JP4852371B2 - Leakage current measuring device and measuring method - Google Patents

Description

  The present invention not only removes high-order harmonic components in particular, but also reliably removes or reduces low-order harmonic components to more accurately and quickly measure the leakage current of electrical equipment. And a measuring method.

  Leakage current occurs due to the insulation deterioration of the circuit, and also when the capacitor component is interposed in the circuit as a filter or the like regardless of the insulation deterioration May flow out of electrical circuit. In order to measure this leakage current, there is a method of installing a clamp meter or the like at a predetermined position on the electric circuit in a live line state.

  Leakage current due to insulation deterioration usually shows the same commercial frequency (fundamental frequency) as the circuit voltage, but when this is actually measured using a clamp meter etc., the current of the harmonic component due to the influence of disturbance Is superposed on the current of the fundamental wave component and shows a value larger than the current value of the fundamental wave component. “Harmonic component” is defined as a component other than the fundamental component in each component of the periodic composite wave, and generally has a frequency that is an integral multiple of the fundamental frequency of the fundamental component. However, in the present specification, the term “harmonic component” is hereinafter referred to as “unspecified noise that does not have such a constant frequency in the leakage current”. Used in the meaning of including.

  For example, FIG. 5 shows a leakage current waveform (a) and harmonics of a normal electrical installation and FIG. 6 shows a lighting device (fluorescent lamp) equipped with a general copper-iron type ballast. It is a figure which shows an example of the actual value of a wave component content rate ((b) in each figure). In the graph of the harmonic component content rate in each figure (b), the horizontal axis indicates the order of the harmonic component, the vertical axis indicates the content rate of each component, and the fundamental wave component is indicated by the order 1. . From each of these figures (a), the waveforms of these leakage currents are substantially the same as the commercial frequency, and from each of these figures (b), the waveforms of these leakage currents have the primary fundamental wave component. In addition, it can be seen that the harmonic components from the second order to the 40th order, which is the upper limit of the measurement range, are contained in a wide range though a trace amount. Regarding the relationship between the current value of the fundamental wave component and the display value of the clamp meter, the former is 3.67 mA in the example of FIG. 5, while the latter is 3.96 mA, and the example of FIG. Then, while the former is 0.024 mA, the latter is 0.030 mA, and the clamp meter display value of the latter is larger in any case.

  For this reason, a clamp meter or the like is usually equipped with a filter function adjusted so as to remove higher-order harmonic components (mainly higher than the fifth-order harmonic component). The display value when the filter function of the conventional clamp meter is validated is 3.70 mA in the example of FIG. 5, and 0.025 mA in the example of FIG.

There has also been proposed a leakage ammeter that connects the filters in multiple stages and connects them to measure a specific frequency current value at a low frequency (see Patent Documents 1 and 2).
Utility Model Registration No. 3046007 Utility Model Registration No. 3046008 Japanese Patent No. 3545886

  However, the present inventors have investigated the actual state of the leakage current flowing out from the electric device. In an electric device equipped with a high-frequency output type inverter circuit such as an inverter type fluorescent lamp, it is detected on the D-type ground line. The leakage current shows a very large value, and the measured value cannot be lowered by the filter function that can remove higher-order harmonic components built in the clamp meter that has been used in the past. It was discovered that the current cannot be measured. As a result of investigating this phenomenon, the leakage current flowing out of these electrical devices contains high-order harmonic components that can be removed by the filter function of conventional clamp meters. It was newly found that low-order harmonic components such as second-order and third-order components that are difficult to remove are contained in large quantities, and these low-order harmonic components prevent accurate measurement of leakage current.

  Therefore, the present invention reliably removes low-order even-order harmonic components in leakage current flowing out from an electric device or the like equipped with a high-frequency output type inverter circuit such as the inverter type fluorescent lamp as described above. An object of the present invention is to provide a leakage current measuring device and a measuring method capable of reducing odd harmonic components and measuring the leakage current of these electric devices more accurately and quickly.

