JP6106992B2 - Insulation resistance measuring device - Google Patents

Description

  The present invention relates to an insulation resistance measuring method and apparatus capable of measuring the insulation resistance of an AC circuit in a live line (energized) state.

  Insulation resistance measurement of AC circuits and various devices is carried out exclusively in an unenergized state using an insulation resistance meter called a megger. Or, for a general three-phase AC circuit, ground the Y-connected neutral point and measure the current flowing through this neutral point to detect the ground fault (decrease in insulation resistance) of each phase. ing. Moreover, the insulation resistance of each phase is also measured by detecting the imbalance of the current between each phase in a single-phase or three-phase AC circuit.

  On the other hand, the present applicant previously proposed a method of measuring the insulation resistance between DC electric circuits in a live line (energized) state (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 4525630 JP 2009-31187 A

  However, the techniques introduced in Patent Documents 1 and 2 are effective in measuring the insulation resistance between DC electric circuits, but cannot measure the insulation resistance between AC electric circuits in a live line (energized) state. Specifically, when the AC circuit is ungrounded, such as power supply equipment for ships, for example, each phase of the three-phase AC circuit can be Y-connected while the live (energized) state is maintained, and the neutral point can be grounded. Since this is not possible, it is very difficult to measure the insulation resistance of each phase.

  The present invention has been made in view of such circumstances, and its purpose is to easily and continuously measure the insulation resistance between AC circuits in a live line (energized) state. It is to provide a measuring method and apparatus.

In order to achieve the above-mentioned object, the insulation resistance measuring method according to the present invention is:
For example, the positive reference voltage for the neutral point between the AC circuits is obtained between the positive and negative electrodes of the DC voltage obtained by full-wave rectification of the voltage between the ungrounded single-phase or three-phase AC circuits. And a first voltage dividing resistor circuit and a second voltage dividing resistor circuit for obtaining a negative reference voltage with respect to the neutral point are connected in series, and the first and second voltage dividing resistor circuits are connected in series. A detection resistor for detecting a voltage generated at the neutral point between the point and the ground point,
A DC reference voltage obtained by adding the positive side reference voltage and the negative side reference voltage obtained by the first and second voltage dividing resistor circuits, respectively, is used as the detection voltage at the neutral point obtained by the detection resistor. And dividing the divided value by a predetermined constant to obtain the insulation resistance of the AC circuit.

The insulation resistance measuring apparatus according to the present invention is
For example, a full-wave rectifier circuit that rectifies the voltage between ungrounded single-phase or three-phase AC circuits to obtain a DC voltage,
A positive-side reference voltage with respect to the neutral point of the AC circuit by dividing the DC voltage output from the full-wave rectifier circuit connected in series and interposed between output terminals consisting of the positive and negative electrodes of the full-wave rectifier circuit And first and second voltage-dividing resistor circuits for obtaining the negative-side reference voltage and
A detection resistor for detecting a voltage generated at the neutral point by interposing the first and second voltage dividing resistor circuits between a series connection point and a ground point;
A first insulation converter for extracting the positive side reference voltage from the alternating current circuit side in an isolated manner;
A second insulation converter for extracting the negative reference voltage from the alternating current circuit side separately from each other;
The positive reference voltage and the negative reference voltage obtained via the first insulation converter and the second insulation converter are rectified with the same polarity, and the signals obtained by rectification are matched. A reference voltage signal generation circuit that obtains one reference voltage signal later through a low-pass filter;
A third insulation converter for extracting the neutral point voltage determined by the detection resistor from the alternating current circuit side in an isolated manner;
A detection voltage generation circuit that obtains a detection voltage signal through a low-pass filter after rectifying the detection voltage obtained via the third isolation converter;
And an arithmetic circuit for dividing the reference voltage signal by the detection voltage signal and multiplying the divided value by a predetermined coefficient to obtain an insulation resistance between the AC electric circuits.

  Preferably, the insulation resistance measuring device further displays a display device that displays the insulation resistance of the AC circuit obtained by the arithmetic circuit, and issues an alarm when the insulation resistance of the AC circuit is below a set value. It is desirable to provide an alarm.

