JP2007109787A - Contactless dc galvanometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contactless DC galvanometer including a transformer structure that can detect a ripple corresponding to the primary DC current of a DC line 1 to be measured with a secondary coil, and can measure large current of DC current in contactless manner. <P>SOLUTION: The mutual induction coupling factor K between a pair of coils (3, 4) with a core 5 interposed is kept minimized by the excitation and DC bias of the core 5 by a DC excitation coil 2, and it is eased by the excitation of the core 5 by a primary DC current in the offset direction, thereby measuring a DC current value on the primary side by using current induced by a detection coil 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-contact type DC current galvanometer.

  Transformers that measure high voltage and large current with alternating current are called instrument transformers and current transformers, respectively.

  In transformers and current transformers, the voltage and current of the primary winding are induced in the secondary winding, and the voltage and current are measured by a meter connected to the secondary winding.

  The current transformer disclosed in Patent Document 1 is used for improving the magnetic permeability, controlling the DC bias coupling coefficient, etc., and is used for improving accuracy, and this relates to a current transformer for an AC circuit. Therefore, it is not a DC current transformer for a DC circuit. Therefore, it is a DC current transformer and cannot be shared.

  Next, the contact-type voltage drop method is usually used for DC circuit current transformation, but this is an extremely simple structure and has been used for a long time. Therefore, it is a contact and the shunt is simple but this is a problem.

  In addition, the newly developed products that have been commercialized in the market are those that use Hall elements.

This Hall element itself is a DC converter element with a very small shape, the detection part is a point, and in a current transformer in the case of a large current, the cross section of the magnetic core is large, and the magnetic flux of the entire cross section is represented by the point. Since the slits are provided and embedded, there is still room for development in the accuracy of DC conversion.
Japanese Patent Laid-Open No. 5-29167 (FIGS. 1 and 8)

  Therefore, the present invention aims to provide a non-contact type DC current transformer including a transformer function, and utilizes the saturation characteristic of the magnetic core for the measurement of the primary current to be measured. The coupling coefficient between the coils is changed, and the direct current is measured from the detection coil.

  This first means includes a pulsation exciting coil in which a pulsating current including pulsation flows, a detection coil for detecting and displaying a primary DC current, and saturation of a magnetic core. A DC excitation coil for a DC bias is wound around an annular magnetic core, and a non-contact type DC galvanometer is connected to a DC line to be measured having a single-winding primary DC current passing through the center of the magnetic core. Composed.

  The second means is a DC bias generated by excitation of the DC excitation coil. The coupling coefficient between the pulsation excitation coil and the detection coil is minimized by the magnetic saturation characteristic of the magnetic core, and is opposite to the excitation direction of the DC excitation coil. The pulsating voltage induced by the pulsation excitation coil in the detection coil is increased by changing the permeability of the annular magnetic core by the flowing primary DC current so that a magnetic field in the direction of Therefore, the primary DC current can be detected and displayed.

  In the third means, the power source for pulsating wave excitation rectifies a rectangular wave alternating current in a half-wave rectification in a commercial alternating current region that can be generated also for direct current excitation as well as the pulsating wave, and uses this as it is. If AC full-wave rectification is performed, the output is simply a DC current and cannot perform the function of the present application.

  According to the present invention, a non-contact type DC current galvanometer including a transformer function is provided. A pulsating wave corresponding to the primary DC current is induced in the detection coil via the annular magnetic core, and a large current is detected and measured.

  Embodiments of the present invention will be described below with reference to the drawings. However, even if there are specific descriptions in the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment, the present invention is not intended to be limited thereto.

  FIG. 1 is a conceptual diagram of a non-contact type direct current galvanometer of the present embodiment. This non-contact type DC current galvanometer includes a DC power source 21, a DC bias pulsating power source 31, an annular magnetic core 5, and a DC exciting coil 2 that is wound around the annular magnetic core 5 and flows a DC current from the DC power source 21. A pulsation exciting coil 3 that is wound around the annular magnetic core 5 and flows a pulsating current from a DC bias pulsating current source 31; 1 and a detection coil 4 that is wound around an annular magnetic core 5 and detects primary DC. In this non-contact type DC current galvanometer, the excitation coefficient of the DC excitation coil 2 minimizes the coupling coefficient between the pulsation excitation coil 3 and the detection coil 4 so that the DC current flowing in the DC excitation coil 2 is in the opposite direction. The coupling coefficient is increased by the flowing primary direct current, and the current induced in the detection coil 4 is detected. Here, the magnetic field that the DC exciting coil 2 excites the annular magnetic core 5 excites the annular magnetic core 5 to a saturation value, and the DC wire 1 is larger than the magnetic field that excites the annular magnetic core 5, and the direct current is set to a predetermined value. The pulsation waveform is also set to a predetermined waveform. The waveform of the pulsating current is a half-wave rectified waveform of a sine wave or ideally a rectangular wave.

