JPH09269337A - Division-type leakage current measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a residual current in a division-type leakage current measuring apparatus which detects a zero-phase current. SOLUTION: Coils A, D and coils B, C are wound respectively on one pair of cores 10A, 10B which become a ring shape when they are faced so to be to brought into contact, the coils A, B and the coils C, D which sandwich dividing faces of the cores 10A, 10B are connected in series, a leakage magnetic flux which is generated by a residual current is captured by combining one pair of coils, and a magnetic coupling state in the cores 10A, 10B and in two dividing faces of a shield is output as an induced voltage. The imbalance of the magnetic coupling state is gain-adjusted by amplifiers 1, 3, and it is phase- adjusted by phase shifters 2, 4 so as to be added by an adder 5 and so as to be displayed on a measuring instrument 6. Thereby, a state that a magnetic coupling balance is obtained in the cores 10A, 10B and in the two dividing faces of the shield is obtained, and an error due to the residual current can be reduced even when the cores 10A, 10B are opened and closed repeatedly in order to clamp a wire to be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a split-type leakage current measuring device for detecting a zero-phase current in an electric circuit, and more particularly to a technique for reducing a residual current at the time of measurement and improving measurement accuracy.

[0002]

2. Description of the Related Art FIG. 2 is a front view of a conventional split-type leakage current measuring instrument, and FIG. 3 is a sectional view taken along the line AA in FIG. The toroidal core 20 is divided into _two semi-annular portions at the dividing surfaces C ₁ and C ₂ , and the divided cores 20A and 20B are provided with coils L.
₁ and L ₂ are wound respectively, the two windings are connected in series, and an output is obtained through a predetermined circuit. An electric wire to be measured is arranged at the inner diameter of the annular core 20 for measurement. 21 is an inner shield for shielding the coils L ₁ and L ₂ to prevent external interference, 22 is a similar outer shield, and 23 is a similar side shield.

In the conventional split type leak current measuring device having such a configuration, in order to accommodate the electric wire to be measured in the annular core 20, the annular core 20 is once divided into the dividing plane C.
₁ , C _{2, and} the wires to be measured are accommodated and arranged again. Then, both cores 20A, 20B are divided again into divided planes C ₁ , C _2.
To perform measurement. Therefore, the division surfaces C ₁ and C ₂ are polished as mirror-finished surfaces to perform bonding without gaps.
Alternatively, a contrivance has been required to reduce the thickness of the plate and improve the magnetic coupling as an overlap fitting method.

In order to improve the residual characteristics, it is of course to improve the magnetic coupling between the divided surfaces C ₁ and C ₂ , but in addition to the two divided surfaces C ₁ and C ₂ , C
_If the balance of ₂ is not achieved, the residual characteristics cannot be improved. For this reason, since the required characteristics cannot be obtained simply in a manufactured state, in the case of a laminated core, the characteristics are adjusted by bending the core. In the case of a butting core, the pressing force is adjusted and the balance is adjusted.

[0005]

The adjusting means for improving the residual characteristics in such a conventional split-type leakage current measuring device requires a lot of time for the adjustment.
Because the adjusting means requires skill, some adjusters may make excessive adjustments and deteriorate the characteristics, and in severe cases, change the characteristics of the magnetic material and do not return to the original state. In some cases, the result may be unexpected. An object of the present invention is to provide a split-type leakage current measuring device that solves such a problem.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a semi-annular pair of cores obtained by dividing an annular core into two parts, and a pair of cores wound near both ends thereof. The induced voltages are added to at least two coils for each core and two sets of coils facing each other across two divided surfaces when the end faces of the pair of cores are opposed to each other to form an annular shape. Polarity is connected in series to each other, and the induced voltages added by the series connection are respectively input and amplified, and a pair of amplifiers provided with gain adjusting means, and the outputs of the pair of amplifiers are input and the phases are respectively input. A pair of phase adjusters that are retarded, and include phase adjustment means,
This problem can be solved by providing an adder for adding both outputs of the pair of phase adjusters, and a display for displaying the output of the adder, and adjusting the residual current by adjusting each of the adjusting means.

Further, the above-mentioned problem is solved in the preceding paragraph, in that each of the adjusting means is a variable resistor.

