JP5218823B2 - Capacitor leakage current measuring method and capacitor leakage current measuring apparatus - Google Patents

Description

  The present invention relates to a capacitor leakage current measuring method and a capacitor leakage current measuring apparatus for measuring a capacitor leakage current.

  The method for measuring the leakage current of a capacitor generally follows the provisions of 4.9 of JIS C 5101-1, which is a Japanese industrial standard. This regulation is “Apply a DC voltage to the capacitor and measure it up to about 5 minutes after reaching that voltage. If the specified leakage current value is reached in a short time, it is not necessary to apply it for 5 minutes.” That's it.

  FIG. 7 is an equivalent circuit diagram of a general capacitor C0 involved in leakage current measurement. As shown in FIG. 7, the capacitor C0 is equivalently configured by connecting a main capacitance C, an insulation resistance R1, and a dielectric absorption factor D in parallel. The dielectric absorption factor D represents a dielectric polarization formed by an electric field generated inside when a voltage is applied to the capacitor C0 by an internal resistance and a capacitance (hereinafter referred to as dielectric polarization capacitance) connected in series. . As described in Non-Patent Document 1, the dielectric polarization stabilizes after a certain time has elapsed since the start of charging of the capacitor C0, but until the stabilization, the dielectric polarization capacitance is charged via an internal resistance. Is done. Hereinafter, the charging to the dielectric polarization capacitance is referred to as charging to the dielectric absorption factor D.

  As shown in FIG. 7, the dielectric absorption factor D is not necessarily represented equivalently by only one set of internal resistance and dielectric polarization capacitance connected in series, but a set of internal resistance and dielectric polarization capacitance connected in series. May be represented by an equivalent circuit in which a plurality of sets are connected in parallel. Even in such a case, since the time change of the current flowing through the capacitor C0 during charging of the capacitor C0 does not depend on the internal configuration of the dielectric absorption factor D, in FIG. The dielectric absorption factor D is equivalently expressed only by the set.

  The current flowing through the capacitor C0 after the dielectric polarization is stabilized is actually a leakage current flowing through the insulation resistance R1. Therefore, in order to accurately measure the leakage current of the capacitor C0, it is necessary to measure the leakage current after the dielectric polarization is stabilized. By measuring this leakage current, the insulation resistance R1 can also be obtained.

  FIG. 8 is a diagram showing a time change of the current flowing through the capacitor C0 when charging is performed by applying a specified voltage to the capacitor C0. The horizontal axis represents time and the vertical axis represents the current flowing through the capacitor C0. A region X in FIG. 8 is a charging current region, and the main capacitor C is mainly charged. The region Y is a dielectric absorption region, and the dielectric absorption factor D is charged. A region Z is a leakage current region after the dielectric absorption factor D is sufficiently charged, and the leakage current is measured in this region.

  Since it takes a certain amount of time to charge the dielectric absorption factor D in the dielectric absorption region Y, the time from application of the specified voltage to the capacitor C0 until reaching the leakage current region Z also becomes long. The above JIS C 5101-1 rule that “a DC voltage is applied to the capacitor and measured approximately 5 minutes after reaching that voltage” is charged with the above dielectric absorption factor D, and the leakage current If the leakage current is not measured after reaching the area, it means that an accurate current value cannot be measured.

  However, since it takes time to charge the individual capacitors C0 in this case, pay attention to the latter half of this rule “if the specified leakage current value is reached in a short time, it is not necessary to apply for 5 minutes”. In order to cope with this, several methods for reaching the leakage current region in a short time have been proposed.

For example, in Patent Document 1, charging is performed in a plurality of times, the charging period per time is shortened, and the charging voltage is controlled for each charging period, and a high voltage is applied to the capacitor within a possible range. Apply to achieve fast charging.
Electrical Engineering Handbook (6th edition), pages 110, 181 JP-A-10-115651

  However, the method of Patent Document 1 has the following problems.

  FIG. 9 is a plan view of a conventional leakage current measuring apparatus. A workpiece composed of the capacitor C0 to be measured is conveyed to the separation supply unit 2 by the linear feeder 1. The separation supply unit 2 stores individual workpieces one by one in a plurality of workpiece storage holes 4 arranged at equal intervals around the circular transfer table 3. The transport table 3 can be intermittently rotated around the central axis 5 in, for example, the direction A shown in the figure, and a plurality of charging stages 6 and measurement stages 7 are spaced apart from each other along the peripheral edge of the transport table 3. They are spaced apart.

  Two probes (not shown in FIG. 9) are provided on the bottom surfaces of the plurality of charging stages 6 so as to be movable up and down with respect to the electrodes provided at both ends of the workpiece. When the workpiece storage hole 4 comes to the position of the charging stage 6 as the transfer table 3 moves, the two probes come into contact with both end electrodes of the workpiece to charge the workpiece initially.

