Static characteristics of contactless converters of monitoring and control systems

The paper substantiates the need to use non-contact conversion and measurement of large direct currents using magnetic modulation contactless transducers of increased sensitivity for land reclamation, irrigation, industry, metallurgy and agriculture and water management in general, and the results of their design development are presented. It is shown that the developed converter, in contrast to the known ones, has increased accuracy and sensitivity, a technologically advanced design and low weight and dimensions with low material consumption and cost. Characteristics of information non-contact magnetic modulation converters statically are considered. It is shown that the value of the excitation value corresponds to a certain maximum value of the measured value. In this case, the maxima of the measured value, increasing in value with an increase in the excitation value, are shifted towards the increase in the measured value. The discrepancy between the experimentally and theoretically obtained static characteristics of the converter does not exceed 6 percent. The developed converter can be widely used in electrical systems in land reclamation and irrigation, in water supply, industry, railway transport, science, technology, and for checking electric meters at their installation site for contactless control of direct and alternating currents.

It was revealed that the instability of the current control systems, the presence of additional resistances due to the oxidation of the contacts lead to a decrease in the performance of electrical installations, to downtime, and large voltage drops on the shunts lead to unjustified power losses.
As a result of the analysis of the conducted studies, an urgent need was revealed at many industrial enterprises and in farms in the irrigated agriculture zone of the Republic of Uzbekistan in the non-destructive contactless control of LDC with a value from 100 A to 30 kA using both portable and stationary measuring transducers (MT) with an error of 1 -3 %, using in several cases multi-range, as well as with a flexible, integrating circuit of IP nondestructive testing LDC [2], [12][13][14][15][16][17][18][19][20][21][22][23].

Materials and methods
The ever-increasing requirements for the elements and technical means of monitoring and control systems in the electric power industry, railway transport, as well as agriculture have led to the development of energy-saving contactless magneto-modulation converters of large direct currents with detachable integrating circuits (MNT), which allow for wrapping around the device without violating the structural and circuit integrity conductors with convertible LDC [3 -5].
As a result of the analysis of places, transducers and devices for non-destructive noncontact control of high currents, the main requirements for MNT were identified [6 -31]. These include high accuracy, reliability, sensitivity, low weight, dimensions, material consumption and cost, manufacturability of design, absence of errors from the influence of external magnetic fields, return conductor with current, displacement of the conductor with current from the center of the integrating circuit, ferromagnetic masses, no consumption energy from the measured circuit, the ability to work in an aggressive environment, explosion safety, as well as the absence of a galvanic connection between the controlled direct current and the measuring circuit and the presence in some cases of the possibility of fixed regulation of the sensitivity of the MNT in a wide controlled range and the manufacture of the MNT as portable or stationary [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39].
We have developed several universal energy-saving non-contact galvanomagnetic converters of large direct currents, allowing without breaking the circuit to convert both direct and alternating large currents in various monitoring and control systems, in which the tasks are solved by using special designs of detachable closed magnetic circuits with transverse and longitudinal distributed magnetic parameters and increased path length of the working magnetic flux over steel [2].

