JP3970401B2 - Current detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current detector used only for various industrial equipment, power equipment, electrical appliances, electronic equipment and the like.
[0002]
[Prior art]
AC motors such as DC motors, synchronous motors, and induction motors are widely used as power sources in industrial machines such as NC machine tools, robots, and electrical appliances such as air conditioners. These motors are controlled by servos and inverters, and a DC current detector that detects the DC current flowing through the motor is indispensable for high-precision and high-speed control. These current detectors must be electrically insulated from the primary side of the current to be measured and the secondary circuit section that generates an output proportional to the current to be measured. There is a method.
[0003]
The first is an insulation amplifier method that detects the current to be measured by passing it through a shunt resistor and insulating the voltage across it.
[0004]
The second is a magnetic proportional Hall CT that is detected by winding a coil around a core with a magnetic gap, converting the magnetic current generated in the magnetic gap into a voltage signal with a Hall sensor, and amplifying it with an amplifier circuit. method.
[0005]
The third one uses a core with a magnetic gap and a Hall sensor, similar to the second magnetic proportional Hall CT. However, the magnetic flux generated by the measured current of the primary coil is transferred to the secondary coil (current detection coil). The control loop including the Hall sensor operates so as to cancel the current flow. Since the magnetic flux in the magnetic gap is always 0, there is a magnetically balanced Hall CT that detects the current to be measured by measuring the secondary current that flows in proportion to the current of the primary coil.
[0006]
Each method has the following features. (1) The insulation amplifier method is highly accurate but expensive. (2) In the magnetic proportional Hall CT, since the voltage obtained by the Hall sensor is small, the amplifier amplifies the voltage to the required voltage, so that errors such as temperature drift of output and drift due to self-heating are large due to gain. However, it is the cheapest of the three methods. {Circle around (3)} The magnetically balanced Hall CT is small and highly accurate, but is more expensive than the magnetic proportional Hall CT.
[0007]
In recent years, servo drivers and inverter drivers have become smaller and more accurate and more functional, and current detectors used for them are also required to be smaller and more accurate. Demand is increasing.
[0008]
On the other hand, a demand of 20 kW or less is more demanded by motor capacity, so an on-board type current detector that directly solders the measurement current measurement terminal and the input / output signal terminal to the board is desired.
[0009]
FIG. 5 is a perspective view showing the structure of a conventional magnetically balanced hall CT. As shown in FIG. 5, conventionally, this type of hole CT has a core 51 formed by stacking punched metal magnetic plates, and a secondary coil 54 wound around a bobbin 53 is disposed on one side of the core 51. The primary coil 56 for passing the current to be measured is formed by passing the conducting wire through the inner diameter of the core for one turn or by winding it from above the housing case.
[0010]
[Problems to be solved by the invention]
However, in the Hall CT, in order for the sum of the magnetic flux Φ1 generated by the primary coil 56 and the magnetic flux Φ2 generated by the current flowing in the secondary coil 54 to cancel out this, it becomes 0 in the magnetic gap 57. When the primary coil 56, the secondary coil 54, and the magnetic gap 57 are formed apart from each other, it is necessary to increase the cross-sectional area of the core so that the core is not magnetically saturated with the magnetic flux generated by the primary coil 56 within the measurement current range. is there. For this reason, the number of laminated metal magnetic plates is increased and the price is increased. Further, in such CT, the primary coil 56 passes through one turn and the measurement current increases. There is a problem that the inner diameter of the core 51 becomes large because a thick conductor is penetrated, and it is difficult to reduce the size, and there is a problem that the primary winding cannot be made other than a harness.
[0011]
Accordingly, an object of the present invention is to provide a current detector comprising a magnetically balanced Hall CT that can detect a low current range, is small, and is inexpensive.
[0012]
Another technical problem 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 measurement current measurement terminal and an input / output terminal to a substrate. .
[0013]
[Means for Solving the Problems]
In order to solve the above technical problem, the current detector of the present invention includes a bobbin around which a coil is wound, a core made of a ferromagnetic material having a magnetic gap, and a circuit board on which a magnetosensitive element is mounted. In the current detector, a magnetic balance type in which a primary coil and a secondary coil are formed as the coil on the bobbin, and the bobbin is used for insulating and dividing the primary coil and the secondary coil. And having a partition, the primary coil and the secondary coil are provided adjacent to each other via the partition, and the core made of the ferromagnetic material is configured so that the magnetic gap is smaller than the height of the collar of the bobbin. It is characterized by substantially consisting of an integral body having a formed circular shape .
[0015]
