JP3046008U - Clamp type leak current meter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a low-cost clamp-type leakage ammeter which can measure a low-frequency specific frequency current extremely easily and accurately, and which is excellent in workability. Aim. SOLUTION: A current detector 10 in which a current transformer 20 is accommodated in a clamp unit 11, and an input unit 2 electrically connected to the current transformer 20.
And a shunt resistor 21 for converting the current input by the current transformer 20 into a voltage, and amplifiers 22 and 50 for amplifying the voltage converted by the shunt resistor 21 to a normal I ₀ signal level.
H _Z and 60H _Z remove notch filter 23, the specific frequency filter 24, low pass filter 26, to constitute a I ₀ / Ig selector switch 4, A / D providing the converter 27 ammeter body 1 and a clamp-type leakage current meter .

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a clamp-type leakage ammeter.

[0002]

[Prior art]

 Conventionally, in order to search for an insulation failure in a field such as a cubicle, as shown in FIG. A long lead wire 32 for input was connected to the ammeter main body 34, and the clamp section 31 of the current detector 30 was inserted between target electric circuits to input an Ig current, and provided at the end of the lead wire 32. An alligator grip 33 or the like is connected to a power supply circuit, an in-phase component of an Ig current and a voltage is extracted as an Igr current, and an Igr-type insulation monitoring probe configured to display the current is used.

[0003]

[Problems to be solved by the invention]

 However, in the spacecraft constructed as described above, since the in-phase component of the Ig current and the voltage is displayed as the Igr current, a long lead wire 32 for inputting the voltage is required. Not only that, it is extremely troublesome to select a point for inputting a voltage in a field such as a cubicle and to connect the lead wire 32, and to detect the in-phase component between the Ig current and the voltage as the Ig r current. As a result, the internal circuit becomes complicated and large, so it cannot be provided at a low cost.In addition, the workability in fields such as cubicles and in narrow places is extremely poor. Had a problem that it could not be adapted.

The present invention has been made in view of the above-mentioned problems, and can measure a low-frequency specific frequency current extremely easily and accurately in a field such as a cubicle. An object of the present invention is to provide an inexpensive clamp-type leakage ammeter with excellent performance.

[0005]

[Means for Solving the Problems]

The present invention provides a current detector 10 having a clamp unit 11 accommodating a current transformer 20 which can be freely opened and closed, and an input unit 2 connected to the current transformer 20 and a current value display unit 3 having the following circuit. a shunt resistor 21 for converting a current input by the current transformer former 20 to a voltage, the amplifier 22 which amplifies the voltage converted by the shunt resistor 21 to the normal I ₀ signal levels, 50H _Z and 60H _Z remove notch filter 23, a specific frequency filter 24 that extracts a specific frequency current, constitutes a clamp-type leakage current meter and a low-pass filter 26, I ₀ / ammeter body 1 provided with the Ig changeover switch 4 and the a / D converter 27, This is a solution to the conventional problems.

In order to detect the I ₀ current, the I ₀ / Ig switch 4 is set to the I ₀ side, the clamp unit 11 provided in the current detector 10 is opened, and the current housed in the clamp unit 11 is opened. The transformer 20 is sandwiched between target electric circuits. The current detected by the current transformer 20 is converted to a voltage by the shunt resistor 21 and amplified by the amplifier 22 to a normal I ₀ signal level. This I ₀ current signal flows from the I ₀ / Ig changeover switch 4 to the A / D converter 27, where the current value is converted, and the current value is displayed on the current value display unit 3.

[0007] To detect the Ig current value, the I ₀ / Ig switch 4 is set to the Ig side. Detected current by mosquitoes rent transformers 20 is converted into a voltage by a shunt resistor 21, the amplifier 22 is amplified to a normal I ₀ signal levels, 50H _Z and 60H _Z by the notch filter 23 is removed, the specific frequency filter 24 A specific frequency current is extracted. The specific frequency current is converted to a circuit voltage conversion value (200 V) by the amplifier 25, passes through the low-pass filter 26, is converted to a current value by the A / D converter 27, and the value is displayed on the current value display section 3.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a first embodiment of the present invention, FIG. 2 is a front view showing a second embodiment of the present invention, and FIG. 3 is a block diagram showing an internal circuit.

1 and 2, 1 is an ammeter main body, 2 is an input section, 3 is a current value display section, 4 is an I ₀ / Ig switch, 5 is a power switch, and 6 is a current transformer switch. When the current transformer changeover switch 6 uses the current detector 10 having the large-diameter-adaptive clamp section 11, the current-transformer change-over switch 6 is inserted into the large-diameter side, and the small-diameter-compatible current detector having a different secondary output is used. When using 10 (see Fig. 2), switch to the smaller diameter side.