As a result of intensive studies to solve the above-mentioned new problem, the present inventors have obtained a composite wave composed of a fundamental wave component and a harmonic component, for example, into a waveform corresponding to one cycle of the fundamental wave component. when attention is paid, the in the waveform, since the harmonic components even number is a positive half wave and negative half wave is equal present, positive or negative by integrating the expression for the instantaneous value of the composite wave half period as the integration interval the waveform (integrated value) is canceled, the integration result may be a 0, it was or
Odd harmonic components are also by integrating the instantaneous values of the composite wave half period as the integration interval, the half-wave and the negative half-wave of the same number of positive is canceled, integrates the positive or negative half-wave remains Therefore, the integration result can be reduced, and as a result, the odd harmonic components can be reduced.
In particular , the following calculation processing can be performed to remove or reduce particularly low-order harmonic components more efficiently . As a result, the true effective value of leakage current can be obtained more accurately. As a result, the present invention has been completed.

That is, in order to achieve the above object, the leakage current measuring apparatus of the present invention has a leakage current detection means for detecting a leakage current signal including a fundamental wave component and a harmonic component of an electric circuit, and the leakage current signal. A conversion circuit for converting to a voltage signal, an amplification circuit for amplifying the voltage signal, a filter circuit for removing high-order harmonic components in the output signal from the amplification circuit, an arithmetic circuit, and an arithmetic operation of the arithmetic circuit result comprising at least a display and / or a display-output circuit for outputting the arithmetic circuit, an output waveform of the filter circuit is input thereto, a phase angle with respect to the output waveform 90 ° × (2m- 1) N cycles of the fundamental component (N is an integer of 1 or more) each of two waveforms, a waveform shifted by (m is an integer of 1 or more) or a waveform whose period is shifted by π / 2ω from the output waveform. In Those that were separated extract, integration for each waveform, while integrating the half period of the fundamental wave component as the integration interval, the next half cycle of the expression of the instantaneous value by sign inversion following the half cycle of the each waveform After performing at least one integration operation to integrate as an interval, add these integration results for each of the two waveforms , calculate the square root of the sum of the squares of the two addition results, and calculate the effective value of the leakage current. It is characterized by being comprised so that it may obtain | require.

The leakage current measuring method of the present invention includes a step of attaching a leakage current detection means to an electric circuit, thereby detecting a leakage current signal composed of a fundamental wave component and a harmonic component, and converting the leakage current signal into a voltage signal. A conversion step for converting and outputting, an amplification step for amplifying the voltage signal, a filter step for removing high-order harmonic components in the output signal from the amplification circuit, an arithmetic processing step, and the arithmetic processing step At least a display / output step for displaying and / or outputting the calculation result in the calculation processing step , wherein the calculation processing step inputs an output waveform of the filter step inputted thereto and a phase angle of 90 ° × with respect to the output waveform (2m-1) (m is an integer of 1 or more) shifted by waveform or N cycles (N of each of the fundamental wave component of the two waveforms of a waveform cycle from the output waveform is shifted by [pi / 2 [omega is Were separated extracted corresponding to an integer greater than one), for each of the waveforms, as well as integrating the half period of the fundamental wave component as an integration section, the expression of the instantaneous value of the each waveform by negative reversed following the half cycle following the half cycle an integration calculation for integrating after conducting at least once each as an integration section, these integration results are added for each of the two waveforms, and calculates the square root of the sum of squares of the two addition results It is characterized in that an effective value of leakage current is obtained.

  According to the leakage current measuring apparatus and measuring method of the present invention, a waveform corresponding to N cycles of the fundamental wave component is extracted from a waveform signal input thereto in an arithmetic circuit, and this is sequentially integrated every half cycle. Therefore, it is possible to remove low-order even harmonic components close to the frequency of the fundamental component, which is difficult to remove completely with a conventional filter circuit, and to reduce odd harmonic components. it can.