[0008]

In the case where the end faces of a pair of cores are opposed to each other to form an annular shape, two sets of coils facing each other across two divided surfaces are output from terminals connected in series to polarities to which respective induced voltages are added. Since the two voltages are obtained by capturing the leakage magnetic flux caused by the residual current, the magnetic coupling state of the two core split surfaces is output as a voltage. A pair of amplifiers,
The phase adjuster amplifies both outputs and delays the phase. The degree of amplification and the degree of phase delay are adjusted by adjusting the variable resistors provided for each. By this adjustment, it is possible to obtain a state similar to a state where the magnetic coupling of two core split surfaces is balanced, and it is possible to reduce the residual current.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention. Reference numeral 10 denotes a core, which is composed of two parts of a pair of cores 10A and 10B that are annular when brought into contact with each other.
A coil A and a coil D are located near both ends of the core 10A, respectively.
On the other hand, coils B and C are respectively wound near both ends of the core 10B, and the coils A and B,
Coil C and coil D are both connected in series with a polarity that adds the induced voltage. As in the above-mentioned conventional example, a shield member for shielding each coil is provided, but illustration is omitted.

[0010] Reference numerals 1 and 3 denote amplifiers. The amplifier 1 receives an output of the coil A and the coil B connected in series, and the amplifier 3 has the coil C and the coil D connected in series. Output is input. VR ₁ and VR ₃ are variable resistors provided in the amplifiers 1 and 3, respectively, and adjust the gain of each amplifier.

Reference numerals 2 and 4 denote phase adjusters. The output P _{1 of the} amplifier 1 is input to the phase adjuster 2, while the output P _{3 of the} amplifier ₃ is input to the phase adjuster 4. VR
Reference numerals ₂ and VR ₄ denote variable resistors provided in the phase adjusters 2 and 4, respectively, and function as phase adjusting means of each phase adjuster.

Reference numeral 5 denotes an adder. The outputs of the two phase adjusters ₂ and ₄ , P ₂ and P _4, are input, and the two are vector-added and output as an output P ₅ . 6 is a meter display is inputted the output P ₅ of the adder 5.

The procedure for adjusting the apparatus according to the present invention will be described below. The split surfaces C ₁ and C ₂ of the core 10 are opened, the toroidal core 10 is bisected, and the electric wire to be measured (W in FIG. 1) is inserted and closed again. Primary current 1 to the wire
(A) is flowed, and the electric wire W is located at a position where the residual amount is usually maximum. The output P ₂ of the phase adjuster ₂ and the output P ₄ of the phase adjuster ₄ are observed with an oscilloscope (not shown), and the phase is adjusted by the variable resistors VR ₂ and VR ₄ so that the phase difference between them is eliminated. adjust.

When the phase difference becomes zero, the output P5 of the adder 5
Variable resistors V provided in the amplifiers 1 and 3 so that
Adjust the R ₁ and VR ₃ to moderate the gain of both amplifiers.

Thereafter, the primary current I _{1 is set} to zero, and only the zero-phase current flows, and the variable resistor VR ₅ of the adder ₅ is adjusted to a desired output value suitable for display on the display device 6.

In the above embodiment, two coils are wound on each core, each having a total of four coils. However, the number of coils may be increased depending on the situation.

Although the above adjustment is performed manually, it may be performed automatically by a computer.

[0018]

As described above, according to the present invention, it is possible to easily adjust the residual current, which cannot be handled after completion, because the performance is conventionally determined in the assembly process even after the product is completed. In other words, anyone can adjust the balance of the divided surface of the core, which was a special technology in the past. In particular, when the core is of the overlapping fitting type, it is possible to improve the point that the fitting state has to be taken into consideration so that the opening / closing operation of the core becomes difficult when trying to improve the residual current.

Further, since the adjustment can be automatically performed by using a computer, it is possible to improve the point that the characteristics are apt to change due to aging in the past, and it is possible to maintain the high performance state for a long time. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory front view of a conventional device.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

[Explanation of symbols]

Reference Signs List 1 amplifier 2 phase adjuster 3 amplifier 4 phase adjuster 5 adder 6 display 10 core 10A core 10B core A coil B coil C coil D coil C ₁ division surface C ₂ division surface VR ₁ variable resistor VR ₂ variable resistor VR ₃ variable resistor VR ₄ variable resistor VR ₅ variable resistor

Claims (2)

[Claims] 1. A pair of semi-annular cores obtained by dividing an annular core into two, at least two coils for at least each core wound near both ends of each of the pair of cores, The two sets of coils facing each other across the two divided surfaces in the case where the end faces of the core are opposed to each other to form an annular shape are connected in series to the polarity to which each induced voltage is added, and are added by the series connection. And a pair of amplifiers each provided with a gain adjustment unit, and a pair of phases each provided with an output of the pair of amplifiers to delay the phase and to include a phase adjustment unit. An adjuster; an adder for adding both outputs of the pair of phase adjusters; and a display for displaying the output of the adder, wherein the residual current is adjusted by adjusting the adjusting means. Minutes Split type leak current measuring device. 2. The split-type leakage current measuring device according to claim 1, wherein each of the adjusting means is a variable resistor.