JPH11201999A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-board type current detector comprising an inexpensive small magnetic balance type Hall CT having a low current detection range and incorporating a primary coil in which current measuring terminals and I/O terminals can be bonded directly to a board. SOLUTION: The magnetic balance type current detector comprises a bobbin 1 applied with a coil, a core 2 of a ferromagnetic body having a magnetic gap 4, and a circuit board 5 mounting a Hall sensor 3 wherein the coil applied onto the bobbin 1 comprises primary and secondary coils 11, 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detector used only for various industrial equipment, power equipment, electric appliances, electronic equipment and the like.

[0002]

2. Description of the Related Art Industrial equipment such as NC machine tools and robots,
AC motors such as DC motors, synchronous motors, and induction motors are widely used as power sources for appliances such as air conditioners. These motors are controlled by a servo and an inverter, and a DC current detector for detecting a DC current flowing through the motor is indispensable for high-accuracy and high-speed control. In these current detectors, the primary side of the current to be measured and the secondary side circuit section that generates an output proportional to the current to be measured must be electrically insulated. There is a method.

One is an insulation amplifier system in which a current to be measured flows through a shunt resistor, and the voltage between both ends is insulated and detected.

[0004] Second, a core having a magnetic gap is
A magnetic proportional Hall CT system in which a coil is wound, a magnetic flux generated in a magnetic gap from a measured current is converted into a voltage signal by a Hall sensor, and the voltage signal is detected by amplification by an amplifier circuit.

The third is the second magnetic proportional Hall CT.
Similarly to the above, a control loop including a Hall sensor is used to cancel the magnetic flux generated by the measured current of the primary coil by passing a current through the secondary coil (current detection coil), using a core with a magnetic gap and a Hall sensor. Is what works. Since the magnetic flux in the magnetic gap is always 0,
There is a magnetically balanced Hall CT that detects a measured current by measuring a secondary current that flows in proportion to the current of the primary coil.

Each system has the following features. The insulated amplifier method must be highly accurate but expensive.
In the magnetic proportional Hall CT, since the voltage obtained by the Hall sensor is small, it is amplified to the required voltage, so that errors such as temperature drift of the output and drift due to self-heating are large depending on the gain. However, it is the cheapest among the three methods. The magnetically balanced Hall CT has a small error and high accuracy, but is more expensive than the magnetic proportional Hall CT.

In recent years, miniaturization, high accuracy, and high functionality of servo drivers and inverter drivers have been remarkably demanded, and the current detectors used therein have also been required to be small and high accuracy. The demand for Hall CT is increasing.

[0008] In addition, since a low current of 20 kW or less is much more demanded according to the motor capacity, an on-board type current detector which directly solders a measuring terminal of a measured current and an input / output signal terminal to a substrate is desired. ing.

FIG. 5 is a perspective view showing the structure of a conventional magnetically balanced Hall CT. As shown in FIG. 5, a conventional hole CT of this type has a core 51 formed by laminating stamped and formed metal magnetic plates, and a secondary coil 54 wound around a bobbin 53.
Is disposed on one side of the core 51, and the primary coil 56 through which the current to be measured flows is formed by passing a conducting wire through the inner diameter of the core for one turn or by winding it over the housing case.

[0010]

However, in the above-mentioned Hall CT, the sum of the magnetic flux Φ1 generated by the primary coil 56 and the magnetic flux Φ2 generated by the current flowing through the secondary coil 54 is canceled in the magnetic gap 57 so as to cancel this. In order to reach 0, if the primary coil 56 and the secondary coil 54 and the magnetic gap 57 are formed apart from each other, the core is not magnetically saturated by the magnetic flux generated by the primary coil 56 within the range of the measured current. It is necessary to increase the cross-sectional area of the core. For this reason, the number of laminated metal magnetic plates increases and the price is high. Also, in such a CT, the measurement current becomes high when the primary coil 56 passes through one turn. There is a problem that the inner diameter of the core 51 becomes large because it penetrates a thick conducting wire, and it is difficult to make the core 51 small.

It is an object of the present invention to provide a small and inexpensive current detector comprising a magnetically balanced Hall CT which can detect a low current range.

Another technical object of the present invention is to provide an on-board type current detector having a built-in primary coil and capable of directly soldering a measuring terminal and an input / output terminal of a current to be measured to a substrate. It is in.

[0013]

In order to solve the above-mentioned technical problems, a current detector according to the present invention comprises a bobbin wound with a coil, a core made of a ferromagnetic material having a magnetic gap, and a magneto-sensitive element. And a circuit board on which a primary coil and a secondary coil are formed as the coils on the bobbin.

Further, in the present invention, in the current detector, the bobbin has a partition wall for insulatingly dividing the primary coil and the secondary coil.

Further, in the present invention, in the current detector, the primary coil is wound on the secondary coil.

According to the present invention, in the current detector, an insulating layer is provided on the secondary coil, and the primary coil is wound on the insulating layer.