Further, in the arithmetic circuit, the phase angle of the output signal from the filter circuit input thereto is shifted by 90 ° × (2m−1) (m is an integer of 1 or more) with respect to the waveform of the output signal. for the (the N 1 or more integer) N cycles of the fundamental wave component of the two waveforms of the waveform or waveform cycle from the waveform of the output signal is shifted by [pi / 2 [omega were separated extracted corresponding to each of the waveform with integrating the half period of the fundamental wave component as the integration interval, each at least one integral operation using the product minute next half cycle the expression of the instantaneous value by sign inversion followed the half-period of each of the waveform as the integration interval after performing times, these integration results are added for each waveform, by calculating the square root of the sum of squares of the addition result, frequency of complete difficult fundamental wave component can be removed by conventional filter circuit Close to the removal of the low-order of the even harmonics, reduce odd harmonic components is achieved, it is possible to obtain the effective value of accurately and quickly leakage current.

  Hereinafter, the leakage current measuring apparatus and measuring method of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of an embodiment of a leakage current measuring apparatus of the present invention. In the figure, (a) shows a mode in which signal arithmetic processing is performed in analog in the arithmetic circuit, and (b) shows a mode in which signal arithmetic processing is performed digitally in the arithmetic circuit. The same reference numerals are used for the respective parts. In this figure, the leakage current measuring apparatus 1 includes a clamp-type current transformer 2, a conversion circuit 3, an amplification circuit 4, a filter circuit 5, an AD converter circuit 7, an arithmetic circuit 6, and a display / output circuit 8.

  The clamp type current transformer 2 is installed in an electric circuit (not shown) and detects a leakage current flowing through the electric circuit. Such a clamp type current transformer 2 is not particularly limited, and a known one can be used.

  The conversion circuit 3 is provided to convert the leakage current signal output from the clamp type current transformer 2 into a voltage signal. As the conversion circuit 3, a shunt resistor or the like is usually used. This shunt resistor is connected in series to the secondary output line of the clamp type current transformer 2, and takes out a voltage signal from both ends of the resistor.

  The amplifier circuit 4 is provided to amplify the voltage signal output from the conversion circuit 3 to a signal level that can be arithmetically processed in an arithmetic circuit described later. As the amplifier circuit 4, a known transistor, operational amplifier, or the like can be used.

  The filter circuit 5 is used for attenuating low-order harmonic components other than the fundamental component and removing high-order harmonic components. The cutoff frequency and attenuation rate of the filter circuit 5 can be set as appropriate so that harmonic components can be efficiently removed. The cut-off frequency is usually set to about 80 to 100 Hz, although it depends on the waveform attenuation (sag) condition.

  As a filter to be used, any known passive filter or active filter can be used. Examples of the passive filter include an RC filter and an LC filter composed of passive elements such as resistors, inductors and capacitors. The active filter is composed of an active element and a passive element, and examples include a filter using a differential circuit or an integration circuit using an operational amplifier.

  Further, filters having frequency characteristics such as Butterworth (maximum amplitude flat type) characteristic, Bessel (maximum delay flat type) characteristic, Chebyshev (amplitude wave) characteristic, simultaneous Chebyshev (elliptic) characteristic, etc. are known. However, any frequency characteristic filter can be used. For example, a filter having simultaneous Chebyshev characteristics is adjusted so as to have a notch in the attenuation region, and a large attenuation gradient can be obtained. Therefore, the filter can be preferably used when it is desired to attenuate the signal sharply in a narrow frequency region. Preferably, the exemplary filter may be configured to obtain an optimum characteristic among the frequency characteristics by combining optimum passive elements or combining optimum passive elements and active elements.

  Further, the filter circuit 5 can be configured in multiple stages by combining a plurality of filters to increase the attenuation rate of harmonic components other than the fundamental component. Examples of such a configuration include at least one low-pass filter (LPF), or a combination thereof with at least one band-pass filter (BPF) or at least one band-eliminate filter (BEF). it can.

  The AD converter circuit 7 is provided to convert the analog voltage signal that has passed through the filter circuit 5 into a digital signal. The converter circuit 7 must be provided upstream of the arithmetic circuit 6 when the arithmetic circuit 6 described later performs digital arithmetic processing. However, when the arithmetic circuit 6 performs analog arithmetic processing, It is not necessary to provide upstream of the arithmetic circuit 6. The output signal of the filter circuit 5 becomes a digital signal or an analog signal depending on whether or not the converter circuit 7 is interposed between the circuit 5 and the arithmetic circuit 6 described later. In order to avoid the complexity described separately, the “output (signal) of the filter circuit 5” is hereinafter referred to as “input signal to the arithmetic circuit 6”.