In the present invention, in a current detector comprising a bobbin around which a coil is wound, a core made of a ferromagnetic material having a magnetic gap, and a circuit board on which a magnetosensitive element is mounted, the coil is placed on the bobbin as the coil. A magnetic balance type in which a primary coil and a secondary coil are formed, the primary coil is wound on the secondary coil, an insulating layer is provided on the secondary coil, The primary coil is wound around the core, and the core made of the ferromagnetic material is substantially composed of an integral body having a circular shape formed so that the magnetic gap is smaller than the height of the collar of the bobbin. It is a feature.
[0017]
In the present invention, in any one of the current detectors, either the primary coil or the secondary coil is made of a three-layer insulated wire.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0020]
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 is an explanatory view showing a state of a core before and after a bobbin is inserted. . As shown in FIG. 1, the current detector has a cylindrical bobbin 1 made of an insulating resin provided with a primary coil 11 for passing a current to be measured and a secondary coil 12 for canceling the magnetic field of the primary coil 11. They are provided adjacent to each other via the partition wall 13.
[0021]
As shown in FIG. 3, the core 2 made of a ferromagnetic material made of a metal magnetic plate is formed in advance so that the magnetic gap 4 can be passed through the flange 14 of the bobbin 1, and after inserting the bobbin 1, The outer portion 2a of the core 2 is bent, narrowed to a predetermined magnetic gap dimension Lg, and molded to form a U-shaped core 2.
[0022]
As shown in FIG. 2, the Hall sensor 3 and other circuit components are mounted, and the circuit board 5 having the input / output terminals 7 is provided on the bobbin 1 so that the Hall sensor 3 is located in the magnetic gap 4. It is fixed and held by the two storage locking portions 14a and 14b. The end of the secondary coil 12 is tangled with pins 8 a and 8 b provided on the bobbin 1, and the pins are connected to the circuit board 5. The current to be measured is supplied to the terminals 11a and 11b of the primary coil.
[0023]
As shown in FIG. 1, by arranging the primary coil 11, the secondary coil 12, and the magnetic gap 4 adjacent to each other, 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 are Since the primary coil 11 and the secondary coil 12 cancel each other, 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 to bend a single metal magnetic plate, and the core 2 can be made small and simple.
[0024]
FIG. 4 is a cross-sectional view showing a current detector according to another embodiment of the present invention. Referring to FIG. 4, in a current detector according to another embodiment, a secondary coil 22 is wound around a bobbin 23, an insulator 24 made of insulating tape or the like is formed, and the primary coil 21 is wound thereon. The current detector is different from the current detector according to the above-described embodiment in that the configuration is rotated. Since the magnetic flux is canceled between the primary and secondary coils 21 and 22 similarly to the current detector in the above-described 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, but three-layer insulation is provided for either one of the coils. Naturally, the same effect can be obtained even if the coil is disposed in the same manner as described above using a wire, an insulating film electric wire or the like.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a current detector including a magnetically balanced Hall CT that can detect a low current range, is small, and is inexpensive.
[0026]
Further, according to the present invention, it is possible to provide an on-board type current detector in which a primary coil is incorporated and a measurement terminal and an input / output terminal of a current to be measured can be directly soldered 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.
3 is a state explanatory diagram of a core before and after insertion of a bobbin 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 prior art.
[Explanation of symbols]
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 Bulkhead 14 鍔

Claims (3)

In a current detector comprising a bobbin around which a coil is wound, a core made of a ferromagnetic material having a magnetic gap, and a circuit board on which a magnetosensitive element is mounted, a primary coil and 2 as the coil on the bobbin The bobbin has a partition for insulatingly dividing the primary coil and the secondary coil, and the primary coil and the secondary coil are connected to the partition wall. The core made of the ferromagnetic material is substantially made of an integral body having a circular shape formed so that the magnetic gap is smaller than the height of the flange of the bobbin. Current detector. In a current detector including a bobbin around which a coil is wound, a core made of a ferromagnetic material having a magnetic gap, and a circuit board on which a magnetosensitive element is mounted, a primary coil and a secondary coil are provided as the coil on the bobbin. A magnetic balance type formed with a coil, wherein the primary coil is wound on the secondary coil, an insulating layer is provided on the secondary coil, and the primary coil is provided on the insulating layer. The current detector is characterized in that the wound and core made of the ferromagnetic material is substantially made of an integral body having a circular shape formed so that the magnetic gap is smaller than the height of the collar of the bobbin . . 3. The current detector according to claim 1, wherein either the primary coil or the secondary coil is made of a three-layer insulated wire.

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