, which can be useful in battery-powered applications where high starting currents must be avoided. Despite the low price, the TLV73333P stabilizer has good parameters - the voltage drop at the maximum current is less than 122 mV, the internal consumption current is 34 μA, there is a control input and an automatic discharge mode of the output capacitance through a built-in 120 Ohm resistor. When the regulator is turned off, the current consumption is reduced to 100 nA, while the control current on the Enable line is only 10 nA. The TLV73333P stabilizer has protection against overheating, short circuit and input voltage drop below a certain value. The TLV73333PDBVT chip is available in the popular SOT-23-5 package. If you need to minimize the PCB, you can choose the 2x1 mm X1SON package (TLV73333PDQNR). The TLV733P series includes integrated voltage regulators with low voltage drop and fixed output voltage from the range: 1,0; 1,1; 1,2; 1,5; 1,8; 2,5; 3,3 V.

Other interesting news:

▪ LED textile

▪ BlackBerry owners can chat for free

▪ Ordinary dogs accepted the robot into their company

▪ Mystery of natural mushroom factory solved

▪ Photocells for indoor use

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Tools and mechanisms for agriculture. Article selection

▪ article And the smoke of the fatherland is sweet and pleasant to us. Popular expression

▪ article What historical events were affected by the appearance of several Suns in the sky? Detailed answer

▪ Article Aspiano officinalis. Legends, cultivation, methods of application

▪ article High-quality notch filter on transistors. Encyclopedia of radio electronics and electrical engineering

▪ article VHF FM radio station. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024