JPH02119216A - Method for testing capacitor - Google Patents

Abstract

PURPOSE:To judge a defective article which is short-circuited in a very short time as defective by judging such capacitor to be good in the case where voltage between terminals of the capacitor monotorously increases with time when the capacitor is charged with a dc power supply and a resistor connected in series. CONSTITUTION:A dc power supply 1 and a resistor 3 are connected in series with a capacitor 5 to be tested, voltage between terminals of the capacitor is detected with the capacitor charged with electricity, and the capacitor is judged to be good with a maximum voltage holding circuit 8 for holding the maximum value and a comparator 9 if the voltage between terminals of the capacitor 5 increases with time, the variation being expressed by a monoton increasing function. For example, the maximum voltage holding circuit 8 holds the maximum value of the voltage applied to the capacitor 5 to be tested and the comparator 9 compared the voltage being applied to the capacitor 5 with the maximum voltage that has ever been applied and generates output if the voltage applied to the capacitor 5 has dropped. Then, an OR circuit 13 outputs logical sum of output of a comparator 4 for detecting a shorted circuit and output of the comparator 9, to judge whether or not the capacitor 5 is short-circuited.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for testing capacitors,
In particular, the present invention relates to a test method for selecting insulation-defective products that instantaneously cause a short circuit.

[Prior art] A test to measure the insulation resistance of a capacitor and remove defective products is carried out by:
6 and a direct voltage type #17 are connected in series, and the voltage across the resistor 16 is compared with a reference voltage source 18 by a comparator 20. 19 is a switch. Here, the voltage of the DC power supply 17, the resistance value of the resistor 16, and the voltage of the reference voltage source 18 need to be adjusted using the capacitor 15 under test.

Furthermore, it is necessary to distinguish the charging current flowing through the capacitor 15 under test from a short-circuit current due to poor insulation.

Problems to be Solved by the Invention As mentioned above, in the test method shown in FIG. Varies in size and duration. Therefore, during charging, it is extremely difficult to distinguish between this charging current and short-circuit current due to instantaneous insulation failure.

In addition, it is known that when the cause of insulation failure is conductive particles, the time for the short current to flow is very short, and conventional insulation testing methods do not allow insulation failure due to conductive particles. It was almost impossible to determine that the capacitor in question was defective.

Means for Solving the Problems In order to solve the above problems, the present invention connects a DC power supply and a resistor in series to a capacitor under test, and when the capacitor is charged, detects the voltage between the terminals of the capacitor. This capacitor testing method is characterized by a maximum voltage holding circuit that holds the maximum value, and a comparator that determines that the capacitor is non-defective when the voltage between the terminals of the capacitor draws a simple increasing curve that increases over time.

Therefore, in other cases, the product can be determined to be defective even if it is within the standard value and determined to be non-defective by the conventional short-circuit current measurement method.

If the capacitor under test is momentarily short-circuited due to conductive particles or the like, the capacitor under test enters a discharge state and the voltage between the terminals of the capacitor under test temporarily decreases.

In other words, it is not a simple increasing curve. Therefore, by comparing the maximum voltage held with the voltage across the terminals of the test capacitor at the moment of short-circuiting, it is possible to eliminate such defective capacitors that momentarily become short-circuited.

Embodiment FIG. 1 shows an embodiment of the present invention. 1 is a DC power supply,
2 is a short-circuit current detection resistor. 3 is a short-circuit current limiting resistor, and 4 is a comparator for short-circuit detection.

5 is a test capacitor, and 6 and 7 are voltage dividing resistors.

8 is a maximum voltage holding circuit, which holds the maximum value of the voltage applied to the capacitor 5 under test.

9 is a comparator, which compares the voltage applied to the test capacitor 5 with the maximum voltage applied up to that point, and outputs an output when the voltage applied to the test capacitor 5 decreases;
The test capacitor 5 is determined to be defective.

13 is an OR circuit that outputs the OR of the output of the comparator 4 and the output of the comparator 9, and determines whether or not the capacitor 5 under test has a short-circuit defect. 14 is a reference voltage source.

10 is a measurement start switch 7, which interlocks switches 11 and 12. When switch 10 opens,
By closing the switch 11, the maximum voltage holding circuit 8
Reset. Further, when the switch 10 is opened, the switch 12 is closed, thereby discharging the capacitor 5 under test.

Effects of the Invention By adding the maximum voltage holding circuit 8 and the comparator 9 as in the embodiment shown in FIG. A defective product that causes a short-term short circuit can be determined to be a short-circuit defect.

As described above, the present invention is a very effective method for testing capacitor elements and finished products.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of a capacitor test circuit according to the present invention, and FIG. 2 is a diagram of a conventional capacitor test circuit. 1: DC power supply 2 Rainbow iodine current detection resistor 3 Rainbow iodine current limiting resistor 4 Rainbow iodine detection comparator 5: Test capacitor 8: Maximum voltage holding circuit 9: Comparator for patent ■Ryojin Nichicon Co., Ltd.

Claims (1)

[Claims] Connect a DC power supply and a resistor in series to the capacitor under test,
A maximum voltage holding circuit that charges the capacitor, detects the voltage between the terminals of the capacitor, and holds the maximum value, and a comparator that determines a good product when the voltage between the terminals of the capacitor draws a simple increasing curve that increases over time. A capacitor testing method characterized by determining.