JP2006226917A - Withstand voltage testing instrument and disconnection detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate failure, after starting an electric power supply unit, caused by stresses in withstand voltage tests. <P>SOLUTION: This instrument is constituted of a disconnection detector, having a detecting part attached to a probe of a withstand voltage testing instrument and for detecting the change in the current flowing in the probe, a filter part for extracting a prescribed frequency range of signal from an output of the detecting part, a comparison part for detecting and holding abnormal value by comparing a filter output with a prescribed value, and a display part for executing display in accordance with the conditions of the comparison part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for inspecting withstand voltage resistance of a power supply unit of an electric device.

  It is necessary to test the pressure resistance (insulating properties) of the manufactured electrical equipment (particularly the power supply unit). Electronic devices used by general users such as personal computers usually use a commercial power supply of 100 VAC (primary side), and electronic circuits use a low voltage such as 5 VDC (secondary side). Touching the high voltage on the primary side may cause an electric shock, so make sure that this voltage does not leak to the secondary side. That is, it is necessary to confirm that insulation is secured by applying a high voltage between the primary and secondary.

  A normal withstand voltage tester is a pair of probes each provided with a connector (connector, clip, etc.) at the end, which can be connected to the primary and secondary test terminals of the electrical equipment, and the other end of both probes. A high-voltage power supply unit that outputs a high voltage connected to the current detection unit, a current detection unit that detects a leakage current flowing between both test terminals, a display unit that displays a detected current value or anomaly detection, and a high-voltage power supply unit A control unit that controls display of the output voltage and the current value by the display unit is provided.

  FIG. 1 shows a state when a withstand voltage test of an electric device is performed using a withstand voltage tester. First, both probes are respectively connected to a pair of test terminals in the electrical equipment. In the figure, the probe 3a of the withstand voltage tester 2 is connected to the primary side input terminal of the power supply unit 1 to be tested, and the other probe 3b is connected to the secondary side output terminal.

  Next, a high voltage for a withstand voltage test is output from the power supply unit of the withstand voltage tester. A current flowing between both test terminals is detected when a voltage for withstand voltage test is applied to both test terminals via both probes. Leakage current flows when insulation is poor. The current value detected by the current detection unit is displayed on the display unit. Alternatively, when it is determined that the leakage current is a predetermined value or more, a lamp display or the like is performed as an alarm.

  The person in charge of the test (or automatic determination device) determines that the electrical device to be tested is a pass product when the displayed current value is below a predetermined threshold value or when no alarm is activated, and the current value is a threshold value. If it exceeds the limit or there is an alarm, it will be judged as a rejected product.

  However, the probe may be disconnected due to deterioration of the contact point or cable due to bending stress or aging of the cable during use. In that case, since no voltage is applied to both test terminals of the electrical equipment, no current flows, and those that are originally rejected are also determined to be acceptable.

As a technique for solving this problem, a technique of a withstand voltage tester capable of performing a disconnection check (disconnection inspection) of a probe (line) is disclosed. As a result, a complete disconnection can be detected.
However, although there is no problem in use conditions (excessive load, temperature abnormality, etc.), there is no problem in the power supply unit that has no problem at the time of inspection and no problem in the initial operation. It may become defective after a few months of operation. As a result of investigating the cause, it was found that there was a factor that applied stress to the object to be inspected during the dielectric strength test, which was caused by the disconnection / contact failure of the probe.

  This is to detect the application of stress by the withstand voltage test as described above to prevent a field failure of the power supply unit.

  Usually, the applied voltage in the withstand voltage test is about 1500 V, and the frequency is 50 Hz to 60 Hz, which is the same as the commercial power supply.

  As shown in FIG. 1, one end of the probe is connected in a state where the primary input terminal to be tested is short-circuited, and the other end of the probe is connected in a state where the secondary output terminal to be tested is short-circuited. Therefore, even if a high voltage is applied during this period, it is applied only to the primary / secondary insulating parts of the transformer of the power supply unit, and does not apply to circuit components such as diodes.

  The stress application mechanism due to abnormality during the pressure test is as follows.