Arithmetic circuit 6, as described above, the waveform of the input signal input thereto, a phase angle with respect to the waveform of the input signal 90 ° × (2m-1) (m is an integer of 1 or more) was shifted by (the N 1 or more integer) N cycles of each fundamental component two waveforms of a waveform waveform or period is shifted by [pi / 2 [omega extracted only, for each waveform, a half period of the fundamental wave component as well as the integration as the integration interval, in terms of the half cycle wherein a is sign inverted subsequent to the half cycle of the next instantaneous value of each waveform was performed sequentially integrating integrating operation at least once each as an integration section, these The integration result is added for each of the two waveforms, and the square root of the sum of squares of the two addition results is calculated to obtain the effective value of the leakage current.

First, with reference to FIG. 2 and the following equations (Equation 1 to Equation 5), the arithmetic processing for obtaining harmonic current component removal and the fundamental current component effective value in the arithmetic circuit 6 will be described. In FIG. 2, the vertical axis represents the amplitude of the waveform, and the horizontal axis represents time (the rotation angle corresponding to each time is in parentheses). In order to simplify the explanation, the input signal to the arithmetic circuit 6 is composed of a fundamental wave component and a second harmonic component advanced by a phase angle φ (φ is an arbitrary value). assume from the reference time point t _0, which is set appropriately as to extract one cycle of the waveform of the fundamental wave component. In this case, the instantaneous value of the waveform of the input signal can be expressed by the following equation using a Fourier series.

（式中、位相角ψは任意の値を示す。）

(In the formula, the phase angle ψ represents an arbitrary value.)

For one waveform extracted from this input signal, the half-cycle (t ₀ + π / ω) of the fundamental wave component is integrated from the reference time t ₀ as an integration interval, and the value of A is obtained. Result is obtained. A indicates a value obtained by subtracting the area of the lower hatched portion from the area of the upper hatched portion of the horizontal axis (time axis) of the second waveform from the top in FIG.

Next, with respect to the input waveform to the arithmetic circuit, the expression of the instantaneous value is inverted between positive and negative, and the half value (t0 + π / ω to t0 + 2π / ω) continuous to the integration interval is integrated in the same manner as the integration interval to obtain the value of B Is obtained, the result of the following equation (Equation 3) is obtained. B indicates a value obtained by subtracting the area of the hatched portion content of lower from the area of the shaded portion of the upper than the horizontal axis of the third stage of the waveform from the top in FIG. 2.

Furthermore, it performs integration similarly for waveform obtained by shifting by a predetermined phase angle from the instantaneous value of the waveform of the reference time point t _0. Here it will be described one cycle of the waveform to be extracted from the reference time point t ₀ by shifting the phase angle only 90 °. The phase angle can be set to 90 ° × (2m−1) (m is an integer of 1 or more), that is, 90 °, 270 °, 450 °, 630 °, 810 °, etc. For convenience of explanation, the angle is 90 °.

For the other waveforms of one cycle, which is the extraction, the formula of the half period of the fundamental wave component similar to the equation shown in Equation 2 and Equation 3 is integrated as an integral interval, also the instantaneous value of the other waveform When the values of C and D are obtained by reversing the positive and negative values and integrating the next half cycle following the half cycle as an integration interval , the following formulas (Equations 4 and 5) are obtained. C and D respectively correspond to the value obtained by subtracting the area of the hatched portion content of lower from the area of the shaded portion of the upper than the horizontal axis of the fourth stage and fifth stage of the waveform from the top in FIG. 2.

The C and D can be obtained by the same integration by extracting a waveform that is shifted by a period π / 2ω from the reference time t ₀ by one cycle of the fundamental wave component. Actually, as mentioned above, it is difficult to design a circuit that extracts two waveforms by shifting them precisely by a predetermined phase angle. On the other hand, a timer is mounted on the circuit to extract two waveforms according to their period. when considering the ability to easily realized by, in some cases the person who performs a predetermined period shifted waveform by extracting only one cycle of the integration is preferred.