  While the workpiece is moving between the plurality of charging stages 6 or between the charging stage 6 and the measurement stage 7, the probe is not in contact with both end electrodes of the workpiece, and the charge accumulated on the workpiece is naturally discharged. The As can be seen from the equivalent circuit of FIG. 7, during this discharge period, the charge stored in the main capacitor C is used for charging the dielectric absorption factor D and consumed as a current flowing through the insulation resistor R1.

  In the measurement stage 7, a measurement probe is brought into contact with a work terminal, and a leakage current is measured while applying a specified DC voltage. The measurement stage 7 and the charging stage 6 in front of the measurement stage 7 are arranged at a distance from each other, and a part of the charge of the main capacity C of the work is discharged until the work reaches the measurement stage 7. For this reason, it is necessary to measure the leakage current after fully charging the main capacitor C immediately before measuring the leakage current so that the current flowing through the dielectric absorption factor D can be ignored. Therefore, the sum of the true measurement time required to measure the leakage current and the time required to fully charge the main capacity C is an apparent measurement time, and a considerable time is required until the measurement of the leakage current is completed. (Generally more than 1 minute).

  As described above, the conventional leakage current measuring apparatus has a problem that the measurement time becomes long and the processing efficiency of the measurement is not good. In order to improve the processing efficiency, it may be possible to shorten the charging time by increasing the current that flows when the main capacity C is fully charged. There is also a method of applying a voltage exceeding the nominal value of the withstand voltage. A precision ammeter used at the time of current measurement is generally connected in series with a current limiting resistor, and the current flowing through the main capacitor C is limited. As a result, the charging time of the main capacitor C is reduced. It cannot be shortened significantly.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a capacitor C0 leakage current measuring method and measuring apparatus capable of accurately measuring a leakage current in a short measurement time.

According to one aspect of the present invention, in a leakage current measuring method for measuring a leakage current by applying a DC voltage to a capacitor to be measured,
Charging the capacitor, including a dielectric absorption factor inside the capacitor;
Discharging a charge accumulated in the capacitor through an insulation resistance inside the capacitor for a predetermined period until a potential difference between both ends of the capacitor after charging becomes equal to a potential difference between both ends of the capacitor at the time of leakage current measurement;
Measuring a leakage current flowing through the insulation resistance after the predetermined period,
The impedance at the completion of charging of the first current limiting circuit used in the step of charging the capacitor is set to be smaller than the impedance of the second current limiting circuit used when measuring the leakage current of the capacitor. A characteristic capacitor leakage current measurement method is provided.

Moreover, according to one aspect of the present invention, in a leakage current measuring apparatus that measures a leakage current by applying a DC voltage to a capacitor to be measured,
Charging means for charging the capacitor, including a dielectric absorption factor inside the capacitor;
Discharging means for discharging the charge accumulated in the capacitor through an insulation resistance inside the capacitor for a predetermined period until the potential difference between both ends of the capacitor after charging becomes equal to the potential difference between both ends of the capacitor at the time of leakage current measurement; ,
A leakage current measuring means for measuring a leakage current flowing through the insulation resistance after the predetermined period,
The charging means has a first current limiting circuit connected in series to the capacitor,
The measuring means has a second current limiting circuit connected in series to the capacitor,
An impedance at the time of completion of charging of the first current limiting circuit is set smaller than the impedance of the second current limiting circuit, and a capacitor leakage current measuring device is provided.

  According to the present invention, it is possible to accurately measure a leakage current in a short measurement time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present embodiment is characterized by optimizing the discharge period of the capacitor C0 from the full charge of the capacitor C0 to the leakage current measurement and measuring the leakage current accurately in a short time. Hereinafter, the principle of this embodiment will be described before describing this embodiment in detail.

  As shown in FIG. 7, the capacitor C0 has an equivalent dielectric absorption factor D, and the dielectric absorption current for charging the dielectric absorption factor D sufficiently by charging the dielectric absorption factor D becomes approximately zero. The leakage current of the capacitor C0 cannot be measured with high accuracy until after.

  FIG. 1 is a diagram showing the relationship between the charging time of the capacitor C0 and the dielectric absorption current. As shown in FIG. 8, when the capacitor C0 is charged, the charging current region X shifts to the dielectric absorption region Y and finally reaches the leakage current region Z. That is, in the dielectric absorption region Y, the dielectric absorption factor D is charged, and when it approaches the leakage current region Z, almost no current flows through the main capacitance C and the dielectric absorption factor D. In this state, as shown in FIG. 1, the change amount ΔI = I2−I1 of the dielectric absorption current when the time Δt = t2−t1 is changed becomes a slight value. Therefore, when the time Δt is small, the change amount ΔI of the dielectric absorption current can be ignored.

