SU1185253A1 - Electric current meter in a conductor - Google Patents

Description

The invention relates to electrical engineering and can be used for contactless measurement of large constant currents.

The purpose of the invention is to improve the measurement accuracy.

FIG. 1 schematically shows the structure of the device; in fig. 2 is a block diagram of the device; Figs 3 and 4 show the interaction of magnetic currents with 10 currents for different directions of controlled current.

The meter contains one (Fig. 1) magnetic core 1, covering the conductor 2 with a controlled current. A magnetically sensitive transducer is placed in the 5, 5 core of the magnetic circuit 1 between its ends 3 and 4 and consists of a flat elastic ferromagnetic plate 5 with output elements installed on its 20 opposite planes - resistance strain gages 6 and 7. The plate 5 is fixed console at one end and freely covered winding bias 8, made of a wire from a material with a large temperature coefficient of resistance, for example, copper or nickel, the resistance strain gages 6 and 7 form the two arms of the measuring bridge 30 (figure 2), two others GIH shoulder are formed by stable resistors 9 and 10 '. The measuring bridge with its diagonal in series with the winding 8 bias is connected to a DC source (not shown in figure 2). The amplifier 11 is connected to the measuring diagonal of the measuring bridge, the pointer 12 is connected to the output of which.

The device works as follows.

In the initial state, in the absence of a controlled current in the conductor 2 (Fig. 1), the ferromagnetic plast-45 is 5-magnetized with a constant current to supply the measuring bridge and occupies a middle position in the gap of the magnetic circuit 1, i.e. not 'deformed. In this case, the resistance of the ten-50 resistances 6 and 7 are equal and the measuring bridge is balanced (figure 2).

When a controlled current appears in conductor 2 in magnetic core 1, a magnetic flux F _and 55 appears (FIGS. 2-4), which closes through the air gap of magnetic circuit 1. The interaction of this flux Fc with

the flux of magnetization Φ _{and the} plate leads to the appearance of an electromagnetic force = K F _N F _N acting on plate 5 (K is a constant coefficient depending on the size and properties of the ferromagnetic plate).

Under the action of this force, the plate 5, being deformed, deviates, as shown in Fig. 3 and 4, to the end 3 or 4 of the magnetic circuit 1, depending on the direction of flow F, i.e. directions of the monitored current in the conductor 2. At a constant flow Φ _{n, the} strain value of the plate 5 is proportional to the flow Φ _n and is a measure of the monitored current. Strain gages 6 and 7 convert this deformation into a proportional difference of their resistances, • which the measuring bridge transforms into a proportional voltage taken from the measuring diagonal of the measuring bridge. This voltage is amplified by the amplifier 11 and registered with the help of the pointer 12.

The device automatically compensates for the temperature error, which occurs as follows.

Suppose, for example, at a certain constant value of the monitored current that the ambient temperature rises from a normal value, which causes a decrease in the rigidity of the ferromagnetic plate 5. This would cause an increase in the deformation of the plate 5 and a corresponding increase in the voltage taken from the measuring diagonal of the measuring bridge. But with increasing temperature the resistance of the bias coil 8 increases, decreases and the current therethrough decreases _{to the} flow F so that the deformation plate 5 remains unchanged. As the temperature rises, the resistances of the strain gauges 6 and 7 simultaneously increase and, consequently, the difference of their resistances, which would also lead to an increase in the voltage taken from the measuring diagonal of the measuring bridge. However, due to the fact that the bias winding 8 is connected in series to the supply diagonal of the measuring bridge, then with increasing resistance of this winding 8

3

also decreases the current supply of the measuring bridge and the voltage removed from the measuring diagonal of the measuring bridge remains unchanged. Similarly, the compensation of temperature error and at lower ambient temperatures. With conformance1185253 4

By selecting the parameters of the device elements, the temperature error is automatically almost completely compensated.

Thus, an increase in the accuracy of the proposed device in comparison with the known is achieved.

1185253

Claims (2)

ELECTRIC CURRENT IN A CONDUCTOR, containing a magnetic conductor, covering a current-controlled conductor, a magnetically sensitive transducer, having two identical output elements placed in the gap of the magnetic conductor, included in the measuring bridge shoulders, one output of the diagonal supply of which is connected to one pole of a direct current source, an amplifier the input of which is included in the measuring diagonal of the measuring bridge and the pointer connected to the output of the amplifier, characterized in that, in order to increase t measurement, the magnetically sensitive transducer is made in the form of an elastic ferromagnetic plate placed in a magnetic core gap, cantilevered at one end, and the output of the resistive magnetically sensitive transducer is mounted on opposite planes of the specified ferromagnetic plate, which is freely covered by an “additionally inserted bias winding made from material with a large positive temperature coefficient of resistance, pr And what one winding terminal is connected to the second terminal of the supply diagonal of the measuring bridge, and its other terminal is connected to the second pole of the DC source. 81) „1185253 > one 1185253 2