As apparent from the equations shown in Equations 2 to 5, the integration results for the second-order harmonic components in the second term on the right side of the equations A to D are all 0, resulting in the second-order harmonic components being The integrated value of the current waveform of only the fundamental wave component can be obtained. As is clear from these equations, the reference time t ₀ is not necessary to set such a time when the instantaneous value of the fundamental wave component becomes 0, it can be arbitrarily set.

  The case where it is assumed that the input signal to the arithmetic circuit further includes a fourth-order harmonic component advanced by a phase angle ξ (ξ is an arbitrary value) will be described. In this case, the instantaneous value of the waveform of the input signal can be expressed by the following equation (Equation 6) as described above.

（式中、位相角ψ、ξは任意の値を示す。）

(In the formula, phase angles ψ and ξ are arbitrary values.)

  For the instantaneous value of this waveform, when the integration results of A to D are obtained in the same manner as described above, the integration result of the third term on the right side is 0 as shown in the following equation (Equation 7). Similar to the calculation results shown in the equations (2) to (5), the second and fourth harmonic components can be completely removed, and the integrated value of the current waveform of only the fundamental component can be obtained.

  Also, assuming that an odd harmonic component is included in the input signal to the arithmetic circuit 6, by integrating in the same manner as described above, the pair of positive and negative waveforms in the integration interval of the odd harmonic component is canceled. As a result, the integration value for the remaining positive or negative waveform is obtained, and as a result, the integration result can be reduced and the odd harmonic components can be reduced.

  Next, by using the integration results of A to D described above and substituting them into the following equation (Equation 8) to obtain the square root of the sum of squares of the integration results for each waveform, The effective value of the current of the fundamental wave component in the input signal is obtained.

In this way, by performing the above-described arithmetic processing using the integration results from A to D, these waveform functions can be obtained from the equation according to the relationship between the sine wave function and the cosine wave function (sin ² θ + cos ² θ = 1). Since it can be erased, the current effective value of the fundamental wave component in the leakage current can be obtained easily and accurately.

  The arithmetic processing in the case where the waveform corresponding to one cycle of the fundamental wave component included therein is extracted from the input signal to the arithmetic circuit 6 has been described. However, the N cycles of the fundamental wave component are arbitrarily selected from the input signal. It goes without saying that the same arithmetic processing can be performed when waveforms corresponding to (N is an integer of 1 or more) are extracted. In this case, assuming that the waveform signal having the instantaneous value shown in Equation 9 is input to the arithmetic circuit 6 as in the equation shown in Equation 1, the arithmetic processing in the circuit is sequentially performed for each equation shown in Equation 10.

  In actual arithmetic circuit design, it may be set to extract a waveform of 0.1 second (100 milliseconds) corresponding to 10 Hz which is the greatest common divisor of commercial power frequencies 50 Hz and 60 Hz, or an integer multiple thereof. . In this case, the value of N can be set to the number of cycles obtained by dividing 100 milliseconds by the period of the fundamental wave component, or an integer multiple thereof. That is, the number of cycles is N = 5 when the commercial frequency is 50 Hz, and N = 6 when the commercial frequency is 60 Hz. By setting the value of N in this way, the integration calculation can be performed regardless of the commercial frequency.

  An arithmetic circuit for performing such arithmetic processing may be constructed on a substrate by combining various elements, or may be separately constructed on software using a programmable controller or the like.

  The display / output circuit 8 can be used without particular limitation as long as it is configured to display the calculation result in the calculation circuit 6 in a digital or analog manner, or to output to the outside, or to perform both of them.

  The leakage current measuring apparatus 1 of the present invention may be constructed for portable use such as a clamp meter, for example, or may be constructed as another form. Further, by modifying a normally used clamp meter or the like, the leakage current measuring device of the present invention can be provided, or it can be incorporated in a housing of another measuring instrument. Further, the leakage current measuring device 1 of the present invention separates the clamp type current transformer 2 from this, configures the current transformer and the measuring device main body separately, and connects the two with a predetermined signal line. You may do it. In this case, the measuring apparatus main body and the signal line can be connected by a connector.

