JPH04116909A - Transition current detection device - Google Patents

Abstract

PURPOSE:To obtain induction current for tracking transition current by retaining one part of an electric wire in parallel with a conductor adjacently with a screening material which is mounted to the conductor and then providing the electric wire at an outer periphery of the screening material. CONSTITUTION:When transition current is allowed to flow to a conductor 5, a magnetic field F is generated at its periphery and an electric wire 8 is retained in parallel with the conductor 5 and adjacently, thus allowing induction current to flow to the electric wire 8. Influence of the magnetic field F which the electric wire 8 receives (influence of the magnetic field F in the electric wire 8 at areas other than a part which is in parallel with the conductor 5 and is retained at an adjacent state is reduced by screening effect of a screening material 7 and is ignored) is proportional to a length l of the electric wire and is inversely proportional to a distance r so that transition current can be detected always with a constant accuracy by fixing the length l of the electric wire and the distance r. The detection circuit is only the electric wire 8, inductance becomes extremely small, and an induction current (detection current) 12 can be obtained tracking the transition current 11 rapidly.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to, for example, I
G B T (Insulated Gate Bi)
The present invention relates to a transient current detection device that detects a transient current that occurs when a short circuit occurs in a polar transistor (PolarTransistor).

[Conventional technology]

FIG. 3 is a perspective view showing a conventional transient current detection device, and FIG. 4 is a configuration diagram showing one arm of an inverter device using a general IGBT.
T, 3 is the IGBT drive circuit, 4 is a measuring current transformer (hereinafter referred to as CT) that detects the current flowing through the conductor 5, 6 is an electrolytic capacitor, and F is the magnetic field generated by the transient current flowing through the conductor 5. be.

Next, the operation will be explained.

If IGBTs 1 and 2 become conductive at the same time for some reason, the condition is the same as a short circuit in the electrolytic capacitor 6, so an extremely large transient current flows through the conductor 5.

The conventional transient current detection device detects a transient current by using the CT 4 to obtain an induced current due to the magnetic field F generated by the transient current. In this case, the induced current is sent to the IGBT drive circuit 3, If the induced current value in the drive circuit 3 is equal to or higher than the set value, it is determined that a short circuit has occurred in IGET I, 2, and an OFF signal is output to IGBTI, 2 to cut off the current.

[Problem to be solved by the invention]

Conventional transient current detection devices are configured as described above, and the CT detects the transient current flowing through the conductor. However, since the CT is made up of a coil wound many times, the inductance increases and the current suddenly increases. For example, IC;
There were problems such as damage to the T.

This invention was made in order to solve the above-mentioned problems, and aims to provide a small and inexpensive transient current detection device that can reliably follow sudden changes in current and accurately detect transient current. purpose.

[Means for Solving the Problems] A transient current detection device according to the present invention includes a shielding material whose at least one end is attached to a conductor and which surrounds a part of the conductor along the direction of the electric path, and a shielding material that is attached to the conductor at least one end thereof. A part of the shielding material is passed through a hole near the attachment point to the conductor, and is kept parallel to and close to the conductor along the direction of the electrical path. It is equipped with an electric wire through which an induced current flows due to changes in the magnetic field caused by the current.

[For production]

In the transient current detection device according to the present invention, a part of the electric wire is maintained parallel to and close to the conductor by the shielding material attached to the conductor, and the electric wire is attached to the outer periphery of the shielding material. Due to the shielding effect of the shielding material, the magnetic field generated by the transient current will not strongly affect the electric wire other than the part that is kept parallel and close to the conductor. The portion of the wire that is held in this state is strongly influenced by the magnetic field, and an induced current is generated as the magnetic field changes.

(Example) Hereinafter, an example of the present invention will be explained with reference to the drawings.
The figure is a perspective view showing a transient current detection device according to an embodiment of the present invention. In the figure, the same reference numerals as those in the conventional device indicate the same or corresponding parts, so the explanation will be omitted. 7 is a shielding material (for example, a maecarta board) that is attached to the conductor 5 at both ends and surrounds a part of the conductor 5 along the direction of the electric path.
, 8 are passed through the holes 7a and 7b that the shielding material 7 has near the attachment point to the conductor 5, and a part thereof is maintained parallel to and close to the conductor 5 along the direction of the electric path, and the shielding material 7 is An electric wire attached to the outer periphery of the conductor 5 that carries an induced current due to a change in the magnetic field F caused by a transient current flowing through the conductor 5. i is the part where the electric wire 8 is maintained parallel to and close to the conductor 5 The wire length r is the distance from the wire 8 to the conductor 5.

Next, the operation will be explained.

If a transient current 11 as shown in Fig. 2(a) flows through the conductor 5, a magnetic field F will be generated around the conductor 5 according to the right-hand screw rule.
places an order. Therefore, when the electric wire 11A8 is held parallel to and close to the conductor 5, an induced current flows through the electric wire 8 due to a change in the magnetic field F. Here, the influence of the magnetic field F on @1IA8 (the influence of the magnetic field F on the wire 8 other than the part that is kept parallel and close to the conductor 5 is reduced by the shielding effect of the shielding material 7 and can be ignored) ) is proportional to the wire length l and inversely proportional to the distance Hr, so by making the shielding material a certain size and fixing the wire length l and distance r, it is possible to always detect transient currents with a constant accuracy. I can do it.

In addition, the transient current detection device according to the present invention is provided with an IT wire in place of the CT4 used in the conventional device, and since the detection circuit is only the tii8, the inductance is extremely small, and the transient current 11 An induced current (detected current) 12 as shown in FIG. 2(b) can be obtained by rapidly following the current.

In the above embodiment, the electric wire 8 was simply attached to the outer periphery of the shielding material 7, but the attached portion of the electric wire 8
If it is completely surrounded by the shielding material 7 (for example, another layer of shielding material is layered on top of the electric wire 8 attached to the outer periphery of the shielding material 7 during the above-mentioned survey), the shielding effect will be further improved. Therefore, it goes without saying that the accuracy is improved.

Further, in the above embodiment, a case has been described in which a transient current of IGBTI, 2 is detected, but any detection of a transient current may be used, and the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, a part of the electric wire is maintained parallel to and close to the conductor by the shielding material attached to the conductor, and the electric wire is attached to the outer periphery of the shielding material. Since the circuit for detecting transient currents consists of only electric wires and the inductance is extremely small, induced currents (
Detection current), and in other parts of the wire that are kept parallel and close to the conductor, the magnetic field is shielded by the shielding material, so the wire is kept parallel and close to the conductor. If the shielding material is manufactured so that the part of the wire that is maintained in a constant state is constant, transient current can be detected with constant accuracy, and the device can be made smaller and cheaper.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a transient current detection device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing a general transient current and induced current, and Fig. 3 is a perspective view showing a conventional transient current detection device. 4 are configuration diagrams showing one arm of an inverter device using a general IGBT. 5 is a conductor, 7 is a shielding material, 7a and 7b are holes provided in the shielding material, and 8 is an electric wire. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A transient current detection device that detects a transient current flowing in a conductor that is an electric path includes a shielding material that has at least one end attached to the conductor and surrounds a part of the conductor along the direction of the electric path, and the shielding material is connected to the conductor. The transient current flowing through the conductor is passed through a hole near the attachment point of the shielding material, and a part of the shielding material is kept parallel to and close to the conductor along the direction of the electrical path, and is attached to the outer periphery of the shielding material. What is claimed is: 1. A transient current detection device comprising: an electric wire through which an induced current flows due to a change in a magnetic field generated by the change in the magnetic field.