  Here, the operation principle of the non-contact type DC current galvanometer of the present embodiment will be described.

  In the excitation by the direct current of the annular magnetic core 5, the magnetic permeability μ (= B / H) until the magnetization of the magnetic core reaches saturation varies depending on the value of the primary direct current flowing through the direct current line 1.

  FIG. 1 is a magnetic permeability characteristic curve showing a change in the magnetic permeability μ when a high magnetic permeability annular magnetic core 5 such as Permalloy is magnetized by a DC magnetic field H. μ is μi when H is zero, and increases as H increases to reach the maximum value μm. When the annular core 5 is magnetized to saturation by H, it rapidly decreases, and when saturation magnetization is reached. μf is smaller than μi. The present invention uses this relationship between μ and H.

  When the magnetic permeability of the annular magnetic core 5 becomes μf due to the DC magnetic field H generated by the DC excitation coil 2, the mutual induction coupling coefficient K between the pulsation excitation coil and the detection coil also becomes the minimum value. In this state, when the magnetic permeability is restored from μf to near μm by a direct current magnetic field of primary direct current (direct current), the coupling coefficient K changes from the minimum value to the maximum value. Therefore, the primary DC current can be measured by detecting the current of the detection coil 4 within that range (in the range from point a to point B shown in FIG. 2). Here, the range from the point a to the point B is a range where the magnetic permeability changes substantially linearly, and the coupling coefficient K also changes substantially linearly.

  At point a, a half-wave rectified current or a rectangular wave current is passed through the pulsation exciting coil to excite the annular magnetic core 5, so that the detection output rises slowly when the detected current is near zero. The region with good linearity is a region from point A to point B shown in FIG. As described above, the mutual inductive coupling coefficient K between the pair of coils (the pulsation excitation coil 3 and the detection coil 4) changes depending on the value of the direct current flowing through the direct current excitation coil, and becomes a small value as the magnetization reaches saturation. Thus, the pulsating current of the pulsation exciting coil 3 is hardly induced in the detection coil. Therefore, the non-contact type DC current galvanometer of the present invention is in a state in which the induction of the pulsating current is suppressed by the saturation magnetization of the annular magnetic core 5, and the coupling coefficient is relaxed by exciting the annular magnetic core by the measured DC ( And a structure for detecting and measuring this. The present invention uses the state of magnetization applied to the annular magnetic core 5 as a detection medium as described above, and the characteristic of the annular magnetic core 5 is a soft magnetic material. It is a condition that the magnetic material is capable of ignoring hysteresis. Then, in order to detect the primary DC current, the degree of progress of magnetization of the annular magnetic core 5 is detected, and in order to obtain the reference value, the DC exciting coil 2 is wound and the annular magnetic core 5 is DC excited. The other pair of coils refers to a pulsation exciting coil 3 that is excited by a pulsating current through an annular magnetic core 5 and a detection coil 4 in which the voltage of the pulsating current is induced. Here, if the annular magnetic core 5 is excited by the direct current component of the rectified current flowing through the direct current excitation coil 2, the coupling coefficient K between the pair of coils changes substantially linearly, and the annular magnetic core 5 reaches a saturated state. In this state, if the coupling coefficient responds linearly with the primary measurement current, a voltage due to the pulsating current is induced in the detection coil 4. However, since the effect of suppressing the coupling coefficient K cannot be obtained only by the rectified current, compensation (DC bias or the like) that enhances DC excitation is required. In the state in which the above compensation is performed, if the DC excitation of the annular magnetic core 5 by the current flowing through the DC wire 1 is in a direction that cancels the above-described constant DC excitation, the primary DC current value can be detected by the detection coil 4. Become. Here, the excitation characteristics of the magnetic core and the coupling coefficient between the coils can be converted linearly, or, of course, the primary DC current value is converted linearly, as long as it is a linear conversion overall. If so, it may be called a so-called measurement DC current non-contact type DC current galvanometer, not just a sensor. The excitation of the pulsating current exciting coil 3 is a current immediately after the rectification of the alternating current, and the pulsating current is also a direct current pulsation. The induced voltage to the output detection coil due to this pulsation becomes a pulsed AC voltage. The DC excitation after cancellation is detected by a change in the DC bias applied to the coil. If excitation is performed with a commercial AC voltage, the AC half-wave (eg, negative voltage) cancels the bias due to the positive half-wave, and becomes inefficient. In the present invention, excitation is effective by using AC half-wave rectification or further using a rectangular wave. When a primary DC current flows through the DC line to be measured, the direct current excitation causes the magnetization of the magnetic core to be relaxed, the coupling coefficient between the pair of coils increases, and the primary DC from the induced voltage value to the output detection coil. Since the current value can be detected by the output detection coil, a DC non-contact type DC current galvanometer is configured. In this case, the excitation of the annular magnetic core has a pulsation immediately after rectification, and is not a smooth direct current, so that the rise of the output direct current near zero shows a slow nonlinearity. In order to obtain a linear characteristic, it is easy to compensate for a non-linear portion near the output zero (range from a to A in FIG. 2) by exciting only the rising portion of the annular magnetic core with a smooth DC power source. By the way, it is difficult to make the coupling coefficient between the pulsating AC coil and the output detection line completely zero by saturating the magnetic core with only the rectified current of the AC current. However, if the output detection circuit is compensated to a value near zero by the comparison circuit, the transition to the zero point is easy.