Results and Discussion
One of the developed IBE is information non-contact magneto-modulation converter of large direct currents, partially shown in Figure 1 with basic dimensions. This design was developed based on the IP [8] and is an MNT with transversely and longitudinally distributed magnetic parameters... It features increased sensitivity and an extended range of converted currents. IBE contains a detachable closed magnetic circuit 1, consisting of two identical halves 2 and 3, each of which, in turn, consists of separate ferromagnetic elements made in the form of trapezoids with the same gaps between them. Each ferromagnetic element has two through holes, through each of which a modulation winding is wound, consisting of sections 4 and 6. Sections 4 and 6 are connected in series and according to. A measuring winding 5 is wound between the through holes over the modulation winding 5. All measuring windings are connected in series and closed to the measuring device. The modulation windings are also connected in series and connected to a stable AC source (not shown in Figure 1). To freely grip the bus 7 with a controlled current, the closed magnetic circuit 1 is made detachable. The series connection of the modulation windings 4 and 6 with each other in the presence of alternating current in them and the arrangement of the measuring windings 5 in the intervals between the through holes in the ferromagnetic elements allowed to carry out longitudinal modulation of the magnetic resistance of the magnetic circuit on the path of the working flow Ф, created by a controlled direct current, and induce an EMF in the measuring windings 5, depending on the converted direct current. The developed MNT can also control alternating current. There should be no alternating current in sections 4 and 6 of the modulation winding in this case. The expansion of the upper limit of the controlled direct current in the developed design of the MNT is carried out by increasing the length of the working magnetic flux along the steel of the magnetic circuit elements and including transverse and longitudinal air gaps in its path, i.e., the implementation of a split magnetic circuit with transversely and longitudinally distributed magnetic parameters.
To control the LDC, the MNT detachable magnetic circuit covers the bus 7. Due to the modulation ampere turns, the detachable magnetic circuit is saturated during each halfperiod of the supply voltage. In this case, the permeability of the magnetic circuit for the longitudinal field created by the controlled current decreases sharply. At the moment when the modulation current passes through zero, the magnetic core permeability rises to the initial value. Thus, with the stability of the modulation ampere turns, an EMF of double frequency will be induced in the measuring winding, which depends on the controlled current.
With the mutual movement of halves 2 and 3 of the detachable magnetic circuit of the MBP, the size of the gaps between the trapezoids changes, leading to a change in the whole of the magnetic resistance of the magnetic circuit on the path of the working magnetic flux Ф created by the controlled direct current. This leads to changing the limits of the controlled current, i.e. allows you to make the MBE multi-limit.
To analyze the main characteristics of the MBE and its calculation, it is necessary to express the static characteristics of the MBE. To determine the expression of the static characteristics of the MBFP (Figure 1), let us single out one of its elements (Figure 2). Let's divide it into two halves: upper 1 and lower 2. At the moment when the current of the excitation windings I~ has the direction shown by the arrow, the magnetic field strength Н~ created by this current in the upper half of the element coincides with the direction of the magnetic field strength, measured current Ii. On the contrary, in the lower half of the element, the direction Н~ is opposite to the direction of Н и . Therefore, one can write (1) In the next half-period, the direction of the field strength H~ changes. Approximating the main magnetization curve by the sum of the trigonometric arctangent and the straight line with the slope Fig. 2 where а 1 , а 2 , а 3 are the approximation coefficients, and substituting (1) and (2) into (3), we obtain a (H u -H~); (5) Here, the field strength from the excitation current is H~ = H m~t  sin ... (6) Where in where H m~, I m~ are amplitude values of field strength and excitation current; w~ is the number of turns of the excitation winding IBE; l Wed is the average length of the line of the field strength of the excitation element of the MBP.
The initial equation for the output EMF of the MNT has the form The cross-section S of the two halves of the element, participating in the induction of the EMF in the measuring winding, having the total number of turns w u , is determined from Figure1 in the form Where: h 1 is the thickness of the set of the magnetic circuit element; v is the width of the magnetic circuit element; d is the diameter of the hole for the field winding.
Substituting the values of magnetic inductions (4) and (5) into (8) and taking into account (6), we find Let us introduce the notation of the measured quantity  (11) and excitation values 2 а Н М  H m~, (12) which are dimensionless since the coefficient a 2 has the inverse dimension of the magnetic field strength.
Then expression (10) can be rewritten as The resulting expression is a periodic non-sinusoidal function, so the average value of the output EMF is We denote sin ω t = Z, then ωcos ωt dt = d Z , respectively, the limits of integration at t 1 = 0 will be Z 1 = 0, and at Substituting the accepted designations and limits of integration into (14) and integrating, we obtain Here E b is the base value of the output EMF, equal to The output EMF of the converter in fractional values is  Fig. 3. The value of the magnitude of the excitation of the H M corresponds to a certain maximum value of the measured value H xM . In this case, the maxima of H xM , increasing in value with increasing Н М , are shifted towards increasing H x . The experiments performed showed that the discrepancy between the experimentally (curve 2) and theoretical (curve 1) obtained static characteristics of the MNT does not exceed 6 percent.

Conclusions
Informational contactless converters have been developed for modern control and management systems in water supply, land reclamation, irrigation, as well as solar and laser technology, renewable energy sources, industry, agro-industrial sphere, characterized by an extended controlled range of converted direct currents with small dimensions and weight, increased accuracy and sensitivity, simplicity and manufacturability of the design with low material consumption and cost and the possibility of contactless control of direct and alternating currents with an error of 1.5%, as well as for control of electricity and verification of electricity meters at their installation site. The static characteristics of information contactless magneto-modulation converters are considered. It is shown that the value of the excitation value corresponds to a certain maximum value of the measured value. In this case, the maxima of the measured value, increasing in value with an increase in the excitation value, are shifted towards the increase in the measured value. The discrepancy between the experimentally and theoretically obtained static characteristics of the converter does not exceed 6 percent.