  In this embodiment, as will be described later, the capacitor C0 is initially charged using at least one charging stage 6 before measurement, and the capacitor C0 is charged to such an extent that the change ΔI of the dielectric absorption current can be almost ignored. Thereafter, the charging is interrupted at least once while the capacitor C0 moves between the charging stages 6, and then the capacitor C0 is connected to the charging stage before measurement provided at a position close to the measuring stage 7. Fully charge main capacity C. When the charging at the pre-measurement charging stage is completed (time t1 in FIG. 1), the capacitor C0 is discharged for the discharge period optimized in advance, and then the leakage current is measured at the measurement stage 7. The present embodiment is characterized in that this discharge period is optimized.

  Further, since the optimized discharge period is extremely small, the change amount ΔI of the dielectric absorption current during the discharge period Δt can be ignored as described above.

  In the prior art, the leakage current was measured after passing through the dielectric absorption region Y and reaching the leakage current region Z, whereas in the present embodiment, before reaching the leakage current region Z, It is noted that the leakage current can be accurately measured by optimizing Δt in a region near the leakage current region Z in the dielectric absorption region Y. This is nothing but a reduction in the time until the start of leakage current measurement.

  2A is an equivalent circuit diagram illustrating the charging operation of the pre-measurement charging stage in a state where no dielectric absorption current flows through the dielectric absorption factor D, and FIG. 2B is a capacitor C0 from the pre-measurement charging stage to the measurement stage 7. FIG. 2C shows an equivalent circuit diagram showing the measurement operation at the measurement stage 7, respectively.

  2A to 2C, it is assumed that no dielectric absorption current flows through the dielectric absorption factor D, and the dielectric absorption factor D can be omitted. Therefore, the capacitor C0 is equivalently represented by a main capacitor C and an insulation resistance R1 connected in parallel.

  The equivalent circuit of FIG. 2A includes a main capacitor C and an insulation resistor R1 connected in parallel, and a current limiting circuit (first current limiting circuit) 8 connected in series to the parallel circuit. The current limiting circuit 8 is either constituted by a resistor or realizes a current limiting function equivalent to the resistor using an electronic component, and the impedance of the current limiting circuit 8 is R2. The impedance R2 is a value when a dielectric absorption current does not flow through the dielectric absorption factor D (that is, when the dielectric absorption factor D is sufficiently charged).

  The equivalent circuit of FIG. 2B has a main capacitor C and an insulation resistor R1 connected in parallel, and is disconnected from the power supply voltage E. In this circuit, the discharge current from the main capacitor C flows through the insulation resistance R1.

  The equivalent circuit of FIG. 2C includes a main capacitor C and an insulation resistor R1 connected in parallel, and a current limiting circuit (second current limiting circuit) 9 connected in series to the parallel circuit. The impedance of the current limiting circuit 9 is R3.

  In the pre-measurement charging stage, the impedance R2 of the current limiting circuit 8 is reduced so that the main capacitor C can be charged in a short time. On the other hand, the impedance R3 of the current limiting circuit 9 is an internal resistance of an ammeter (not shown), and has a relatively large value so that the current can be measured with high accuracy. That is, there is a relationship of R2 <R3. On the other hand, the insulation resistance R1 is larger than R3, and usually has a high impedance on the order of megaohms.

  Here, it is assumed that the power supply voltage E in FIGS. 2A and 2C is equal, the potential difference between both ends of the capacitor C0 in the case of FIG. 2A is V2, and both ends of the capacitor C0 in the case of FIG. Assuming that the potential difference is V3, the relationship of R2 <R3 is established, so that V2> V3. This indicates that the potential difference between both ends of the capacitor C0 gradually decreases within the discharge period after the pre-measurement charging is finished, and becomes V3 when measuring the leakage current. In other words, if the discharge period is set so that the potential difference between both ends of the capacitor C0 after the end of the discharge period becomes V3, the charge / discharge current flows through the capacitor C0 when the probe is connected to the capacitor C0 during the leakage current measurement. The leakage current can be measured immediately.

  Thus, when measuring the leakage current, setting the potential difference across the capacitor C0 to V3 in the shortest possible time is an essential requirement for accurately measuring the leakage current in a short time.

  In order to prevent the charge / discharge current from flowing through the capacitor C0 when measuring the leakage current, it is necessary to set the discharge period t with high accuracy. The optimum value of the discharge period t is expressed by t = C (R3−R2), where C is the capacitance of the capacitor C0. The introduction process of this equation will be described later.