  Next, the leakage current measuring method of the present invention will be described. In order to measure the leakage current using the leakage current measuring apparatus 1 of the present invention, the clamp type current transformer (leakage current detecting means) 2 is attached to the electric circuit in the same manner as the normal leakage current measurement. After the leakage current signal detected via the current transformer 2 is converted into a voltage signal, the voltage signal is amplified to a signal level that can be calculated, and higher-order harmonic components in the amplified signal are filtered. Remove by circuit. The amplified output signal can be converted to a digital signal as needed.

In the arithmetic circuit includes a waveform of the output signal of the filter circuit, the phase angle 90 ° × the waveform of the output signal (2m-1) (m is an integer of 1 or more) only displaced waveform or the output signal (the N 1 or more integer) N cycles of the fundamental wave component of the two waveforms of a waveform cycle is shifted by [pi / 2 [omega from waveform min extracted corresponds to, for each waveform, a half of the fundamental wave component with integrating the period as an integration section, the integration operation for integrating the next half cycle of the expression of the instantaneous value by sign inversion following the half cycle of the respective waveforms as integration interval after performing at least once each of these integration results are added for each of the two waveforms, and calculates the square root of the sum of squares of the respective addition results performs arithmetic processing for obtaining the effective value of the leakage current, displays the calculated result on a display and output circuits And / Or output. In addition, when the signal after this arithmetic processing is an analog signal, it can AD-convert into a digital signal.

  Hereinafter, measurement examples using the leakage current measuring apparatus of the present invention will be described. In the measurement, a passive element optimal for the filter circuit (LPF) of the leakage current measuring device of the present invention was selected and used so that the third and higher harmonic components in the leakage current could be removed.

[Measurement Example 1]
Use a measuring instrument with harmonic analysis function to detect the leakage current of electrical equipment that contains a lot of secondary harmonic components (single-phase circuits for general fluorescent lamps in stores, etc.), and its waveform and harmonic content The results of measuring are shown in Table 1 and FIG. As shown in FIGS. 3A and 3B, the leakage current contains a large amount of particularly low-order even harmonics, and the waveform thereof has a saw-tooth shape.

  As a result of obtaining the leakage current value of the same electrical equipment using a commonly used clamp meter, it is 50.99 mA when the filter function is not used (see Table 1), and 35.44 mA when the filter function is used. The current value of the fundamental wave component of 1 was larger than 2.16 mA. The commercial frequency is 60 Hz.

  As a result of detecting the leakage current flowing out from the facility using the leakage current measuring apparatus of the present invention for the same electrical equipment, the displayed value is consistent with the value of the fundamental wave of the harmonic content in Table 1, and is 2.16 mA. showed that. This is because the third and higher harmonic components are removed by the filter circuit of the leakage current measuring apparatus of the present invention, and the second harmonic component is also removed by the arithmetic circuit.

[Measurement Example 2]
Table 3 and FIG. 4 show the results of detecting the leakage current of the inverter type fluorescent lamp using a measuring instrument having a harmonic analysis function and measuring the waveform and the harmonic content. As shown in FIGS. 4A and 4B, the leakage current contains a large amount of low-order, especially second-order and fourth-order even harmonics, and the waveform thereof has a saw-tooth shape.

  As a result of obtaining the leakage current value of the same inverter type fluorescent lamp using a normally used clamp meter, it is 0.038 mA when the filter function is not used, and 0.029 mA when the filter function is used. The current value was larger than 0.009 mA. The commercial frequency is 60 Hz as in the case of Test Example 1.

  As a result of detecting the leakage current flowing out from the equipment using the leakage current measuring device of the present invention for the same inverter type fluorescent lamp, the displayed value is consistent with the value of the fundamental wave of the harmonic content rate in Table 2, 0.009 mA. This is because the third and higher harmonic components are removed by the filter circuit of the leakage current measuring apparatus of the present invention, and the second harmonic component is also removed by the arithmetic circuit.

  As described above, by using the leakage current measuring apparatus and measurement method of the present invention, it is possible to remove higher-order harmonic components and lower-order harmonic components, and to measure leakage current more accurately and quickly. In addition, it is possible to obtain an effective effective value of leakage current by adjusting each filter so that the third and higher harmonic components can be cut by combining a plurality of predetermined filters in the filter circuit. Can do.

