HU189699B - Magnetic voltmeter for measuring current - Google Patents

Abstract

Field of the Invention The present invention relates to a magnetic voltage meter for measuring current, which is composed of a coil bent to the shape of a ring having a number of nearly identical alignment joints and a ring having an almost identical induced voltage. The coils are coaxially and coaxially arranged so that their joint joints are rotated at an angle of 2 rr / n to each other, and that the joint clearance of two adjacent coils is twisted relative to one another by a tr angle. The coils are connected in series so that the induced voltage is added. -1-

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic voltage meter for current measurement which, in addition to being openable, has low interference sensitivity.

The principle of magnetic voltage measurement was first published hundreds of years ago (Chattock, A.P.: On a Magnetic Potentiometer - Phll. Mag. And I. of Science. Bánd 24. 1887, pp. 94-96). The first magnetic voltage meters are approx. They are made of wire evenly wound onto a flexible insulating tape 50 cm long. In the case of a coil, the magnetic voltage difference between the ends of the coil; current. Initially, coils made only for magnetic voltage measurement were increasingly used for current measurement. As most currents (excitation currents) of high-current rails or cables are to be measured, it is expedient to make the measuring coils in divisible or open versions, which at the same time satisfy the requirement of simpler manufacturing. The latter requirement was generally not a priority because these individually or in small series rolls had to meet the requirements of accurate measurement. Thus, only subordinate to this purpose was the need for ease of manufacture and other requirements (eg space requirements).

The ideal magnetic voltmeter for current measurement meets the following accuracy criteria:

1. The voltage induced in the measuring coil is independent of the mutual position of the measuring coil and its conductors and of

2. the rate of change of the excitation current;

3. external excitation conductors outside the coil do not induce voltage in the measuring coil (interference voltage).

The second criterion is automatically met at a fixed earth-moving current (eg, sinusoidal AC). Among the first third criteria, we satisfy the other by satisfying the other. These criteria can be met with the accuracy of any distance when the magnetic voltmeter and the excitation current are fixed relative to each other. In practice, however, there is a limit to increasing the radius of r ', so staying within this size range requires the magnetic stress meter itself to be approached at least to the degree of accuracy required.

One of the prerequisites for meeting the accuracy criteria is that the closed measuring coil be made of either straight-axis coils or coils with a constant curvature (circular) axis. The excitation conductor is made of straight-axis coils and a circular opening-type magnetic tension gauge that does not overlap the excitation conductor. Because of the joint gaps between the individual coils, such magnetic voltmeters do not meet the first and third accuracy criteria.

In the past, additional threads or rolls have been placed near the end of the coil to reduce errors due to joint gaps. The effectiveness of these methods depends greatly on the magnetic field distribution near the coil ends. Since this field distribution is a function of the mutual position of the measuring coil and the excitation wire, the accuracy criteria for current measurement are not met by using additional threads or coils. Magnetic voltage meters made up of straight-axis coils

A Physically Validated Method for Reducing Error due to Fitting Gaps Koppelmann Nov 1960 Patent No. 3, D.B.P. 1079192, is incorporated herein by reference. According to this, the joint gaps were magnetically shielded by placing the coils in cavities formed in iron plate packages. Using Method A to Measure Current for High Voltage Magnetic Voltage Meters. However, their dimensions increase significantly with the increase of the current. Magnetic shielding is effective only until the shielding iron begins to saturate due to the field strength generated by the excitation conductor. For higher geothermal currents, the shading plate package should be located away from the internal and external excitation conductors. Because the saturation of the shielding iron also depends on the position of the excitation wire, this solution can only meet the accuracy criteria up to a certain excitation current value. This limit current corresponds to the current flowing in the excitation conductor on the surface of the shielding plate package. The effective value of the 50 Hz cut-off current is approx. 3-4 kA. Magnetically shielded magnetic voltmeters for higher excitation currents are therefore not ideal and have large geometric dimensions. It can thus be stated that no additional threads or coils can be used to reduce faults in the joint gap and that the magnetic shield is only applicable for excitation currents of less than 3-4 kA. Another disadvantage of these solutions is that the geometric dimensions of the magnetic voltmeter are increased without increasing sensitivity.

Recently, the protection of 50 Hz AC equipment against overload and short circuit has been increasingly provided by electronic protections. Current encoders for defense purposes these solutions must have a linear transfer characteristic wide power range (10-10 ⁵⁾ accuracy of a few% so geijesztőárammal provide a proportional voltage signal. Only small transducers of small geometric size can be made while maintaining the high value of proper transmission of small currents. Their dimensions have to be adapted to the current path and phase distance of an electrical appliance (eg circuit breaker). The current transducer covering the high current conductors (eg the wires of a circuit breaker) must also be of a demountable design so that it can be mounted on a conductor with connecting fittings (eg terminals). These requirements of protection are no longer met by the magnetic voltage meters used to date and other types of current transmitters do not provide the solution.

Our aim was to achieve linear, high sensitivity and small

We develop a removable magnetic tension gauge with geometry dimensions that meets the precision criteria as required and meets the requirements of ease of manufacture.

