JPH0543502U - Resistor for current detection - Google Patents

Abstract

(57) [Summary] [Structure] The resistance wires 1 and 2 are formed, for example, in a U shape, and are arranged so as to be parallel to each other. The conductors 3 and 4 are shaped so that the directions of currents flowing through the resistance wires 1 and 2 are opposite to each other. [Effect] It is difficult to generate an inductance peculiar to the current detection resistor, and is hardly affected by the change of the external magnetic field, and the generated thermoelectromotive force can be canceled.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a current detecting resistor used in a device such as an electronic load device.

[0002]

[Prior Art]

 It is a well-known method to insert a resistor into the circuit and measure the voltage drop of the resistor in order to obtain the value of the current flowing in the circuit. FIG. 7 shows the structure of such a conventional current detecting resistor. In FIG. 7, reference numeral 40 denotes a circuit board made of an insulator, and the ends of the resistance wires 41 and 42 are connected to conductors 43 and 44 provided on the circuit board 40 by soldering or the like.

The resistance wires 41 and 42 used for such a purpose are made of a material having a low temperature coefficient in order to enhance detection accuracy. The surface area is large so as to enhance the heat dissipation effect. By the way, when the currents i ₁ and i ₂ flow through the resistance wires 41 and 42 and the temperature of the resistance wires rises, a thermoelectromotive force is generated by the Seebeck effect at the ends of the resistance wires. The thermoelectromotive forces generated at both ends cancel each other out because they have the same magnitude and opposite directions when the temperatures at both ends of the resistance wire are equal. However, in an actual resistor, a difference in the resistance between the resistance wire and the conductor, a difference in the thermal resistance of the surroundings, etc., tends to cause a difference in the temperatures at both ends of the resistance wire. In that case, the magnitude of the thermoelectromotive force at both ends is different, and this difference in thermoelectromotive force causes an error in the detected current value.

Therefore, conventionally, as shown in FIG. 8, the resistance wires 51 and 52 are, for example, U-shaped so that the distance between the portion connected to the conductor 53 and the portion connected to the conductor 54 is reduced. The temperatures of both ends of the resistance wires 51 and 52 were made substantially equal.

[0005]

[Problems to be solved by the device]

However, in such a configuration, since the resistance wire is of a type close to the coil, the inductance inherent to the current detection resistor is generated due to the interlinkage magnetic flux due to the currents i ₁ and i ₂ . Therefore, if such a current detection resistor is used in an electronic load device, the applied voltage and the load current will be out of phase even if the AC voltage is supplied in the pure resistance load mode. And other inconveniences will occur. Furthermore, the configuration shown in FIG. 8 is easily affected by changes in the surrounding magnetic field caused by external devices such as a motor and a transformer.

An object of the present invention is to provide a current detecting resistor having a high electrical stability in which an inductance peculiar to the current detecting resistor is unlikely to occur and is hardly affected by a change in an external magnetic field. Especially.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention has a plurality of resistance wires arranged in parallel, and the direction of the current flowing through at least one resistance wire of the plurality of resistance wires depends on the direction of the current flowing through other resistance wires. And a conductor connecting the ends of the plurality of resistance wires so as to be opposite to the direction.

[0008]

[Action]

 According to the present invention, the direction of the current flowing through at least one resistance wire of the plurality of resistance wires arranged in parallel is opposite to the direction of the current flowing through the other resistance wires, and the number of resistances arranged in parallel All do not generate a magnetic field in the same direction, so the inductance inherent in resistors is unlikely to occur. In addition, even if the external magnetic field changes, the induced electromotive force caused by it changes the amount of current flowing in some resistance lines and decreases it. Is less than before.

[0009]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show the structure of an embodiment of the present invention. FIG. 1 is a perspective view and FIG. 2 is a plan view. The resistance lines 1 and 2 are formed in a U-shape having the same size so that the resistance values are the same, and are arranged in parallel so that the U-shapes overlap. Each end of the resistance wires 1 and 2 is connected to the conductors 3 and 4 by soldering or the like. Here, the connecting portions A, A ', B and B'of the resistance wire and the conductor are arranged so that the connecting portion A and the connecting portion B are close to each other and the connecting portion A'and the connecting portion B'are close to each other. is there. Further, the conductor 3 and the conductor 4 are coupled via an insulating material such as a thermal sheet having good heat conduction. As described above, in the case of this embodiment, the resistance wires 1 and 2 are U-shaped, but it is not necessary to limit the resistance wires to U-shaped, and various shapes such as a circular shape and a semicircular shape can be used. The same effect as the embodiment can be obtained.

FIG. 3 shows a circuit diagram of the present embodiment configured as described above. Figure 3 by clear from sea urchin, the resistance value of the entire resistor viewed from the input and output ends, the resistance value of the resistance wire 1 and the resistance value of the R ₁ resistance wire 2 when the R ₂ is R ₁ - the _{R 2 / R 1 + R 2} .

