JPH11231014A - Withstand voltage tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily discriminate a partial discharge phenomenon generated at an abnormal part by applying adequate voltage to a tested object. SOLUTION: Voltage is applied to a tested object through a single-phase variable transformer, a boost transformer, a charge-discharge current limiting circuit and a discharge detecting part. In the case of a coil of the tested object is damaged and brought into contact with a core, upon detecting the flow of a relatively large current to the discharge detecting part without generating partial discharge, voltage applied to the tested object is cut off. In the case of the coil of the tested object being in contact with the core without being damaged, partial discharge is generated at a contact part, and a micro partial discharge current flows to the discharge detecting part. This current and a signal of a noise detecting part are amplified by a differential amplifying part, and a partial discharge signal is extracted. Since the charge-discharge cycle of partial discharge is within a fixed range, abnormality of the tested object can be discriminated by measuring the partial discharge signal through a band- pass filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a withstand voltage evaluation tester for detecting a withstand voltage between a motor, a transformer, and a choke coil with respect to ground and between layers.

[0002]

2. Description of the Related Art A conventional withstand voltage tester is a method for examining abnormalities when a constant voltage is applied for a fixed time in accordance with JIS, and a current value not more than a current value depending on a ground-to-ground or interlayer capacitance of a DUT. If it was, it was determined that there was no abnormality.

[0003] However, the performance and quality of the electric wire used for the winding are improved, and even if the core and the electric wire or the electric wire between different poles are in contact with each other, if the electric wire is not damaged, the abnormality judgment may not be performed. Was.

Attempts have also been made to detect abnormalities due to the partial discharge phenomenon, but the partial discharge current is extremely small, making measurement difficult due to the influence of power line noise and external noise.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a withstand voltage tester for detecting an abnormality which cannot be found by a conventional withstand voltage tester without destroying a device under test.

The withstand voltage tester of the present invention suppresses external noise and power supply noise by using a noise detection circuit and a differential amplifier for an extremely small partial discharge current, and provides a partial discharge cycle to a device under test and a current suppression circuit. By combining this with the voltage supply side of the DUT and a bandpass filter that matches the discharge cycle, it is possible to easily determine the partial discharge phenomenon that occurs in the abnormal part of the DUT.

[0007]

Embodiments of the present invention will be described below.
FIG. 1 shows an embodiment of a withstand voltage tester. In FIG. 2, a voltage is applied to the device under test through a single-phase variable transformer 1, a step-up transformer 2, a charge / discharge current limiting circuit 3, and a discharge detection unit 4. The winding HA of the DUT is damaged and the core HB
When it is detected that a relatively large current flows through the discharge detection unit without detecting partial discharge, the voltage applied to the DUT is cut off. When the winding HA and the core HB are in contact with each other without any damage to the winding of the DUT, a partial discharge occurs at the contact portion, and a small partial discharge current flows through the discharge detection unit 4. This current and the noise detection unit 5 is amplified by the differential amplifying unit 6 to extract a partial discharge signal. Further, the charge / discharge cycle of the partial discharge is performed by the charge / discharge current limiting circuit 3 within a certain range. Is measured through the band pass filter 7, the abnormality of the test object can be determined. On the other hand, when the winding HA of the DUT is not in contact with the core HB, partial discharge does not occur, and only a current of almost the same noise component flows through the discharge detection unit and the noise detection unit to the output of the differential amplifier. Since no discharge detection signal is detected, no abnormality is determined.

[Selection diagram] Fig. 1

[0008]

As described above, according to the present invention, by applying an appropriate voltage to the DUT, there is no damage to the windings of the DUT, and the conventional withstand voltage tester does not. It is possible to determine an abnormality that cannot be found. In addition, by suppressing the current supplied to the DUT, destruction of the DUT can be prevented.

Claims (1)

[Claims] When a partial discharge occurs in the DUT, a discharge current limiting circuit that limits charging and discharging, a discharge detection unit that detects the partial discharge of the DUT, a noise detection unit that detects common noise, and noise components are removed. A withstand voltage tester with an operational amplifier that amplifies a specific frequency band.