  The leakage current measuring apparatus and measuring method according to the present invention are particularly applied to electrical equipment having a high-frequency output type inverter circuit that outputs a high-frequency signal to an input signal.

It is a figure which shows an example of embodiment of the leakage current measuring apparatus of this invention. It is a figure explaining the outline | summary of the arithmetic processing in an arithmetic circuit. It is a figure which shows an example of the measurement result of the leakage current from an electrical installation. It is a figure which shows an example of the measurement result of the leakage current from an inverter type fluorescent lamp. It is a figure which shows an example of the measurement result of the leakage current from a normal electrical installation. It is a figure which shows an example of the measurement result of the leakage current from the fluorescent lamp provided with the copper-iron type ballast.

Explanation of symbols

1 Leakage current measuring device 2 Clamp-type current transformer 3 Shunt resistance (conversion circuit)
4 Amplifying circuit 5 Filter circuit 6 Arithmetic circuit 7 AD converter circuit 8 Display / output circuit

Claims (6)

A leakage current detecting means for detecting a leakage current signal including a fundamental wave component and a harmonic component of an electric circuit; a conversion circuit for converting the leakage current signal into a voltage signal; and an amplification circuit for amplifying the voltage signal; Leakage current comprising at least a filter circuit that removes higher-order harmonic components in the output signal from the amplifier circuit, an arithmetic circuit, and a display / output circuit that displays and / or outputs the arithmetic result of the arithmetic circuit A measuring device,
The arithmetic circuit is:
The output waveform of the filter circuit that is input to this, and a waveform in which the phase angle is shifted by 90 ° × (2m−1) (m is an integer of 1 or more) relative to the output waveform , or the period is π from the output waveform Two waveforms with a waveform shifted by / 2ω are extracted corresponding to N cycles (N is an integer of 1 or more) of the fundamental component,
For each waveform, the half cycle of the fundamental wave component is integrated as an integration interval, and the instantaneous value expression of each waveform is inverted, and the next half cycle following the half cycle is integrated as an integration interval. The integration results are added to each of the two waveforms, and the square root of the sum of squares of the two addition results is calculated to obtain the effective value of the leakage current. Leakage current measuring device characterized by that.   The filter circuit is composed of at least one low-pass filter (LPF) or a combination thereof with at least one band-pass filter (BPF) or at least one band-eliminate filter (BEF). The leakage current measuring apparatus according to claim 1, wherein the component can be removed or reduced.   The leakage current measuring device according to claim 1 or 2, wherein the value of N is set to the number of cycles obtained by dividing 100 milliseconds by the period of the fundamental wave component, or an integer multiple thereof.   The leakage current measuring device according to claim 1, which is used for measuring a leakage current of a high-frequency output type inverter circuit. A leakage current detection means is mounted on the electric circuit, thereby detecting a leakage current signal composed of a fundamental wave component and a harmonic component, a conversion step of converting the leakage current signal into a voltage signal and outputting the voltage signal, and the voltage An amplification step for amplifying a signal, a filter step for removing higher-order harmonic components in the output signal from the amplification circuit, an arithmetic processing step, and a display for displaying and / or outputting an arithmetic result in the arithmetic processing step A leakage current measuring method including at least an output process,
The arithmetic processing step includes
An output waveform of the filter process is input thereto, the phase angle 90 ° × respect to the output waveform (2m-1) (m is an integer of 1 or more) the period from shifted by waveform or the output waveform π Two waveforms with a waveform shifted by / 2ω are extracted corresponding to N cycles (N is an integer of 1 or more) of the fundamental component,
For each waveform, the half cycle of the fundamental wave component is integrated as an integration interval, and the instantaneous value expression of each waveform is inverted, and the next half cycle following the half cycle is integrated as an integration interval. The integration results are added to each of the two waveforms, and the square root of the sum of squares of the two addition results is calculated to obtain the effective value of the leakage current. Leakage current measuring method characterized by the above.   6. The leakage current measuring method according to claim 5, wherein the value of N is set to the number of cycles obtained by dividing 100 milliseconds by one period of the fundamental wave component or an integer multiple thereof.

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