  Incidentally, the first and second voltage dividing resistor circuits are resistor circuits of the same specification in which a first resistor having a high resistance value and a second resistor having a low resistance value are directly connected to each other. The series connection of the second voltage dividing resistor circuit is formed by connecting the second resistors in each voltage dividing resistor circuit to each other and setting the connection point as a neutral point with respect to the AC circuit.

  For the reference voltage signal generation circuit and the detection voltage generation circuit, after rectifying the reference voltage signal and the detection voltage signal extracted through the first to third isolation converters, It is preferable that the output is made through a low-pass filter.

  According to the insulation resistance measuring method and apparatus having the above configuration, even when the single-phase or three-phase AC circuit is in a live line (energized) state, the insulation resistance between the phases of the AC circuit can be continuously measured. Therefore, it is not necessary to stop the operation of various devices connected to the AC circuit each time when measuring the insulation resistance. Especially for non-grounded AC circuits, the insulation resistance between each phase in the live line state can be measured continuously. For example, in order to ensure safe navigation by monitoring ship power supply equipment, Effects such as extremely high usefulness are exhibited.

The figure which shows the whole schematic structure of the insulation resistance measuring apparatus which concerns on one Embodiment of this invention. The signal waveform diagram for demonstrating the insulation resistance measurement between three-phase alternating current electric circuits. The measurement principle figure for demonstrating the insulation resistance measuring method which concerns on one Embodiment of this invention.

  Hereinafter, an insulation resistance measuring method and an insulation resistance measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  1 is a diagram showing a schematic overall configuration of an insulation resistance measuring apparatus according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation, and FIG. 3 is a measurement principle of an insulation resistance measuring method. It is a figure for demonstrating. This insulation resistance measuring method and insulation resistance measuring apparatus measure the insulation resistance of a three-phase AC circuit (U-phase, V-phase, W-phase) of an AC power supply AC. Based on the voltage generated at the neutral point (U phase, V phase, W phase), the current flowing between the three phase AC circuits is detected, and the three phase AC circuit (U phase, V phase, W phase) is detected from this current. ) Is configured to obtain an insulation resistance between the two.

  As shown in FIG. 1, this insulation resistance measuring device is composed of six diodes D1 to D6 each connected between the U-phase, V-phase, and W-phase electric circuits of the three-phase AC circuit to be measured. DC voltage VP obtained by the positive half cycle of each phase and DC voltage obtained by the negative half cycle, connected between the wave rectifier circuit 10 and the output terminal comprising the positive electrode and the negative electrode of the full wave rectifier circuit 10 A series resistance circuit 20 for detecting VN is provided.

  The series resistor circuit 20 includes a first voltage dividing resistor circuit 21 in which a first resistor R1a having a high resistance value and a second resistor R1b having a low resistance value are connected in series, and a first resistor R2a having a high resistance value. And a second voltage dividing resistor circuit 22 in which a low resistance second resistor R2b is connected in series. In particular, the two sets of voltage dividing resistor circuits 21 and 22 form a resistor circuit having the same specification, and a connection point between the second resistors R1b and R2b is a neutral point M with respect to the three-phase AC circuit.

  The series resistance circuit 20 divides the DC voltage (VP + VN) obtained between the positive and negative output terminals of the full-wave rectifier circuit 10 according to the resistance value ratio. The series resistor circuit 20 includes a positive reference voltage VR1 in a positive half cycle and a negative electrode in a negative half cycle with reference to the voltage at the neutral point M, which is a connection point of the second resistors R1b and R2b. It plays the role which calculates | requires each side reference voltage VR2.

  Further, a detection resistor R3 for detecting a neutral point voltage VR3 generated at the neutral point M is interposed between the neutral point M and the earth ground (grounding point) E in the series resistance circuit 20. ing. The resistor circuit composed of the resistors R1a, R1b, R2a, R2b and the detection resistor R3 constituting the voltage dividing resistor circuits 21, 22 generates an AC voltage between the U-phase, V-phase, and W-phase forming the three-phase AC circuit. A so-called T-type voltage detection circuit for the DC voltage (PV + PN) obtained by full-wave rectification is configured.