  That is, the main capacitor C is charged with a voltage V2 slightly higher than that at the time of measurement before charging, and then measured by applying a voltage V3 that is slightly lower than V2 at the time of measurement. Assuming that the time from the completion of the pre-measurement charge to the start of measurement is t, the pre-measurement charge voltage V2 decreases due to internal discharge during the time t until the start of measurement, and the potential difference across the main capacitor C is measured at the start of measurement. Therefore, only the leakage current flows through the insulation resistance R1 due to the applied voltage V3 at the start of measurement.

  Here, although the amount of change in the current to the dielectric absorption factor D is ignored, t is obtained as an example below, and the feasibility is examined.

For example, if C = 100 μF, R2 = 100Ω, and R3 = 1 kΩ,
t = 100 × 10 ⁻⁶ (1000−100)
= 9 × 10 ^-3
≒ 1/10 [second]
It becomes.

  According to the present embodiment, initial charging is performed by the charging stage 6, the capacitor is charged to a region close to the leakage current region Z in the dielectric absorption region Y in FIG. 7, and in this state, the capacitor is charged by pre-measurement charging. The battery is charged until the potential difference at both ends reaches V2, and then discharged for a very short time of t = 1/10 [seconds] = 1/600 [minutes], that is, Δt in FIG. R3-R2), and ΔI in the dielectric absorption region close to the leakage current region can be regarded as substantially zero. As described above, the current does not flow into both the main capacitance C and the dielectric absorption factor D, and the leakage current can be measured immediately after the discharge period t has elapsed.

  As described above, according to the present embodiment, the time-consuming initial charging is performed by arbitrarily adjusting the number of the charging stages 6 in advance, and from the pre-measurement charging to the measurement that affects the processing speed of the leakage current measurement, before the measurement. After charging at the charging stage, the discharge period t = C (R3−R2) or discharge is performed for a time close to it, and the leakage current can be measured immediately thereafter. Can be greatly shortened. Further, since the leakage current is measured after charging the capacitor C0 and matching the potential difference between both ends of the capacitor C0 with the measurement voltage, the leakage current can be measured with high accuracy.

  Hereinafter, this embodiment will be specifically described. Hereinafter, the measurement target capacitor C0 for measuring the leakage current is referred to as a work.

  FIG. 3 is a plan view of the capacitor C0 leakage current measuring apparatus according to one embodiment of the present invention. The apparatus of FIG. 3 is similar to the conventional apparatus shown in FIG. 9, and includes a linear feeder 1, a separation supply unit 2, a circular transfer table 3 in which a plurality of work storage holes 4 are formed at equal intervals, and a plurality of An (initial) charging stage 6 and a measurement stage 7 are provided. In addition, the apparatus of FIG. 3 includes a pre-measurement charging stage 10 that is disposed in the vicinity of the charging stage 6 as a configuration that is not shown in FIG. 9. This pre-measurement charging stage 10 is provided for the purpose of fully charging the workpiece immediately before measuring the leakage current of the workpiece which is the capacitor C0 to be measured.

  The pre-measurement charging stage 10 is arranged away from the measurement stage 7 by one interval of the workpiece storage hole 4. Therefore, the work that has reached the pre-measurement charging stage 10 is charged in the same stage, and then reaches the measurement stage 7 when the transfer table 3 is rotated by one interval.

  Each of the plurality of charging stages 6, the pre-measurement charging stage 10, and the measuring stage 7 includes two probes that can move up and down from the bottom surface. The two probes are brought into contact with each other to charge the workpiece or measure the leakage current.

  FIG. 4 is an equivalent circuit diagram in the case where the workpiece is charged at each of the plurality of charging stages 6. In FIG. 4, the capacitor C0 to be measured corresponding to the workpiece is represented by a main capacitance C, an insulation resistance R1, and a dielectric absorption factor D connected in parallel. In this parallel circuit, a current limiting circuit 8 and a switch SW1 are connected in series. This switch SW1 equivalently represents the state of whether or not the probe of the charging stage 6 is brought into contact with both end electrodes of the work. When the switch SW1 is brought into contact, the switch SW1 is turned on and the capacitor C0 is charged. Is called. Since the switch SW1 is turned off when the probe is not brought into contact, the charge accumulated in the main capacitor C is discharged through the insulation resistance R1. The electric charge discharged from the main capacitor C is used to charge the dielectric absorption factor D. As described above, while the workpiece is sequentially transferred to the plurality of charging stages 6, charging of the workpiece and interruption of charging are alternately performed, and charging of the dielectric absorption factor D is performed during the interruption of charging.

  FIG. 5 is an equivalent circuit for charging and leakage current measurement at the pre-measurement charging stage 10 and the measurement stage 7. FIG. 5A is an equivalent circuit diagram in the case where the workpiece is charged at the pre-measurement charging stage 10, and FIG. 5B shows the discharging operation while the workpiece is conveyed from the pre-measurement charging stage 10 to the measurement stage 7. FIG. 5C is an equivalent circuit diagram when the leakage current of the workpiece is measured at the measurement stage 7.

