JPH04331380A - Ground detector - Google Patents

Abstract

PURPOSE:To detect the disconnection of a grounding conductor for performing electric shielding of a device or components in regard to electrical and electronic machinary and apparatus. CONSTITUTION:A grounding conductor is connected to a terminal of a third coil N3 of a ground detection transformer and both the terminals of the coil are grounded together. The detector is constituted so that the transformer may be excited by a first coil N1 and its signal may be monitored by a second coil N2. In the case where both the terminals of the third coil N3 are grounded, the output of the second coil is a low level, but, in the case where one terminal or both the terminals of the third coil N3 are broken, a high level signal is obtained in the second coil. The disconnection of a grounding conductor can be noticed by monitoring the output level of the second coil.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a break in a grounding wire.

0002

2. Description of the Related Art Conventionally, when a case, a power supply line, a shield, etc. are grounded, there is no way to know if the grounding line has become disconnected. In other words, normally no voltage is applied between the terminal to be grounded and the ground, and no current flows through the grounding wire, so it is not known whether the grounding wire is truly grounded or not. I was in a situation.

0003

[Means for Solving the Problems] Accordingly, in the present invention, the two secondary terminals of the transformer are both grounded, and the terminal to be grounded is connected to the secondary winding. The configuration is such that the short-circuit condition on the secondary side is monitored.

0004

[Operation] As a result, the terminal to be grounded is grounded in a double system by the secondary side terminal of the transformer, and by monitoring the short-circuit state of the secondary side of the transformer, one side of the double system is in an ungrounded state. It is possible to report this only if it becomes.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be explained below with reference to FIG. FIG. 1 is a block diagram of a grounding detection device for a shield earth of a transformer T1 having windings Na and Nb and having a shield terminal E between the windings. In Figure 1, T2 is a grounding detection transformer (magnetic core), N1, N2, N3
is the winding wound around the transformer T2, and SG is the winding wound around the transformer T2.
LV is a level detector (for example, a Schmitt circuit) that tests the level of the signal generated in the winding N2, and the two terminals of the winding N3 are both grounded at a and b, and the two terminals of the transformer T1 are grounded. It is connected to the output terminal E of the shield between the next and secondary windings.

Next, the operation of the grounding detection device shown in FIG. 1 will be explained. If both terminals a and b of winding N3 are sufficiently grounded, both ends of winding N3 of transformer T2 are in a short-circuit condition, and the signal transmission from winding N1 to winding N2 is reduced, and this Therefore, the output signal of the level detector LV is not generated. However, if one or both of the grounds of winding N3 are disconnected and become ungrounded, winding N1 to winding N2
The signal transmission to the level detector LV increases to generate an output signal at the level detector LV. (In addition, shield terminal E of transformer T1 and transformer T
If there is a concern that the winding N3 of No. 2 may be disconnected, terminal b may be changed to terminal b' as shown by the dotted line in FIG. 1).

FIG. 2 shows a modification of the ground detection device shown in FIG. Windings N1 and N2 in Figure 1 are common windings in Figure 2, and if the terminals of winding N3 are short-circuited due to grounding, a high level output signal from signal generator SG will be generated at resistor R. However, if the terminals of the winding N3 are opened, a low level signal is generated across the resistor R. LV is a level detector for level checking the voltage between the terminals of this resistor R.

As described above, according to the present invention, it is possible to carry out grounding in a dual system, and even when one of the grounding systems becomes non-grounding, this can be reported.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the configuration of an embodiment of the invention, and FIG. 2 is a block diagram for explaining another embodiment of the invention.

[Explanation of symbols]

Claims (1)

[Claims] 1. A magnetic core excitation signal generator, a first winding excited by the excitation signal generator, and a second winding for extracting an excitation signal of the first winding. a magnetic core having a third winding connected to a ground wire and having two terminals grounded;
and a level detector for verifying the level of the output signal of the second winding.