Now, assuming that the resistance values of the resistors R1a, R1b, R2a, R2b, R3 are r1a, r1b, r2a (= r1a), r2b (= r1b), r3, respectively, the current IP flowing through the series resistor circuit 20 is
IP = (VP + VN) ÷ (r1a + r1b + r2a + r2b)
It becomes.

The positive reference voltage VR1 and the negative reference voltage VR2 generated between both ends of the second resistors R1b and R2b are as follows:
VR1 = IP × r1b, VR2 = IP × r2b
It becomes.

  On the other hand, the insulation resistances with respect to the earth ground (grounding point) E of the U phase, V phase, and W phase constituting the three-phase AC circuit are respectively Rux, Rvx, and Rwx. The values of these insulation resistances Rux, Rvx, Rwx are inherently infinite because the three-phase AC circuit is not grounded. Further, the U-phase, V-phase, and W-phase voltages forming the three-phase AC circuit change with their phases shifted by 120 ° as shown in FIGS. The rectified voltage waveform obtained by full-wave rectifying the U-phase, V-phase, and W-phase voltages via the full-wave rectifier circuit 10 is a DC voltage (VP + VN) as shown in FIG. Become.

Assuming that the U-phase insulation resistance Rux is lowered, in the positive half cycle of 0 to 180 ° in the U-phase, the ground current flowing from the U-phase through the insulation resistance Rux as shown in FIG. Iux further flows into the V phase through the detection resistor R3, the resistor R2b, the resistor R2a, and the diode D4 in this order. The ground current Iux at this time is expressed as Vux when the voltage between the U phase and the V phase is Vuv. Iux = Vuv ÷ (Rux + r3 + r2b + r2a)
It becomes.

And VR3 = Iux × r3 at both ends of the detection resistor R3
A voltage VR3 is generated. This voltage VR3 is a voltage (neutral point voltage) of the neutral point M with respect to the earth ground (grounding point) E.

During the positive half cycle, the voltage Vuv between the U phase and the V phase is applied to the positive electrode of the rectifier circuit 10 via the diode D1 of the rectifier circuit 10 as shown in FIG. It is output as VP (= Vuv). Then, as described above, VR1 = IP × r1b is caused in the resistor R1b by the current IP flowing through the series resistor circuit 20 to which the voltage VP is applied.
A positive reference voltage VR1 is generated.

  Here, the value r1a of the first resistor R1a in the first voltage dividing resistor circuit 21 is sufficiently larger (for example, 100 times or more) than the value r1b of the second resistor R1b that generates the positive reference voltage VR1. The value r3 of the detection resistor R3 is sufficiently larger than the value of the insulation resistance Rux (for example, 100 times or more). At the same time, it is assumed that the value r1b of the second resistor R1b is equal to the value r3 of the detection resistor R3 (r1b = r3).

Then, the voltage ratio between the positive reference voltage VR1 and the voltage VR3 in the positive half cycle is
VR1 / VR3 = IP / Iux
≒ (VP ÷ r1b) / (Vuv ÷ Rux)
= Rux / r1b
And is proportional to the reciprocal of the ratio of the resistance values of the second resistor R1b and the insulation resistor Rux. Therefore, if the voltage ratio between the positive reference voltage VR1 and the voltage VR3 is obtained and multiplied by the value r1b of the second resistor R1b, the value of the insulation resistance Rux can be obtained. Become.

Similarly, in the negative half cycle of 180 to 360 degrees in the U phase, as shown in FIG. 3, the ground current Iux through the insulation resistance Rux is changed from the V phase to the diode D3, the resistance R1a, the resistance R1b, and the detection resistance. It flows to the U phase via R3 and the insulation resistance Rux in order. The ground current Iux in this negative half cycle is expressed as Iux = Vvu / (r1a + r1b + r3 + Rux) where Vvu is the voltage between the V phase and the U phase.
VR3 = Iux × r3 at both ends of the detection resistor R3
A voltage VR3 is generated.