  The equivalent circuits of FIGS. 5A to 5C include a current limiting circuit 8 used for charging in the pre-measurement charging stage 10, a current limiting circuit 9 used for leakage current measurement in the measurement stage 7, and a current. And a switch SW2 for switching whether to connect the current limiting circuit 9 to one end of the work. It is assumed that the power supply 12 having the same voltage level is used for the charging at the pre-measurement charging stage 10 and the leakage current measurement at the measurement stage 7.

  The switch SW2 equivalently represents whether or not the probe is brought into contact with both end electrodes of the work conveyed to the pre-measurement charging stage 10 or the measurement stage 7.

  In the case of FIG. 5A, the switch SW2 is switched when the probe comes into contact with both end electrodes of the workpiece, and the current limiting circuit 8 is connected to one end of the workpiece. Thereby, the current from the power source 12 flows through the current limiting circuit 8 to the main capacitor C in the workpiece (arrow in FIG. 5A), and the main capacitor C is charged.

  While the charging operation of the main capacity C is completed and the work is transported from the pre-measurement charge stage 10 to the measurement stage 7, it is a discharge period, and an equivalent circuit as shown in FIG. 5B is obtained. In this case, excess electric charge accumulated in the main capacitance C of the work is discharged through the insulation resistance R1 (arrow in FIG. 5B).

  When the workpiece reaches the measurement stage 7 and the probe is brought into contact with both end electrodes of the workpiece, the equivalent circuit of FIG. 5C is formed, and the current from the power source 12 is supplied to the current limiting circuit 9 and the current. It flows through the total 11 and the insulation resistance R1, and the leak current is measured by the ammeter 11. The current limiting circuit 9 is an internal resistance of the ammeter 11. This internal resistance must be set to a somewhat large impedance (for example, 1 kΩ) for noise countermeasures. For this reason, when the equivalent circuit of FIG. 5A is directly switched to the equivalent circuit of FIG. 5C, the current flowing through the insulation resistor R1 rapidly increases due to excess charge accumulated in the main capacitor C in FIG. As a result, there is a risk that the measurement of leakage current may be hindered. Therefore, in the present embodiment, a discharge period is provided between the pre-measurement charge and the leakage current measurement, and the excessive charge of the main capacitor C is discharged in advance. Although various discharge methods are conceivable, since the accumulated charge in the main capacitor C spontaneously discharges through the insulation resistance while the work is being conveyed, in this embodiment, the excessive charge in the main capacitor C is utilized using this natural discharge. Is discharged.

  FIG. 6 is a timing chart of charging and leakage current measurement in the pre-measurement charging stage 10 and the measurement stage 7. The transfer table 3 rotates intermittently for each interval of the work storage holes 4. When the workpiece reaches the pre-measurement charging stage 10 at time t1, the probe of the same stage rises and comes into contact with both end electrodes of the workpiece (time t2), and the main capacity C of the workpiece is charged (time t2 to t3).

  When the charging of the workpiece is completed, the probe descends and the discharging operation of the main capacity C starts. Thereafter, the workpiece is conveyed (time t4 to t5).

  At time t5, the workpiece reaches the measurement stage 7, the probe of the same stage rises and contacts both end electrodes of the workpiece, and leakage current measurement is performed (time t6 to t7).

  2 (a) to 2 (c) described above are circuits in which the switch SW2, the ammeter 11 and the dielectric absorption factor D are omitted from FIGS. 5 (a) to 5 (c). The switch SW2 and the ammeter 11 are omitted because they do not affect the operation of the circuit. The reason why the dielectric absorption factor D is omitted is that the dielectric absorption factor D is already sufficiently charged at the time of charging at the pre-measurement charging stage 10 and the current flowing through the dielectric absorption factor D can be ignored. .

The following expression (1) is established from the equivalent circuit of FIG.
V2 = E {R1 / (R1 + R2)} (1)

The following equation (2) is established from the equivalent circuit of FIG.
V3 = E {R1 / (R1 + R3)} (2)

In FIG. 2B, when the discharge time is t, the following equation (3) is established.
V = V2e- ^{t / CR1} (3)

If V = V3 holds, the following equation (4) holds.
E {R1 / (R1 + R3)} = E {R1 / (R1 + R2)} e− ^{t / CR1} (4)

From the above equation (4), the discharge time t is expressed by the following equation (5).
t = −CR1 · ln {(R1 + R2) / (R1 + R3)}
= CR1 · ln {(R1 + R3) / (R1 + R2)}
= CR1 {ln (R1 + R3) -ln (R1 + R2)}
= C {R1 · ln (R1 + R3) −R1 · ln (R1 + R2)}
= C {R1 · lnR1 (1 + R3 / R1) −R1 · lnR1 (1 + R2 / R1)}
= C [R1 {lnR1 + ln (1 + R3 / R1)}
−R1 {lnR1 + ln (1 + R2 / R1)}] (5)

Here, it is known that the following expression (6) holds.

