JP5382286B2 - Insulation resistance measurement circuit - Google Patents

Description

  The present invention relates to an insulation resistance measurement circuit, and more particularly to an insulation resistance measurement circuit that detects a connection failure when measuring an insulation resistance of a measurement object having a capacitance value such as a capacitor.

  In general, the measurement of the insulation resistance of a capacitor is performed by applying a measurement voltage to the capacitor to be measured and measuring the voltage or current of the capacitor after being sufficiently charged. However, since the insulation resistance value of the capacitor is high, even when the measurement terminal is not sufficiently in contact with the electrode of the capacitor, the determination may be made in the same manner as when a good capacitor is measured. In order to avoid such problems, various patent literatures have examined methods for measuring the insulation resistance of capacitors.

Japanese Unexamined Patent Publication No. 3-77073

Hereinafter, a conventional insulation resistance measuring circuit will be described. In the conventional insulation resistance measurement, as shown in FIG. 5, the voltage of the voltage source 1 is applied to the measurement object 3 and the current IL is measured by the ammeter 2. Then, the insulation resistance RL is
RL = V1 / A1
Is required.

Thus, in the insulation resistance measurement circuit of FIG. 5, the insulation resistance is measured using the voltage source 1 and the ammeter 2.

By the way, when the insulation resistance is measured in a state where the measurement terminal of the insulation resistance meter and the measurement target are not correctly connected, the measurement value is generally an overrange or high resistance measurement value. Therefore, if the resistance value to be measured is sufficiently low, the connection failure can be determined from the measured resistance value.

However, when measuring a measurement target having a high insulation resistance such as a capacitor, it is not possible to determine a connection failure from the measured insulation resistance value. For this reason, when a connection failure occurs, the defective product may be determined as a non-defective product.

In particular, in an automatic inspection apparatus or the like that is inspected at high speed, there is a high possibility that a connection failure will occur. Therefore, it is necessary to check whether the insulation resistance is measured in a correctly connected state.

  The present invention has been made in view of these problems, and an object of the present invention is to provide an insulation resistance measurement circuit that detects a connection failure when measuring an insulation resistance of a measurement object having a capacitance value such as a capacitor. And

In order to achieve such a problem, the invention described in claim 1
In an insulation resistance measurement circuit having an insulation resistance measurement block for measuring an insulation resistance of a measurement object having a capacitance value,
A current source for supplying current to the measurement object;
A comparator that outputs a signal to that effect when there is a connection failure by comparing the voltage of the measurement target when a current is supplied to the measurement target for a predetermined time with this current source,
A switch for connecting the insulation resistance measurement block and the measurement object;
This switch discharges the electric charge charged in the measurement object when measuring the insulation resistance value while the measurement object is charged, or after completing the insulation resistance measurement of the load capacity of the measurement object having a capacitance value. In this case, the insulation resistance measurement block and the measurement object are connected to discharge the charge charged in the measurement object.

Further, the invention according to claim 2 is the insulation resistance measuring circuit according to claim 1,
The reference value that the comparator compares with the voltage to be measured is:
(Charging time of measurement target * Current value of current output from current source) / (Floating capacitance of measurement target + Load capacity of measurement target) <Reference value <(Charging time of measurement target * Output from current source) Current value) / stray capacitance to be measured
It is determined by the relationship.

Furthermore, the invention according to claim 3
In an insulation resistance measurement circuit having an insulation resistance measurement block for measuring an insulation resistance of a measurement object having a capacitance value,
A current source for supplying current to the measurement object;
A voltmeter to measure the voltage across this current source;
A switch for connecting the insulation resistance measurement block and the measurement object;
The stray capacitance CO before the measurement object is connected and the load capacitance CL in a state where the measurement object is connected are obtained by the following conversion formula.
CO = (T1 × IS) / (VM1−VM0)
CL = {(T1 × IS) / (VM1-VM0)}-CO
T1: Current + IS generation time
IS: Current generated by current source 40
VM0: Current + value measured by voltmeter 70 before IS
VM1: Measured by voltmeter 70 when current + current after IS is 0

The present invention has the following effects. According to claim 1, there is a connection failure by comparing a current source for supplying a current to the measurement target and a voltage of the measurement target when the current is supplied to the measurement target for a predetermined time by the current source with a reference value. In some cases, a comparator that outputs a signal to that effect is provided, so that it is possible to provide an insulation resistance measurement circuit that detects a connection failure when measuring the insulation resistance of a measurement object having a capacitance value such as a capacitor. .
According to the third aspect, since the voltmeter 70 is provided instead of the comparator 50 of the first aspect, the capacitance value inspection can be performed simultaneously with the connection failure.

Hereinafter, a configuration example of the insulation resistance measurement circuit of the present invention will be described with reference to FIG. The voltage source 10 applies a voltage to the measurement object 60 and is used for measuring the insulation resistance. The ammeter 20 is connected to the voltage source 10 in series and is used for measuring the insulation resistance. The switch 30 connects the voltage source 10 and the ammeter 20 to the measurement target 60 in the on state. The current source 40 is used for measuring the capacity of the measurement target 60. The comparator 50 compares the output voltage Vo with the comparison voltage source Vref. The measurement object 60 has a capacitance value such as a capacitor.

Next, the operation of FIG. 1 will be described with reference to FIG. 2 is a timing chart of FIG. 1, (A) is a timing chart of the current source 40, and (B) is a timing chart of the output voltage Vo. The capacitance value to be measured is detected by the following procedure before or after the insulation resistance measurement, and if there is a defect, a connection failure detection signal is generated from the comparator 50. First, set Vref as follows.