In this negative half cycle, the voltage Vvu between the U phase and the V phase is obtained as the voltage VN at the negative electrode via the diode D2 of the rectifier circuit 10. Therefore, the voltage ratio between the negative reference voltage VR2 and the voltage VR3 is VR2 / VR3 = IP / Iux as in the case of the positive half cycle described above.
≒ (VN ÷ r2b) / (Vvu ÷ Rux)
= Rux / r2b
And is proportional to the reciprocal of the ratio of the resistance values of the second resistor R2b and the insulation resistor Rux. Therefore, if the voltage ratio between the negative reference voltage VR2 and the voltage VR3 is obtained and multiplied by the value r2b of the second resistor R2b, the value of the insulation resistance Rux can be obtained. Become.

  That is, in the positive half cycle (0 to 180 °) and the negative half cycle (180 to 360 °) in the U phase, a gap between both ends of the detection resistor R3 is caused by a decrease in the insulation resistance Rux of the U phase. A voltage VR3 alternating between positive and negative is generated. At this time, voltages VP and VN rectified according to the U-phase voltage changes Vuv and Vvu are alternately output to the positive and negative electrodes of the rectifier circuit 10. Therefore, according to the positive half cycle (0 to 180 °) and the negative half cycle (180 to 360 °) in the U phase, the voltage ratio between the positive reference voltage VR1 or the negative reference voltage VR2 and the voltage VR3 is changed. If obtained, the value of the U-phase insulation resistance Rux can be calculated according to this voltage ratio.

  Similarly, when the insulation resistance Rvx of the V phase decreases, both ends of the detection resistor R3 in the positive half cycle (120 to 300 °) and the negative half cycle (300 to 120 °) in the V phase. In the meantime, an alternating voltage VR3 is generated due to a decrease in the V-phase insulation resistance Rvx. Further, when the insulation resistance Rwx of the W phase is lowered, the detection resistor R3 is connected between both ends of the positive half cycle (240 to 60 °) and the negative half cycle (60 to 240 °) of the W phase. An alternating voltage VR3 is generated due to a decrease in the W-phase insulation resistance Rwx.

  Accordingly, the V-phase or W-phase insulation resistances Rvx and Rwx are also generated at both ends of the positive-side reference voltage VR1 or the negative-side reference voltage VR2 and the detection resistor R3, as in the case of the U-phase. If the voltage ratio with VR3 is obtained, the values of the V-phase or W-phase insulation resistances Rvx and Rwx can be calculated according to this voltage ratio. However, in practice, it is unknown whether the voltage VR3 generated at both ends of the detection resistor R3 is caused by the decrease in the insulation resistance Rux, Rvx, Rwx of the U phase, V phase, or W phase described above. It is.

  Therefore, in the present invention, the voltage VR3 described above is generated alternately according to the voltage changes of the U-phase, V-phase and W-phase in the three-phase AC circuit, and the positive-side reference voltage VR1 and the negative-side reference It is noted that the voltage VR2 can also be detected alternately according to its polarity. At the same time, even if the U-phase, V-phase, and W-phase insulation resistances Rux, Rvx, Rwx cannot be measured individually, if the decrease in the overall insulation resistance of each phase can be measured, the operation of the three-phase AC circuit can be performed. We are paying attention to the fact that the purpose can be sufficiently achieved in managing.

  Accordingly, as shown in FIG. 1, the present insulation resistance measuring apparatus converts the positive reference voltage VR1 and the negative reference voltage VR2 generated between both ends of the resistor R1b and the resistor R2b into first and second insulation converters. (IAP, IAN) 31 and 32 are respectively isolated and extracted from the three-phase AC circuit side, and a voltage V3 detected via the detection resistor R3 is extracted as a third insulation converter (IAM). Through 33, the three-phase AC circuit side is isolated and extracted.