In (6), if X << 1, since a negligible ^{X 2} and subsequent sections (7) holds.
ln (1 + X) ≈X (7)

In the equation (5), the insulation resistance R1 of the capacitor C0 is much larger than the impedances R2 and R3 of the current limiting circuits 8 and 8, and R3 / R1 << 1 and R2 / R1 << 1. , (7) can be used to approximate equation (5), and the following equation (8) is obtained.
t≈C [R1 {lnR1 + R3 / R1} -R1 {lnR1 + R2 / R1}]
= C {R1 · lnR1 + R3-R1 · lnR1-R2}
= C (R3-R2) (8)

  The discharge period t obtained by the equation (8) is an optimum value of the discharge time, and does not necessarily have to be set to the same value as this t. The discharge period between the pre-measurement charging stage 10 and the measurement stage 7 is set so as to be as close as possible to the discharge period t in the equation (8). Actually, the discharge period t can be expressed by equation (8) by adjusting the timing at which the probe is brought into contact with both end electrodes of the workpiece in the pre-measurement charging stage 10 and the measurement stage 7, or by controlling the rotation speed of the transfer stage. Control that approaches is possible. More specifically, the control of the discharge period t can be realized by simple software control.

  Conventionally, the leakage current is measured accurately only after waiting for 2 to 5 times the time constant CR3 between the capacitance C and R3 of the capacitor C0 before the leakage current is measured after the capacitor C0 is charged. However, in this embodiment, it is only necessary to wait for a time shorter than CR3 from the equation (8), and the measurement of the leakage current can be started in a considerably shorter time than in the past.

  As described above, in the present embodiment, first, the workpiece is sequentially conveyed to the plurality of charging stages 6 to sufficiently charge the dielectric absorption factor D in the workpiece. Thereafter, the work is transported to the pre-measurement charging stage 10 adjacent to the measurement stage 7, and the main capacity C in the work is fully charged. Thereafter, while the work is transported to the measurement stage 7, the charge excessively charged in the main capacitor C is discharged through the insulation resistance R1. Thereafter, when the workpiece reaches the measurement stage 7, the leakage current is measured. By optimizing the discharge period between the pre-measurement charging stage 10 and the measurement stage 7, it is possible to shorten the time from the start of charging the workpiece to the measurement of the leakage current, thereby improving the efficiency of the leakage current measurement. . Further, since the leakage current is measured in a state where the dielectric absorption current stops flowing in the workpiece, the measurement accuracy of the leakage current is improved.

  In the above-described embodiment, the example in which the pre-measurement charging stage 10 is provided in proximity to the measurement stage 7 separately from the plurality of charging stages 6 has been described, but instead of providing the pre-measurement charging stage 10 separately, a plurality of charging stages 10 are provided. One of the charging stages 6 may be arranged close to the measurement table. In this case, the contact timing of the probe, the rotation speed of the transfer table 3 and the like so that the discharge period between the charging stage 6 disposed close to the measurement table and the measurement table becomes the time indicated by the above-described equation (8). You can adjust.

  In the embodiment described above, an example in which a plurality of charging stages 6 are installed has been described. However, even when there is only one charging stage 6, the dielectric absorption factor D is sufficiently charged at the time of charging at the pre-measurement charging stage 10. If so, only one charging stage 6 is required.

  In the above-described embodiment, the example in which the main surface of the transfer table 3 is installed in the horizontal direction has been described. However, the present invention is also applied to the case where the main surface of the transfer table 3 is installed in the vertical direction or in the oblique direction. Is possible.

  In the above-described embodiment, an example in which a total of two electrodes are provided at both ends of the workpiece has been described. However, the present invention can also be applied to a workpiece having three or more electrodes. In this case, a probe corresponding to the number of electrodes may be installed on each stage.

  Furthermore, in the above-described embodiment, the example in which the probe is moved in the vertical direction from the bottom surface of each stage has been described. However, the installation location and the movement direction of the probe can be arbitrarily set, for example, the probe is moved from above and below. The probe may be brought into contact with the workpiece, or the probe may be brought into contact with the workpiece by moving horizontally or obliquely from the outer side of the transfer table 3.

