To the issue of experimental research of static characteristics of reed switch converter

ABSTRACT

In this paper, reed-switch displacement transducers with longitudinal movable screens and transverse movable magnets, as well as transducers of large direct currents, were subjected to experimental research.

АННОТАЦИЯ

 В данной работе экспериментальным исследованиям подверглись герконовые преобразователи перемещений с продольными подвижными экранами и поперечными подвижными магнитами, а также преобразователи больших постоянных токов.

Keywords: Structure diagrams, parameter, sensor, magnetic circuit

Ключевые слова: Структурные схемы, параметр, датчик, магнитопровод

A magnetic circuit and a movable screen were used, the dimensions of which are shown in Fig. 1, the brand of the used reed switches KEM-1, KEM-2, resistors forming discretely varying conductivity G₃ were distributed along the magnetic circuit with a quantization step for displacement  mm and had nominal resistance values ​​of 8.5 Ohm, the number of turns of the excitation winding 10000, wire diameter 0.1 mm when powered from a mains source with a frequency of 50 Hz and a voltage of 220 V at a resistance of 8.5 Ohm, the output voltage was 3 V. A class 0.5 voltmeter with a division value of 30 mV was used as a measuring device. Figure 2 shows the results of experiments for the dependence of the output voltage as a function of coordinates of the moving part: the dashed line shows the calculated ones, and the solid line shows the arithmetic mean of the mathematical processing of the experimental results.

Figure 1. Magnetic core and movable screen (used in experimental Research)

Figure 2. Curves of dependence of the output voltage as a function of the coordinates of the moving part

From a comparison of the curves, it follows that the maximum deviation of the experimental curve from the calculated one does not exceed 2.5%. Fig. 2 shows only a part of the static characteristic corresponding to 1/3 of the range of movement of the movable part. Similar curves were obtained for transverse moving magnet transducers shown in Fig. 3, using the same magnetic circuit and the same reed switch system. A distinctive feature of these two characteristics is a significant hysteresis for the arithmetic mean expectations of mathematical processing of the results of the forward and reverse travel of the moving part (the reverse travel is shown by the dashed line in Fig. 3). Analysis of these two characteristics shows that reed-switch converters with a movable screen practically eliminate hysteresis errors.

Figure 4 shows an experimental sample of a DC-current converter using the same reed switches, but located at different distances from the magnetic circuit, covering the winding with the converted current.

Figure 3. Curves for transverse moving magnet transducer

Figure 5 shows the dependence of the numbers of the switched on reed switches on the projected current. Solid lines show discrete changes in closed reed switches with increasing currents, and dashed lines show many closed reed switches with decreasing currents (shaded areas correspond to hysteresis areas).

Figure: 4. An experimental sample of a DC-DC converter

Figure: 5. Dependence of the numbers of reed switches on the DC / DC converter

From the analysis of the curves in Fig. 5. It follows that with an increase in the converted current, the hysteresis area increases and leads to errors exceeding 25% when converting large values ​​of direct currents. To reduce this source of error, each reed switch is covered by a coil under excitation with alternating ampere turns, moreover, the return coefficient of the reed switches increases due to the excitation of the magnetic circuit of the reed switch by an alternating magnetic flux to such a value at which the hysteresis area decreases by an order of magnitude or more with the ratio of amperes of turns of alternating voltage to constant equal to 0.22.

The design of the magnetic system of a reed switch with a movable screen and a movable winding, in which the ratio of the magnetic voltages of switching off and switching on of reed switches can be increased by an order of magnitude or more due to additional ampere turns connected in series and opposite to the main ones. For reed transducers with a movable shield, the additional ampere turns must be offset from the rest by 90 ° in phase.

By analyzing the flux distribution in the magnetic circuit of reed switches, as well as the results of experimental studies, according to which the magnetic disconnection voltage can be reduced to 0.05 of the magnetic switching voltage of the reed switches, the return coefficient increases to 0.8 and more.

Conclusion

The practical significance of the conclusion lies in expanding the functionality of industrially produced reed switches. The theoretical value lies in expanding the field of application of the theory of differential converters.

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