  The voltages VR1, VR2, and V3 extracted through the first to third isolation converters (IAP, IAN, and IAM) 31, 32, and 33 are respectively converted into first and second rectifier circuits (a diode). DP, DE) 41 and 42 are respectively rectified, and then these rectified outputs are filtered through first and second filter circuits (LPP and LPM) 43 and 44, respectively. These rectifier circuits (DP, DE) 41, 42 and filter circuits (LPP, LPM) 43, 44 constitute a part of an arithmetic circuit 40 described later.

  The first rectifier circuit (DP) 41 inverts one polarity of the voltages VR1 and VR2 extracted through the first and second isolation converters (IAP and IAN) 31 and 32, respectively. By rectifying, the polarity of the rectified output is aligned. As a result, the positive reference voltage VR1 in the positive half cycle and the negative reference voltage VR2 in the negative half cycle are obtained as rectified outputs having the same polarity. The rectifier circuit (DP) 41 matches the rectified outputs of the voltages VR1 and VR2 with each other, thereby obtaining the absolute value of the positive reference voltage VR1 and the absolute value of the negative reference voltage VR2 in one cycle. A signal a indicating the reference voltage VR as shown in FIG.

  The filter circuits 43 and 44 are, for example, low-pass filters having a cutoff frequency of 5 Hz. A signal a indicating the reference voltage VR obtained through the rectifier circuit (DP) 41 is smoothed as a signal b through the filter circuit 43 as shown in FIG. Further, the signal c indicating the voltage VR3 obtained through the rectifier circuit (DE) 42, that is, the ground currents Iux, Ivx, which flow as the U-phase, V-phase and W-phase insulation resistances Rux, Rvx, Rwx decrease. The signal c indicating Iwx is smoothed as a signal d as shown in FIGS. 2 (f) to 2 (h) through the filter circuit 44.

  Incidentally, the rectifier circuit (DP) 41 and the filter circuit 43 generate a reference voltage signal (reference voltage signal) b indicating the reference voltage VR based on the positive reference voltage VR1 and the negative reference voltage VR2. A generation circuit is configured. The rectifier circuit (DE) 42 and the filter circuit 44 constitute a detection voltage generation circuit that generates a signal (detection voltage signal) d indicating the voltage VR3 generated in the detection resistor R3.

  Thus, the arithmetic circuit 40 for obtaining the insulation resistance of the three-phase AC circuit includes a divider (DV) 45 and a multiplier (MP) in addition to the rectifier circuits (DP, DE) 41 and 42 and the filter circuits 43 and 44 described above. 46) and a coefficient setting unit 47. Note that the arithmetic processing function of the arithmetic circuit 40 may be realized, for example, as an arithmetic function of a microprocessor.

  The divider (DV) 45 divides the reference voltage VR [signal b] obtained through the filter circuit 43 by the voltage VR3 [signal d] obtained through the filter circuit 44 to obtain the voltage. The ratio [signal e] is obtained. The multiplier (MP) 46 is a coefficient set in the coefficient setter 47 in advance at the output (voltage ratio [signal e]) of the divider (DV) 45 according to the resistance value r3 of the detection resistor R3. By multiplying by K, the U-phase, V-phase, and W-phase insulation resistances Rux, Rvx, Rwx are collectively obtained.

  The display device (IND) 48 displays the insulation resistance (measured value) of the three-phase AC circuit output from the multiplier (MP) 46. The alarm device (AL) 49 warns that the insulation resistance is lowered when the measured insulation resistance (measured value) of the three-phase AC circuit is less than a predetermined insulation resistance value for preventing electric leakage. And information to that effect is sent to a monitoring center (not shown).

  According to the insulation resistance measuring apparatus configured as described above, the voltage ratio [signal e] is obtained by dividing the reference voltage VR [signal b] by the voltage VR3 [signal d]. By simply multiplying the signal e] by the coefficient K, the insulation resistances Rux, Rvx, Rwx of the three-phase AC circuit can be obtained collectively according to the measurement principle described above. In particular, the insulation resistance Rux, Rvx, Rwx of a three-phase AC circuit in a live state is easily measured by effectively using the voltages applied to the U-phase, V-phase, and W-phase of the three-phase AC circuit. can do.