  In the above-described embodiment, an example in which the probe is moved up and down at each charging stage to switch whether to contact the workpiece has been described. However, since it takes time to move the probe up and down, When the capacity is small, since the discharge period is short, the discharge period elapses until the probe comes into contact with the workpiece, and the optimum discharge period may not be set. Therefore, for example, in the measurement stage 7 without providing the pre-measurement stage 10, the position of the probe is fixed, and an energizing device including a high-speed switch (for example, FET) is installed between the probe and the work, and this switch May be switched on / off to switch between conduction / interruption of the probe and the workpiece. By adjusting the timing for turning on / off the switch, the discharge period t can be optimized. Such an energizing device may be provided in the initial charging stage 6.

  Moreover, although embodiment mentioned above demonstrated the example which conveys a workpiece | work using the conveyance table 3, you may convey a workpiece | work using an endless belt.

The figure which shows the relationship between the charge time of the capacitor | condenser C0, and a dielectric absorption current. (A) is an equivalent circuit diagram showing the charging operation of the pre-measurement charging stage in a state where the dielectric absorption current does not flow through the dielectric absorption factor D, and (b) is the capacitor C0 conveyed from the pre-measurement charging stage to the measurement stage 7. FIG. 7 is an equivalent circuit diagram showing a measurement operation in the measurement stage 7; The top view of the capacitor | condenser C0 leakage current measuring apparatus which concerns on one Embodiment of this invention. The equivalent circuit diagram in the case of charging a workpiece at each of a plurality of charging stages 6. (A) is an equivalent circuit diagram in the case where the workpiece is charged in the pre-measurement charging stage 10; (b) is an equivalent circuit diagram showing a discharging operation while the workpiece is conveyed from the pre-measurement charging stage 10 to the measurement stage 7; (C) is an equivalent circuit diagram when measuring the leakage current of the workpiece at the measurement stage 7. FIG. 6 is a timing chart of charging and leakage current measurement at the pre-measurement charging stage 10 and the measurement stage 7; The equivalent circuit diagram of the general capacitor | condenser C0 in connection with a leakage current measurement. The figure which shows the time change of the electric current which flows into the capacitor | condenser C0 at the time of charging by applying a specified voltage to the capacitor | condenser C0. The top view of the conventional leakage current measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Linear feeder 2 Separation supply part 3 Conveyance table 4 Work accommodation hole 5 Center axis 6 Charging stage 7 Measurement stage 8, 9 Current limiting circuit 10 Pre-measurement charging stage 11 Ammeter

Claims (14)