[0010] Reference numeral 10 denotes a current detector, and 11 denotes a clamp unit provided at the tip of the current detector 10 so as to be openable and closable. A current transformer 20, which will be described later, is housed inside the clamp unit 11. 12 is a clamp opening / closing lever, and 13 is a lead wire for electrically connecting the current detector 10 and the ammeter body 1.

In FIG. 3, reference numeral 20 denotes a current transformer. The current transformer 20 is housed in the clamp unit 11 of the current detector 10. Reference numeral 21 denotes a shunt resistor, and the shunt resistor 21 converts a current detected by the current transformer 20 into a voltage. Reference numeral 22 denotes an amplifier. The voltage converted by the shunt resistor 21 by the amplifier 22 is amplified to a normal _Io signal level. 2 3 the notch filter, the notch filter 23 is 50H _Z twin T filter 23 a, consists of a 60H _Z twin T filter 23b, 50H _Z and 60H _Z Ri by the notch filter 23 is removed. Reference numeral 24 denotes a specific frequency filter. The specific frequency filter 24 includes an oscillator 24a, a frequency divider 24b, and a switched capacitor filter 24c. The specific frequency filter 24 extracts a specific frequency current. Reference numeral 25 denotes an amplifier for converting a specific frequency current extracted by the specific frequency filter 24 into an electric circuit (200 V). 26 is a low-pass filter, which removes switching noise of the switched capacitor filter 24c. Reference numeral 27 denotes an A / D converter, which converts an analog quantity into a digital quantity by a double integration method.

In order to measure the I ₀ current in the field of a cubicle or the like using the clamp type leakage current meter of the present invention configured as described above, the power switch 5 is turned on and the I ₀ / Ig switch is set. 4 is placed on the _I0 side, the clamp unit 11 is opened by pressing the clamp opening / closing lever 12 provided on the current detector 10, and the current transformer 20 housed in the clamp unit 11 is sandwiched between the target electric circuits. The current detected by the rent transformer 20 is converted into a voltage by the shunt resistor 21 and amplified by the amplifier 22 to a normal I ₀ signal level. This I ₀ current signal is converted into a current value by the A / D converter 27, and its value is displayed on the current value display section 3.

Next, to measure the Ig current, the I ₀ / Ig switch 4 is switched to the Ig side, and the clamp opening / closing lever 12 provided on the current detector 10 is pushed to open the clamp section 11, and the clamp section 11 is opened. The current transformer 20 housed in 11 is sandwiched between target electric circuits. Current detected by the current transformer 20 is converted into a voltage by the shunt resistor 21 is amplified by the amplifier 22 to the I ₀ signal levels, 50H _Z and 60H _Z by the notch filter 23 is removed, the specific frequency by the specific frequency filter 24 The current is extracted. This current is converted to 200 V by the amplifier 25, passed through the low-pass filter 26, converted into a current value by the A / D converter 27, and the current value is displayed on the current value display unit 3.

Accordingly, the I ₀ / Ig selector switch 4 is set to the I ₀ side or the Ig side, and the clamp unit 11 provided on the current detector 10 is simply inserted into the target electric circuit. It is possible to accurately measure a specific low-frequency current at a specific frequency, and since the structure is simple, small, and lightweight, it is easy to handle, and workability in fields such as cubicles can be significantly improved.

[0015]

[Effect of the invention]

 According to the present invention, as described above, not only can a specific low-frequency current at a low frequency be measured extremely easily and accurately in a field such as a cubicle, but also because of its simple structure, light weight and small size, it can be handled easily. It has excellent advantages such as being easy and inexpensive.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of the present invention.

FIG. 2 is a front view showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing the internal wiring of the present invention.

FIG. 4 is a front view showing a conventional Ig r type insulation monitoring probe.

[Explanation of symbols]

1 ammeter body 2 input section 3 the current value display section 4 I ₀ / Ig selector switch 10 current detector 11 clamp part 20 current transformer 21 shunt resistor 22 amplifier 23 notch filter 24 specific frequency filter 25 amplifier 26 low-pass filter 27 A / D converter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location G01R 31/02 G01R 15/02 F H01F 38/28 H01F 40/06

Claims (1)

[Utility model registration claims] 1. A current detector (10) provided with a clamp unit (11) containing a current transformer (20) openably and closably, and an input unit (2) electrically connected to the current transformer (20). On the circuit of the current value display section (3),
A shunt resistor for converting the current input by a current transformer (20) to a voltage (21), an amplifier for amplifying the voltage converted by the shunt resistor (21) to the normal I ₀ signal level (22), 50H _Z and 60
H _Z for removing notch filter (23), the specific frequency filter for extracting a specific frequency current (24), a low-pass filter (26), I ₀ / Ig selector switch (4) and A / D
A clamp type leakage current comprising an ammeter main body (1) provided with a converter (27), and measuring the I ₀ current value and the Ig current value by switching the I ₀ / Ig switch (4). Total.