  In addition, the U-phase, V-phase, and W-phase of the three-phase AC circuit are Y-connected, and the insulation resistance Rux, Rvx, Rwx of the three-phase AC circuit in the live state is steady without being grounded to the earth ground E. Can be measured continuously. Then, while displaying the measured insulation resistance using the display device 48, if the insulation resistance is less than the prescribed insulation resistance value, the alarm 49 can be operated to promptly issue an alarm. Therefore, there is a great practical advantage in monitoring the insulation resistance of an ungrounded AC circuit, such as a ship power supply facility.

  Here, specific embodiments of the above-described insulation resistance measurement method and insulation resistance measurement of a three-phase AC circuit using the insulation resistance measurement device will be described. For example, the resistance values r1b and r2b of the second resistors R1b and R2b in the series resistor circuit 20 are set to 1 MΩ, and the reference voltages VR1 and VR2 obtained via the second resistors R1b and R2b are [5V]. The circuit constants of the series resistance circuit 20 are set so that For example, when the insulation resistance Rux is [1 MΩ], the resistance value r3 of the detection resistor R3 is set in advance so that the voltage VR3 generated in the detection resistor R3 by the ground current Iux is [5V]. To do.

  If such a circuit constant is set, for example, when the voltage VR3 is detected as [5V], the output of the divider (DV) 45 becomes [5V ÷ 5V = 1], and the coefficient K is set to [ 1], an insulation resistance measurement value [1 MΩ] can be obtained as the output of the multiplier (MP) 46. If the insulation resistance is [2 MΩ], the voltage VR3 detected via the detection resistor R3 is [2.5V], so that the output of the divider (DV) 45 is [5V ÷ 2.5V = 2], and an insulation resistance measurement value [2 MΩ] can be obtained as the output of the multiplier (MP) 46.

  If the voltage VR3 detected through the detection resistor R3 is [1V], the output of the divider (DV) 45 is [5V ÷ 1V = 5], and the output of the multiplier (MP) 46 is as follows. An insulation resistance measurement value of [5 MΩ] can be obtained. Conversely, if the voltage VR3 detected through the detection resistor R3 is [10V], the output of the divider (DV) 45 is [5V ÷ 10V = 0.5], and the multiplier (MP) 46 As a result, an insulation resistance measurement value of [0.5 MΩ] can be obtained.

  Here, if the coefficient K set in the coefficient setting unit 47 is set to [2], when the voltage VR3 detected via the detection resistor R3 is [5V], the divider (DV) 45 The output is [5V ÷ 5V = 1], and an insulation resistance measurement value of [1 MΩ × 2 = 2 MΩ] can be obtained as the output of the multiplier (MP) 46. Therefore, by setting the coefficient K to [2], the measurement sensitivity (measurement range) is set high so that the insulation resistance Rux can be measured as [1 MΩ] when the voltage VR3 is [10V]. be able to.

  Conversely, when the coefficient K set in the coefficient setting unit 47 is set to [0.2], when the voltage VR3 detected through the detection resistor R3 is [5V], the divider (DV) The output of 45 is [5V ÷ 5V = 1], and an insulation resistance measurement value of [1 MΩ × 0.2 = 0.2 MΩ] can be obtained as the output of the multiplier (MP) 46. Accordingly, by setting the coefficient K to [0.2], the measurement sensitivity (measurement range) is lowered so that the insulation resistance Rux can be measured as [1 MΩ] when the voltage VR3 is [1V]. Can be set.

  Accordingly, it is possible to easily change the measurement range for the insulation resistance only by variably setting the coefficient K. In addition, even if the voltage of the three-phase AC circuit fluctuates, the DC voltage (VP + VN) output through the rectifier circuit 10 varies with the voltage fluctuation, and the series resistance is changed. The current IP flowing through the circuit 20 also changes. The reference voltages VR1 and VR2 also change according to the current IP.