In a leakage current measurement method for measuring a leakage current by applying a DC voltage to a capacitor to be measured,
Charging the capacitor, including a dielectric absorption factor inside the capacitor;
Discharging a charge accumulated in the capacitor through an insulation resistance inside the capacitor for a predetermined period until a potential difference between both ends of the capacitor after charging becomes equal to a potential difference between both ends of the capacitor at the time of leakage current measurement;
Measuring a leakage current flowing through the insulation resistance after the predetermined period,
The impedance at the completion of charging of the first current limiting circuit used in the step of charging the capacitor is set smaller than the impedance of the second current limiting circuit used when measuring the leakage current of the capacitor ,
The capacitor leakage current measuring method , wherein the potential difference between both ends of the capacitor at the time of measuring the leakage current is a voltage at which a charging current does not flow through the capacitor when a leakage current measuring probe is connected to the capacitor.   The predetermined period is optimized based on the capacitance of the capacitor, the impedance when the charging of the first current limiting circuit is completed, and the impedance of the second current limiting circuit when measuring the leakage current. The capacitor leakage current measuring method according to claim 1, wherein the capacitor leakage current is measured.   Assuming that the predetermined period is t, the main capacitance of the capacitor is C, the impedance at the completion of charging of the first current limiting circuit is R2, and the impedance of the second current limiting circuit is R3, t = C (R3− 3. The capacitor leakage current measuring method according to claim 2, wherein the predetermined period is optimized so that R2) holds.   The step of charging the capacitor includes the step of alternately charging the capacitor and interrupting charging at least once until no dielectric absorption current flows through the dielectric absorption factor of the capacitor. 4. The capacitor leakage current measuring method according to any one of 1 to 3. 5. The capacitor leakage current measuring method according to claim 4, wherein the step of charging the capacitor further includes a step of charging a main capacity of the capacitor immediately before discharging the capacitor for the predetermined period . Along the transport path of the transport means for transporting the capacitor, at least one initial charging stage, a pre-measurement charging stage, and a measurement stage are sequentially arranged at intervals,
The step of alternately charging the capacitor and interrupting charging at least once is performed using the initial charging stage,
The step of charging the main capacitance of the capacitor immediately before discharging the capacitor for the predetermined period is performed using the pre-measurement charging stage,
The step of measuring the leakage current flowing through the insulation resistance is performed using the measurement stage,
6. The capacitor leakage current measuring method according to claim 5, wherein a discharging period between the pre-measurement charging stage and the measuring stage is set to the predetermined period. Along the transport path of the transport means for transporting the capacitor, at least one initial charging stage and a measurement stage are sequentially arranged at intervals,
The step of alternately charging the capacitor and interrupting charging at least once is performed using the initial charging stage,
The step of charging the main capacitance of the capacitor immediately before discharging the capacitor for the predetermined period and the step of measuring the leakage current flowing through the insulation resistance are performed using the measurement stage,
In the measurement stage, a discharge period from charging the main capacitance of the capacitor to measuring a leakage current flowing through the insulation resistance is set to the predetermined period,
At least the measurement stage is provided with energization means capable of switching between energization and deenergization of the capacitor,
In the measurement stage, the capacitor is charged in a state where the electrode of the capacitor is energized by the energization means, and the predetermined timing is adjusted by adjusting a timing at which the energization of the capacitor electrode is interrupted by the energization means. 6. The capacitor leakage current measuring method according to claim 5, wherein a period is adjusted, and a leakage current flowing through the insulation resistance is measured after elapse of the predetermined period. In a leakage current measuring device that measures a leakage current by applying a DC voltage to a capacitor to be measured,
Charging means for charging the capacitor, including a dielectric absorption factor inside the capacitor;
Discharging means for discharging the charge accumulated in the capacitor through an insulation resistance inside the capacitor for a predetermined period until the potential difference between both ends of the capacitor after charging becomes equal to the potential difference between both ends of the capacitor at the time of leakage current measurement; ,
A leakage current measuring means for measuring a leakage current flowing through the insulation resistance after the predetermined period,
The charging means has a first current limiting circuit connected in series to the capacitor,
The measuring means has a second current limiting circuit connected in series to the capacitor,
The impedance at the completion of charging of the first current limiting circuit is set smaller than the impedance of the second current limiting circuit ,
The capacitor leakage current measuring device, wherein the potential difference between both ends of the capacitor at the time of measuring the leakage current is a voltage at which a charging current does not flow through the capacitor when a probe for measuring leakage current is connected to the capacitor.   The predetermined period is optimized based on the capacitance of the capacitor, the impedance when the charging of the first current limiting circuit is completed, and the impedance of the second current limiting circuit when measuring the leakage current. 9. The capacitor leakage current measuring apparatus according to claim 8, wherein   Assuming that the predetermined period is t, the main capacitance of the capacitor is C, the impedance at the completion of charging of the first current limiting circuit is R2, and the impedance of the second current limiting circuit is R3, t = C (R3− 10. The capacitor leakage current measuring device according to claim 9, wherein the predetermined period is optimized so that R2) holds.   9. The charging unit according to claim 8, further comprising an initial charging unit that alternately charges and charges the capacitor at least once until a dielectric absorption current does not flow through the dielectric absorption factor of the capacitor. The capacitor | condenser leakage current measuring apparatus in any one of thru | or 10. 12. The capacitor leakage current measuring device according to claim 11, wherein the charging unit includes a pre-measurement charging unit that charges a main capacity of the capacitor immediately before the capacitor is discharged for the predetermined period . Along the transport path of the transport means for transporting the capacitor, at least one initial charging stage, a pre-measurement charging stage, and a measurement stage are sequentially arranged at intervals,
The initial charging means alternately performs charging and interruption of the capacitor at least once using the initial charging stage,
The pre-measurement charging means charges the main capacity of the capacitor immediately before discharging the capacitor for the predetermined period using the pre-measurement charging stage,
The leakage current measuring means measures a leakage current flowing through the insulation resistance using the measurement stage,
The capacitor leakage current measuring device according to claim 12, wherein a discharge period between the pre-measurement charging stage and the measurement stage is set to the predetermined period. Along the transport path of the transport means for transporting the capacitor, at least one initial charging stage and a measurement stage are sequentially arranged at intervals,
The initial charging means alternately performs charging and interruption of the capacitor at least once using the initial charging stage,
The pre-measurement charging unit charges the main capacity of the capacitor using the measurement stage, and the leakage current measurement unit flows to the insulation resistance after discharging the capacitor for the predetermined period using the measurement stage. Measure the leakage current,
In the measurement stage, a discharge period from charging the main capacitance of the capacitor to measuring a leakage current flowing through the insulation resistance is set to the predetermined period,
At least the measurement stage further includes energization means capable of switching energization and deenergization to the capacitor,
In the measurement stage, the capacitor is charged in a state where the electrode of the capacitor is energized by the energization means, and the predetermined timing is adjusted by adjusting a timing at which the energization of the capacitor electrode is interrupted by the energization means. 13. The capacitor leakage current measuring device according to claim 12, wherein a period is adjusted and a leakage current flowing through the insulation resistance is measured after elapse of the predetermined period.

Images