Further, according to the present invention, in any one of the current detectors described above, one of the primary coil and the secondary coil is formed of a three-layer insulated wire.

Further, according to the present invention, in any one of the current detectors described above, the core made of the ferromagnetic material has an integral shape having a circular shape formed so that the magnetic gap is smaller than the height of the collar of the bobbin. It is characterized by being substantially composed of objects.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 to 3 show a current detector according to an embodiment of the present invention. FIG. 1 is a top sectional view, FIG. 2 is a front view, and FIG. 3 shows a state of a core before and after bobbin insertion. FIG. As shown in FIG. 1, a current detector is provided on a cylindrical bobbin 1 made of an insulating resin, with a primary coil 11 for flowing a current to be measured and a secondary coil 11 for canceling a magnetic field of the primary coil 11.
The next coil 12 is provided adjacently with a partition 13 interposed therebetween.

As shown in FIG. 3, the core 2 made of a ferromagnetic material made of a metal magnetic plate is previously formed by opening the magnetic gap 4 so that the flange 14 of the bobbin 1 can pass therethrough. After the insertion, the outer portion 2a of the core 2 is bent, narrowed to a predetermined magnetic gap dimension Lg, and formed to form a U-shaped core 2.

As shown in FIG. 2, a circuit board 5 on which the Hall sensor 3 and other circuit components are mounted and the input / output terminals 7 are provided.
In other words, the hall sensor 3 is provided with two storage locking portions 14 provided on the bobbin 1 so as to be located in the magnetic gap 4.
a, 14b fixedly held. The terminal of the secondary coil 12 is wrapped around pins 8a and 8b provided on the bobbin 1,
The pins are connected to the circuit board 5. The measured current is
The terminals 11a and 11b of the primary coil are energized.

As shown in FIG. 1, the magnetic flux Φ1 generated by the primary coil 11 and the magnetic flux Φ2 generated by the current flowing through the secondary coil 12 by arranging the primary coil 11 and the secondary coil 12 and the magnetic gap 4 adjacent to each other. Is offset between the primary coil 11 and the secondary coil 12 in the bobbin 1, so that the magnetic flux leaking to the core 2 is reduced, and the cross-sectional area of the core 2 can be reduced. Therefore, it is sufficient for the core 2 only to bend a single metal magnetic plate, and the core 2 can be made small and simple.

FIG. 4 is a sectional view showing a current detector according to another embodiment of the present invention. Referring to FIG. 4, a current detector according to another embodiment includes a bobbin 23 wound with a secondary coil 22 and an insulator 24 made of an insulating tape or the like.
Is different from the current detector according to the above-described embodiment in that a primary coil 21 is wound therefrom. Since the magnetic flux is canceled between the primary and secondary coils 21 and 22 similarly to the current detector in the above embodiment, the same effect can be obtained. In the above embodiment of the present invention, the insulation between the primary coil 11 or 21 and the secondary coil 12 or 22 is ensured by the flange 13 or the insulator 24. It is natural that the same effect can be obtained even if the coil is arranged in the same manner as described above using a wire, an insulating film electric wire or the like.

[0025]

As described above, according to the present invention,
It is possible to provide a small-sized and inexpensive current detector including a magnetically balanced Hall CT, which can detect a low current range.

Further, according to the present invention, it is possible to provide an on-board type current detector having a built-in primary coil and capable of directly soldering a measuring terminal and an input / output terminal of a current to be measured to a substrate.

[Brief description of the drawings]

FIG. 1 is a top sectional view showing a current detector according to an embodiment of the present invention.

FIG. 2 is a front view of the current detector of FIG.

FIG. 3 is an explanatory diagram of a state of a core before and after bobbin insertion of the current detector of FIG. 1;

FIG. 4 is a top sectional view showing a current detector according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a magnetically balanced Hall CT according to the related art.

[Description of Signs] 1,53 bobbin 2,51 core 3,52 Hall sensor 5,55 circuit board 11,21,56 primary coil 12,22,54 secondary coil 13 partition wall 14 flange

Claims (6)

[Claims] 1. A current detector comprising a bobbin on which a coil is wound, a core made of a ferromagnetic material having a magnetic gap, and a circuit board on which a magneto-sensitive element is mounted. A current detector characterized in that it is of a magnetic balance type in which a secondary coil and a secondary coil are formed. 2. The current detector according to claim 1, wherein the bobbin has a partition for insulatingly dividing the primary coil and the secondary coil. 3. The current detector according to claim 1, wherein said primary coil is wound on said secondary coil. 4. The current detector according to claim 3, wherein an insulating layer is provided on the secondary coil, and the primary coil is wound on the insulating layer. vessel. 5. The current detector according to claim 1, wherein one of said primary coil and said secondary coil comprises a three-layer insulated wire. Current detector. 6. The current detector according to claim 1, wherein the core made of the ferromagnetic material has a magnetic gap formed to be smaller than a height of a flange of the bobbin. A current detector substantially consisting of an integral body having a peripheral shape.