The invention is described in the drawings. The attached drawings show

Figure 1 shows an arrangement of coils of a magnetic voltage meter according to the invention, a

Fig. 2 is a magnetic tension meter according to the invention having an insulating cover and a

Figure 3 shows the same magnetic voltage meter mu-21

189,699

Route it to the path of a circuit breaker in the mounted position

The essence of the magnetic tension meter according to the invention consists in a general arrangement of n coils (n = 2, 3,4, ..) coaxially arranged in an overlapping annular shape, differing only in their curvature. The center lines of the joints of these coils are rotated by 2 ff / n relative to one another. For even n, the center lines of the joining gaps of two adjacent coils are rotated with respect to each other at an angle rr. 1 shows a specific arrangement composed of coils n = 4

Here is an example. The winding applied to a core of constant cross-section made of flexible insulating material in one or more layers forms the innermost first winding 1, the surrounding second winding 2, the third winding 3 surrounding the second winding 2 and the fourth outermost fourth winding. These are connected in series so that the voltages induced in them are added. For example, in the same direction of travel, the end of the first winding 1 is connected to the beginning of the second winding 2, the end of the second winding 2 to the beginning of the third winding 3, the end of the third winding 3 to the beginning of the fourth winding 4. the end of the fourth roll. The joints are designed so that conductive loops with a smaller surface area are formed (e.g., by bipolar current conduction). Between the ends of the first coil 1 there is a first joint gap h1, a second joint gap h2 at the second coil 2, a third joint gap h3 at the third coil 3 and a fourth joint gap h4 at the fourth coil 4 with center lines 2π / n apart. , ie in our case they are rotated at n = 4 by ff / 2. The center lines of the first joint gap h1 and the second joint h2, and the third joint gap h3 and the fourth joint gap h4 are rotated with respect to each other by an angle ff.

A cover made of insulating material may be used to secure, mechanically protect and electrically insulate the coil arrangement shown in Figure 1. Figure 2 shows a possible embodiment of a magnetic voltage meter according to the invention with an insulating cover. The lower cover 5 and the upper cover 6 are snap-in. A bifilar curled flexible insulated conductor serves for the 7 terminals.

The correct operation of the magnetic strain gauge of the present invention requires that the same voltage be induced in the coil n (if each coil differs in curvature only, this condition can be approximated) and the n joint gap is approximately the same. In this case, the inaccuracy resulting from the joint gap of a coil appears to be less than n-th in the value of the resulting voltage. Increasing the value of n beyond all boundaries would effectively eliminate the error-causing effect of the joint gaps; such a magnetic tension meter would fully meet the first and third accuracy criteria for the joint gaps. Open rolls can be simply produced by winding the cores made of flexible insulating material in an expanded, linear axis and then bending them into a ring shape. Using this method, the radial size (thickness) of the coils is rather small, depending on the bending curvature. Nor can the width of the roll and the number of layers of the winding be increased arbitrarily, so that the sensitivity can only be increased by n the number of rolls. Thus, the use of multiple coils is justified not only by precision but also by the design which can be opened, and by the resulting simple manufacturing technology and appropriate sensitivity. The requirement of spatial symmetry essential for accuracy is best met if the joint gaps are relative to each other. They are rotated by π / η. Because of the symmetry, it is advantageous to use an even number of coils. In this case, however, care must be taken to ensure that the joining gaps of the two adjacent coils are rotated with respect to each other, so that a more symmetrical arrangement is obtained.

The advantage of the magnetic voltage meter according to the invention is that it combines the following features: a., Openable (mounted on a conductor without breaking it), b., High accuracy and low disturbance sensitivity, c., Small geometric dimensions, d., High sensitivity, e. ., linear signal transmission. Based on these properties, the magnetic voltage meter of the present invention can perform tasks that have not been technically accomplished yet, or only in a complex manner, at a high cost. An example of such an application is shown in Fig. 3, where the magnetic voltage measuring unit 8 of Fig. 2 is mounted in the track section 9 of the auxiliary circuit of a low-voltage 1000 A rated circuit breaker.

Claims (1)

A patent claim Magnetic voltage gauge for current measurement, wound on a core of flexible insulating material having a constant thread density in one or more layers and having a joint gap (first joint gap, second joint gap, third joint gap, fourth joint gap), 3,4 ... consists of different coils only in their curvature (first coil, second coil, third coil, fourth coil ...), characterized in that the number n coils are arranged in a comprehensive and coaxial manner such that the coils the centerline of the joint joints formed by 2 ff / n, in the case of even n, the center line of the joint joints of two adjacent coils is rotated with respect to each other, and the coils are connected in series such that the induced voltage is applied thereto in the specific case of ode and n = 4, the first coil (1) is coaxially intercepted by the second coil (2), the second coil (2) by the third coil (3), the third coil (3) by the fourth coil (4) that the first joint gap formed by the first roll (1), the second joint gap (h2) formed by the second roll (2), the third joint gap (h3) formed by the third roll (3) and the fourth roll (4), the center lines of the fourth joint gap (h4) are rotated with respect to each other by an angle ff / 2, and the first joint gap (hl) é * the second joint gap (h2) and the third joint gap hι3) and the fourth joint the rotation angle ff between the center lines of the gap si (h4) can be measured; 189,699 connecting the end of the second coil (2) to the beginning of the third coil (3), connecting the end of the third coil (3) to the beginning of the fourth coil (4), the terminals of the magnetic voltage gauge beginning of the first coil (1) and It is formed.