When the temperature of the resistance wires 1 and 2 rises in such a state, thermoelectromotive force is generated in the connection portions A, A ′, B and B ′. FIG. 4 shows an equivalent circuit diagram when the thermoelectromotive force generated at each of the connecting portions A, A ', B, B'is e ₁ , e ₁ ', e ₂ , e ₂ ', respectively. Here, the connecting portions A and B are provided close to each other, and the temperatures thereof are almost the same, so that e ₁ ≈e ₂ . Further, since the connecting portions A ′ and B ′ are also close to each other, e ₁ ′ ≈e ₂ ′. As described above, the following conditions are satisfied in this embodiment even when the temperature rises.

E ₁ ≈e ₂ e ₁ ′ ≈e ₂ ′ R ₁ = R ₂ FIG. 5 is a circuit diagram in which the circuit diagram of FIG. 4 is rewritten. In FIG. 5, the voltage between the input and output terminals is almost 0, and the resistance value of the entire resistor as viewed from the input and output terminals excluding e ₁ , e ₁ ′, e ₂ and e ₂ ′ is R ₁ · R ₂ / since R ₁ + is R _2, the Thevenin theorem, thermoelectric power _{e 1, e 1 ', e} 2, e 2' does not affect the load current flowing through the input and output terminals .

Further, the direction of the current i ₂ flowing through the current i ₁ and the resistance wire 2 through the resistance wire 1 in Figs. 1 and 2 are always to be the opposite, by the current i ₁ to the magnetic field and the current i ₂ The resulting magnetic fields cancel each other out. Therefore, the inductance peculiar to this detection resistor does not occur.

Furthermore, when the surrounding magnetic field changes, induced electromotive force is generated in the resistance line 1 and the resistance line 2 in the same direction. For example, when an induced current of Δi is generated in the resistance line 1 in the i ₁ direction, an induced current of Δi is also generated in the resistance line 2 in the i ₁ direction. Therefore, the current flowing through the resistance wires 1 and 2 is (i ₁ + Δi) + (i ₂ −Δi) = i ₁ + i ₂ , and the current flowing through the entire detection resistor is affected by the induced electromotive force. There is no.

In the embodiment described above, the detection resistor is composed of two resistance wires. However, for example, when the detection resistor is composed of three resistance wires, For this purpose, the detection resistor may be configured such that the direction of the current flowing through one of the resistance wires is opposite to the direction of the current flowing through the other two. Even with such a configuration, the inductance peculiar to the detection resistor is reduced as compared with the conventional example, and the influence of the external magnetic field is reduced. Here, even if the resistance value of one of the plurality of resistance wires is extremely close to 0, that is, even if this resistance wire is used as a so-called conductor, the above-described effect can be obtained.

FIG. 6 is a perspective view showing the configuration of another embodiment of the present invention. In this embodiment, the heat dissipation plates 5 and 6 are provided as heat sinks on the circuit board 40 near the connection between the conductors and both ends of the resistance wires 1 and 2. By providing the heat dissipation plates 5 and 6 as described above, the temperature of the connection portion between the resistance wire and the conductor can be lowered, and the thermal coupling between the end portions of the adjacent resistance wires can be further strengthened. Therefore, the magnitude of the thermoelectromotive force generated at both ends of the resistance wire is reduced, and the difference in the thermoelectromotive force generated at the adjacent connecting portion can be further reduced as compared with the case without the heat sink.

[0018]

[Effect of the device]

 As described above, according to the present invention, the inductance unique to the current detection resistor is unlikely to occur, is not easily affected by the change of the external magnetic field, and the generated thermoelectromotive force is suppressed. It is possible to cancel out, and it is possible to obtain a current detection resistor with high electrical stability.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention.

FIG. 2 is a plan view of the embodiment shown in FIG.

FIG. 3 is a circuit diagram of the embodiment shown in FIG.

FIG. 4 is a circuit diagram for explaining the operation of the embodiment shown in FIG.

5 is a circuit diagram for explaining the operation of the embodiment shown in FIG.

FIG. 6 is a perspective view showing the configuration of another embodiment of the present invention.

FIG. 7 is a perspective view showing an example of a configuration of a conventional current detecting resistor.

FIG. 8 is a perspective view showing another example of the configuration of a conventional current detecting resistor.

[Explanation of symbols]

 1, 2 Resistance wire 3, 4 Conductor 5, 6 Heat sink

Claims (3)

[Scope of utility model registration request] 1. A plurality of resistance wires arranged in parallel and a direction of a current flowing through at least one resistance wire of the plurality of resistance wires is opposite to a direction of a current flowing through other resistance wires. As described above, the current detecting resistor is provided with a conductor connecting the ends of the plurality of resistance wires. 2. A plurality of the resistance wires are arranged in parallel in a state where the resistance wires overlap each other, and a connection portion between each resistance wire and the conductor is adjacent to a connection portion between the resistance wire and the conductor. The resistor for current detection according to claim 1, wherein 3. The current detecting resistor according to claim 1, wherein a heat sink member is provided near the ends of the plurality of resistance wires.