JPH0337018Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a malfunction prevention circuit in a magnetic reversal display.

(Prior Art) A magnetic reversal display includes a stator around which a display drive coil is wound, the polarity of both ends of which is changed to the opposite polarity by excitation of the display drive coil, and a stator that rotates in reverse based on the change in polarity of the stator. It consists of a magnetized disk.

(Problem to be solved by the invention) However, when an external magnetic field penetrates the stator in the magnetic reversal display, the polarity of both ends of the stator changes based on the external magnetic field, resulting in a steady display state or an accident display. There is a risk that the status disk may rotate inverted and display incorrect information.

Structure of the invention (Means for solving the problem) This invention was made by paying attention to the above-mentioned problem, and the malfunction prevention circuit of the magnetic reversal display of this invention has a display drive coil wrapped around it. , a magnetic reversal display comprising a stator whose polarity at both ends is changed to the opposite polarity by excitation of a display driving coil, and a magnetized disk which rotates in reverse based on the change in polarity of the stator, On the other hand, it is wrapped with a protective coil that is short-circuited at both ends.

(Function) With the above configuration, when an external magnetic field penetrates the stator, a current flows through the short-circuited circuit of the protective coil due to electromagnetic induction, and as a result, a magnetic field in the opposite direction to the external magnetic field is induced. Therefore, the external magnetic field is weakened, thereby preventing display malfunctions caused by the external magnetic field.

(Example) An example in which this invention is embodied in a control circuit of a ground fault indicator H that indicates the passage of fault current in power cables and distribution equipment will be described below with reference to Figs. 1 to 3. .

A primary winding of a current transformer 2 is connected in series via terminals 3 and 4 to a grounding wire 1 of a power cable or distribution device. A full-wave rectifier 5 is connected to both terminals of the secondary winding of the current transformer 2 via a choke coil L. Note that Z is a surge absorber connected between both terminals on the secondary side of the current transformer 2. A display ID and a thyristor SCR as a switching element are connected in series to both the positive and negative terminals of the full-wave rectifier 5. This thyristor SCR has an anode connected to the display ID and a cathode connected to the negative terminal of the full-wave rectifier 5.

A capacitor C for charge storage is connected between the positive and negative terminals of the full-wave rectifier 5, as well as a capacitor discharge resistor R0, a Zener diode ZD as a thyristor temperature compensation element, and a gate voltage application resistor. A series circuit of a variable resistor R1 is connected.

The gate terminal of the thyristor SCR is connected to the positive terminal of the variable resistor R1.

The Zener diode ZD is designed not to conduct unless a Zener voltage or higher is applied, and the Zener voltage is applied to the thyristor.
The variable resistor R1 is set so that a sufficient gate voltage is applied to the gate terminal to turn on the SCR even when the temperature is low, and the variable resistor R1 is set so that the Zener diode ZD conducts and the gate voltage supplied to the thyristor SCR is required when the temperature is low. The resistance value is set to be equal to or higher than the gate trigger voltage.

To explain the display ID, this display ID
is a magnetic reversal display, with both ends having N and S poles.
A disc 6 magnetized as a pole is rotatably supported around a rotation shaft 7, and a round bar-shaped stator 8 has a magnetic pole part 8a corresponding to the S pole of the disc 6 and a magnetic pole part 8a corresponding to the N pole of the disc 6. It is formed to have a portion 8b. Note that the stator 8 is preferably formed of a material with low coercive force.

Between the magnetic pole portions 8a and 8b, there are magnetic pole portions 8a and 8b.
The display driving coil 9 connected between the positive terminal 10 and the negative terminal 11 of the display section ID is wound so that 8b is magnetized with the same polarity as the magnetic poles at both ends of the disk 6 in the state shown in FIG. There is. moreover,
A resistor R2 is connected to the positive terminal 10 of the display ID.
Both ends of the series circuit of the protective coil 12 are connected so as to be short-circuited, and the protective coil 12 is wound around the stator 8 in the same direction as the winding direction of the display driving coil 9.