  On the other hand, the ground currents Iux, Ivx, and Iwx flowing through the insulation resistances Rux, Rvx, and Rwx between the U phase, the V phase, and the W phase also change in accordance with the voltage variation of the three-phase AC circuit. As the ground currents Iux, Ivx, and Iwx change, the voltage VR3 generated in the detection resistor R3 also changes, and the amount of change is proportional to the amount of change in the reference voltages VR1 and VR2. Therefore, the value of the insulation resistance obtained by the above-described calculation is kept constant without being affected by the voltage fluctuation of the three-phase AC circuit. Therefore, it is possible to measure the insulation resistance between the three-phase AC circuits without regard to fluctuations in the power supply voltage.

  The present invention is not limited to the embodiment described above. Here, the insulation resistance measurement between the three-phase AC circuits has been described as an example, but it is needless to say that the measurement can be similarly applied to the measurement of the insulation resistance between the single-phase AC circuits. The resistance values r1a, r1b, r2a, r2b, r3 of the resistors R1a, R1b, R2a, R2b, R3 may be determined according to the power supply voltage specifications of the AC circuit to be measured. Furthermore, in the said embodiment, it demonstrated on the assumption that the said 1st-3rd isolation | separation converter (IAP, IAN, IAM) 31,32,33 performs the voltage signal conversion of [1: 1]. However, these isolation converters (IAP, IAN, IAM) 31, 32, 33 may perform [1: n] voltage signal conversion to increase the measurement sensitivity. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

10 full wave rectifier circuit 20 series resistor circuit 21, 22 voltage dividing resistor circuit R1a, R1b, R2a, R2b resistor R3 detection resistor 31, 32, 33 insulation converter (IAP, IAN, IAM)
40 arithmetic circuit 41, 42 second rectifier circuit (DP, DE)
43,44 Filter circuit (LPP, LPM)
45 Divider (DV)
46 Multiplier (MP)
47 Coefficient setting device 48 Display device (IND)
49 Alarm (AL)

Claims (4)

A full-wave rectifier circuit that obtains a DC voltage by rectifying the voltage between the AC circuits;
A positive-side reference voltage with respect to the neutral point of the AC circuit by dividing the DC voltage output from the full-wave rectifier circuit connected in series and interposed between output terminals consisting of the positive and negative electrodes of the full-wave rectifier And first and second voltage-dividing resistor circuits for obtaining the negative-side reference voltage and
A detection resistor for detecting a voltage generated at the neutral point by interposing the first and second voltage dividing resistor circuits between a series connection point and a ground point;
A first isolation converter for extracting the positive reference voltage from the AC circuit side in an isolated manner;
A second isolation converter that extracts the negative reference voltage from the AC circuit side by isolation, and
The positive reference voltage and the negative reference voltage obtained via the first insulation converter and the second insulation converter are rectified with the same polarity, and the signals obtained by rectification are matched. A reference voltage signal generation circuit for obtaining one reference voltage signal later through a low-pass filter;
A third isolation converter that extracts the neutral point voltage obtained by the detection resistor by isolation from the AC circuit side; and
A detection voltage generation circuit that obtains a detection voltage signal through a low-pass filter after rectifying the detection voltage obtained via the third isolation converter;
An insulation resistance measuring apparatus comprising: an arithmetic circuit for dividing the reference voltage signal by the detection voltage signal and multiplying the divided value by a predetermined coefficient to obtain an insulation resistance of the AC circuit. The insulation resistance measuring apparatus according to claim 1 ,
Insulation resistance further comprising: a display device that displays the insulation resistance of the AC circuit obtained by the arithmetic circuit; and an alarm device that issues an alarm when the insulation resistance of the AC circuit is below a set value. measuring device. It said first and second voltage dividing resistor circuit is a resistor circuit that the second resistor and the directly connected each of the first resistor and the low resistance value of the high resistance value,
In the series connection of the first and second voltage dividing resistor circuits, the second resistors in each voltage dividing resistor circuit are connected to each other, and the connection point is set as a neutral point with respect to the AC circuit. The insulation resistance measuring apparatus according to claim 1 or 2 . The insulation resistance measuring apparatus according to claim 1 or 2 , wherein the AC circuit is a non-grounded single-phase or three-phase AC circuit.

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