  Long-term use or operation errors can cause the probe wiring to break or poor connector contact. Then, during the test, a discharge occurs at the disconnection portion or the contact failure portion, and a high-frequency (about several kHz) voltage change occurs. Then, a high voltage is applied to the component instantaneously through the coupling capacitance and stray capacitance of the transformer and circuit. FIG. 2 (a) shows a waveform applied between probes at such a time. FIG. 2B is an example of a voltage waveform applied to the secondary-side diode 4. In this way, stress is applied, and even if it is not destroyed on the spot, it is deteriorated and easily broken.

  The conventional withstand voltage tester monitors the leakage current and determines that it is abnormal when it exceeds a predetermined value. However, when the wire breaks or the contact is poor, the instantaneous leakage current increases but the average current does not change so much. Therefore, the detection function of the conventional pressure tester does not operate.

  FIG. 3 shows a leakage current waveform when the withstand voltage test is abnormal. According to this, the value of the peak current of the leakage current waveform at the time of abnormality has a large variation, while the generation of the high-frequency current has a small variation. That is, it has been found that an abnormality can be detected if a high-frequency current is detected by an electric circuit.

  Therefore, a detection unit that is attached to the probe of the withstand voltage tester and detects a change in the current flowing through the probe, a filter unit that extracts a signal in a predetermined frequency range from the output of the detection unit, and an abnormality caused by comparing the filter output with a predetermined value It is configured as a disconnection detector having a comparison unit that detects and holds a value and a display unit that performs display according to the state of the comparison unit. Further, when the comparison unit detects a voltage equal to or higher than a predetermined value, it is configured to have a recording unit that records the detection result, so that the occurrence of an abnormality is reliably caught.

  By reliably detecting that a stress has been applied to the test target device during the pressure resistance test, it is possible to eliminate power failure after operation.

Example 1
FIG. 4 shows a configuration example of a withstand voltage test apparatus to which a disconnection detector is added. This figure shows a configuration in which a disconnection detector is added to a probe of a conventional pressure tester. Of course, you may comprise as a pressure | voltage resistant test apparatus provided with the disconnection detector.

  The disconnection detector has a detection unit 11 that captures a change in the current flowing through the probe 3a of the withstand voltage tester, a filter that extracts a signal of about 1 kHz from its output, and a filter unit 12 that has a circuit for adjusting the level. A comparison unit 13 that holds when the threshold value is larger than the threshold value and a display unit 14 that displays or records the result are provided.

  FIG. 5 shows a circuit configuration example of the disconnection detector.

  The detection unit 11 only needs to be capable of detecting a change in current of about several kHz flowing through the probe. The filter unit 12 is a circuit that removes commercial frequencies and noise components and adjusts the detection level. The comparator 13 is a circuit that amplifies the signal and holds it when an abnormal value is detected by comparison with a predetermined value. When an abnormal value is detected, it is displayed by the light emitting diode of the comparison unit. Since an abnormal value is detected, it is retained, so that the display by the light emitting diode is retained unless reset by a reset switch. Accordingly, it is possible to detect a temporary abnormality such as an operation error or deterioration of the test apparatus (probe connector) without overlooking it.

  It is also easy to configure the automatic test apparatus including the pressure resistance test as a part of the apparatus for recording the test result so as to record the occurrence of the disconnection state.

It is a figure which shows a prior art example. These are the applied waveform of the withstand voltage test and the abnormal voltage waveform applied to the part. It is a leakage current waveform at the time of abnormality. It is a block diagram of the pressure | voltage resistant test apparatus which added the disconnection detector. It is an example of a circuit of a disconnection detector.

Explanation of symbols

1 Equipment to be tested (power circuit)
2 Voltage tester 3a Probe 3b Probe 4 Diode 10 Disconnection detector 11 Detection unit 12 Filter unit 13 Comparison unit 14 Display unit

Claims (3)

A detector that is attached to the probe of the pressure tester and detects a change in current flowing through the probe;
A filter unit for extracting a signal in a predetermined frequency range from the output of the detection unit;
A comparison unit that detects and holds an abnormal value by comparing the filter output with a predetermined value;
The disconnection detector which has a display part which displays according to the state of a comparison part. The disconnection detector according to claim 1,
A disconnection detector, comprising: a recording unit that records a detection result when the comparison unit detects a voltage of a predetermined value or more.   A pressure tester provided with the disconnection detector according to claim 1 or 2 on a probe.

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