Markers of different colors are displayed on the front side 6a and back side 6b of the disk 6 (in this embodiment, the front side 6a is black and the back side 6b is red).

Then, when a detection current flows through the coil 9,
As shown in FIG. 3, the magnetic pole part 8a is magnetized to the S pole, and the magnetic pole part 8b is magnetized to the N pole.
pole), and the disc 6
A label attached to the back surface 6b of the camera is designed to be displayed externally.

The indicator H of this embodiment initially shows that the mark on the surface 6a of the disk 6 faces outward, as shown in FIG. 2, to indicate a steady state.

The operation of the ground fault indicator H configured as above will be explained.

Now, the ground fault indicator H is attached to a utility pole or the like, and its terminals 3 and 4 are connected to a ground wire 1 provided on a power cable and power distribution equipment.

When a ground fault current flows through the grounding wire 1 due to deterioration of the power cable (not shown) in this installed state, a transformed current is output from the current transformer 2, and the transformed current is rectified by the full-wave rectifier 5. ,
Charge capacitor C.

When the capacitor C is charged and the voltage increases, and becomes higher than the Zener voltage of the Zener diode ZD, and the Zener diode ZD becomes conductive, the voltage across the variable resistor R1 is applied between the gate and cathode of the thyristor SCR.

When a sufficient gate voltage is applied to the thyristor SCR, the thyristor SCR turns on and becomes conductive. Then, the charged capacitor C is discharged and current flows to the display section ID.

When a current flows through the display driving coil 9 of the display unit ID, the magnetic pole part 8a is magnetized to the S pole and the magnetic pole part 8b is magnetized to the N pole, as shown in FIG. 8a (S pole), the magnetic pole part 8b (N pole) is reversely rotated so that the S pole faces the magnetic pole part 8b (N pole).
As a result, the mark attached to the back surface 6b of the disk 6 is displayed to the outside to indicate a ground fault accident.

By visually recognizing the mark on the back surface 6b, it can be determined that a ground fault has occurred in the grounding wire 1.

In addition, in the display section ID, since the protective coil 12 with both ends short-circuited is wound around the stator 8, even if the external magnetic field φ1 penetrates the stator 8 in the ground fault display state or steady display state,
An electromotive force is generated in the short-circuited series circuit of the protective coil 12 and the resistor R2 due to electromagnetic induction caused by the external magnetic field φ1, and a current I flows in the direction that blocks the external magnetic field φ1.
occurs, and as a result, a magnetic field φ2 in the opposite direction to the external magnetic field φ1 is induced, thereby weakening the external magnetic field φ1. As a result, disk 8
Prevents display malfunction due to external magnetic field φ1.

Note that this invention is not limited to the above-mentioned embodiments, and can be arbitrarily modified without departing from the spirit of this invention.

Effects of the invention As detailed above, this invention has the excellent effect of preventing the disk from malfunctioning even when an external magnetic field penetrates the stator, improving the reliability of display operation, and is an excellent invention for industrial use. .

[Brief explanation of drawings]

Fig. 1 is a control circuit diagram of a ground fault indicator according to an embodiment of this invention, Fig. 2 is a perspective view of the main parts of the display section, and Fig. 3 is a diagram showing the operation of the main parts of the display section. FIG. 1...Grounding wire, 2...Full wave rectifier, 5...Full wave rectifier, 6...Disk, 7...Rotation axis, 8...
Stator, 9... Display drive coil, 12... Protection coil, ID... Display section, SCR... Thyristor, R0, R1, R2... Resistor, C... Capacitor, ZD... Zener diode.

Claims (1)

[Claims for Utility Model Registration] A stator that is wound with a display drive coil and whose polarity at both ends is changed to the opposite polarity by excitation of the display drive coil, and a stator that rotates in reverse based on the change in the polarity of the stator. 1. A malfunction prevention circuit for a magnetic reversal display comprising a magnetized disk, characterized in that a protective coil having both ends short-circuited is wound around the stator.