Here, CO is a stray capacitance to be measured, CL is a load capacitance of the measurement target 60, and IS is a current output from the current source 40. Subsequently, the switch 30 is turned on, the voltage source 10 is set to 0 V, and the charge charged in the measurement target 60 is sufficiently discharged. Note that this operation is not necessary when the measurement target 60 is not charged.

The switch 30 is turned off, and the insulation resistance measurement block (the voltage source 10 and the ammeter 20) is disconnected. A current (+ IS) is generated from the current source 40 for a period of time T1 (reference numeral 100 in FIG. 2A). Here, if connected correctly, the output voltage Vo is

Thus, Vref is not exceeded and an abnormality detection signal is not output (FIG. 2 (B), solid line of output voltage Vo). However, if a connection failure occurs, the output voltage Vo is

Since Vref is exceeded ( FIG. 2B , broken line of the output voltage Vo), an abnormality detection signal is output from the comparator 50. Finally, a current (-IS) is generated from the current source 40 for a period of time T1 (reference numeral 110 in FIG. 2A), and the charge charged in the measurement target 60 is discharged. Alternatively, the voltage source 10 is set to 0 V, the switch 30 is closed, and the charge charged in the measurement target 60 is discharged.

As described above, when a connection failure detection signal is output from the comparator 50, an alarm is sounded or a lamp (not shown) is turned on to detect a connection failure and the insulation resistance test is executed again. Misjudgment is prevented by putting it on hold as a defect.

Next, an application example of the present invention will be described with reference to FIG. 3, but the same components as those in FIG. In the configuration of FIG. 3, a voltmeter 70 is provided instead of the comparator 50 of FIG.

  As shown in FIG. 3, a voltmeter 70 that measures the voltage across the current source 40 is connected in parallel. Before or after the insulation resistance measurement, the stray capacitance CO and the load capacitance CL of the measurement object 60 are measured by the following procedure. First, the current generated by the current source 40 is set to 0 A, and the output voltage Vo at this time is measured by the voltmeter 70 to be VM0.

A current (+ IS) is generated from the current source 40 for a period of time T1 (reference numeral 120 in FIG. 4A).
The generated voltage IS of the current source 40 is set to 0A, and the output voltage Vo at this time is measured by the voltmeter 70 and is set as VM1 (reference numeral 140 in FIG. 4B). The stray capacitance CO and the load capacitance CL are obtained by the following conversion formula. The stray capacitance CO is obtained before connecting the measuring object 60, and the load capacitance CL is obtained with the measuring object 60 connected.

・・・（４）

... (4)

・・・（５）

... (5)

Finally, a current (-IS) is generated from the current source 40 for a period of time T1 (reference numeral 130 in FIG. 4A), and the charge charged in the measurement target 60 is discharged. Alternatively, the voltage source 10 is set to 0 V, the switch 30 is closed, and the charge charged in the measurement target 60 is discharged. In this way, the capacitance value of the load capacitance CL is measured. When a connection failure occurs, the capacitance between Hi and Lo becomes only CO, and the connection failure can be detected from the measured value of CL.

  Thus, since the voltmeter 70 is provided instead of the comparator 50, the capacitance value inspection can be performed simultaneously with the connection failure.

It is an example of a structure of the insulation resistance measuring circuit of this invention. FIG. 2 is a timing diagram of FIG. 1. It is a block diagram of the application example of this invention. FIG. 4 is a timing diagram of FIG. 3. It is an example of a structure of the insulation resistance measuring circuit by a prior art.

Explanation of symbols

10 Insulation Resistance Measurement Voltage Source 20 Insulation Resistance Ammeter 30 Switch 40 Capacity Measurement Current Source 50 Comparator 60 Measurement Object 70 Voltmeter

Claims (3)

In an insulation resistance measurement circuit having an insulation resistance measurement block for measuring an insulation resistance of a measurement object having a capacitance value,
A current source for supplying current to the measurement object;
A comparator that outputs a signal to that effect when there is a connection failure by comparing the voltage of the measurement target when a current is supplied to the measurement target for a predetermined time with this current source,
A switch for connecting the insulation resistance measurement block and the measurement object;
This switch discharges the electric charge charged in the measurement object when measuring the insulation resistance value while the measurement object is charged, or after completing the insulation resistance measurement of the load capacity of the measurement object having a capacitance value. An insulation resistance measurement circuit , wherein the insulation resistance measurement block and the measurement object are connected to discharge the charge charged in the measurement object. The reference value that the comparator compares with the voltage to be measured is:
(Charging time of measurement target * Current value of current output from current source) / (Floating capacitance of measurement target + Load capacity of measurement target) <Reference value <(Charging time of measurement target * Output from current source) 2. The insulation resistance measuring circuit according to claim 1, wherein the insulating resistance measuring circuit is determined by a relationship of current value of current to be measured) / stray capacitance to be measured. In an insulation resistance measurement circuit having an insulation resistance measurement block for measuring an insulation resistance of a measurement object having a capacitance value,
A current source for supplying current to the measurement object;
A voltmeter to measure the voltage across this current source;
A switch for connecting the insulation resistance measurement block and the measurement object;
An insulation resistance measurement circuit, wherein a stray capacitance CO before connecting the measurement object and a load capacitance CL in a state where the measurement object is connected are obtained by the following conversion formula.
CO = (T1 × IS) / (VM1−VM0)
CL = {(T1 × IS) / (VM1-VM0)}-CO
T1: Current + IS generation time
IS: Current generated by current source 40
VM0: Current + value measured by voltmeter 70 before IS
VM1: Measured by voltmeter 70 when current + current after IS is 0

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