  As mentioned above, although embodiment of this invention was described, although this invention utilizes the structure of a transformer, it is clear that a large current and a high voltage can also be measured.

  In FIG. 1, each coil is illustrated in a concentrated manner, but actually, the coils are overlaid in several layers over the entire annular magnetic core 5. The entire structure of the non-contact type DC current galvanometer has a simple shape, and only a single-winding DC wire 1 passes through the center portion thereof. However, since each coil may be concentrated winding, a measuring clamp structure such as a DC line can be used.

  Fig. 3 is a schematic diagram of a non-contact type DC current galvanometer when a half-wave rectification is used as a pulsating flow in a prototype. 6 is a half-wave rectifier such as a diode. The coil 2 and the coil 4 are wound over the entire surface of the annular magnetic core 5 as in FIG. The outer diameter after the winding was φ22 mm, the inner diameter was φ8 mm, and the thickness was about 12 mm. The linearity compensator was omitted.

  FIG. 4 is an output characteristic curve of a non-contact type DC current galvanometer when half-wave rectification is used as a pulsating current waveform (see FIG. 3). The output current characteristic is approximately equal to the primary DC current. It is a 150A characteristic curve that is linear and shows the relationship with the primary DC current (DC current to be measured) when the rectification excitation current is changed.

It is the schematic of a non-contact type direct current galvanometer. It is a permeability change curve of a high permeability annular magnetic core. It is a conceptual diagram of the non-contact-type direct current galvanometer which uses the pulsating current of a half-wave rectification waveform. It is an output characteristic curve which shows an example of the characteristic of a non-contact-type direct current galvanometer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC line to be measured 2 DC excitation coil 21 DC power supply 3 Pulsed excitation coil 31 DC bias pulsating power supply 4 Detection coil 5 Annular magnetic core 6 Half-wave rectifier 7 Ammeter

Claims (3)

DC power supply,
DC bias pulsating power supply,
An annular magnetic core,
A DC exciting coil wound around the annular magnetic core and for passing a DC current from the DC power source;
A pulsation exciting coil that is wound around the annular magnetic core and flows a pulsating current from the DC (hereinafter referred to as DC bias) pulsating current source;
A direct current line passing through the center of the annular magnetic core and passing a primary direct current of a single winding structure;
A non-contact type direct current galvanometer comprising a detection coil wound around the annular magnetic core and detecting the primary direct current,
Due to the saturation of the magnetic core of the DC excitation coil and the DC bias, the coupling coefficient between the pulsation excitation coil and the detection coil is minimized,
The coupling coefficient is increased by the primary direct current flowing in the direction opposite to the direct current flowing in the direct current excitation coil,
A non-contact type DC current galvanometer which detects a current induced in the detection coil. The magnetic field that the DC exciting coil excites the annular magnetic core excites the annular magnetic core to a saturation value, and the DC wire is larger than the magnetic field that excites the annular magnetic core,
The non-contact type direct current galvanometer according to claim 1, wherein the direct current is set to a predetermined value, and the pulsation waveform is also set to a predetermined waveform.   The non-contact type DC current galvanometer according to claim 2, wherein the predetermined waveform of the pulsating current is a pulsating waveform of a half-wave rectified waveform of a sine wave alternating current or a rectangular wave alternating current.

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