JPH08136609A - Withstand voltage testing device - Google Patents

Abstract

PURPOSE: To detect a corona voltage with a sufficiently large amplitude. CONSTITUTION: In a withstand voltage testing device which detects a corona voltage generated from an object 4 to be tested by applying a voltage to the object 4 from a testing power source 1, an inductor 3 is connected in series between the power source 1 and object 4. In addition, a capacitor is connected in series with the inductor 3 so as to change the resonance frequency of a serial resonance circuit composed of the inductor 3 and capacitor to a testing frequency. Since the inductor 3 enlarges the sporadically generated corona voltage, the voltage can be detected with high sensitivity and, since the resonance frequency of the serial resonance circuit composed of the inductor 3 and capacitor is changed to the testing frequency, the impedance of the testing frequency can be reduced to about zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a withstand voltage tester for testing withstand voltage of transformers, choke coils, insulated wires and the like.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a circuit configuration of a conventional interlayer withstand voltage test apparatus. Conventionally, when testing an interlayer withstand voltage using a transformer, a choke coil or the like as a device under test, a high voltage is applied between layers of the device under test S from a high voltage output transformer T as shown in FIG. The corona voltage is detected by the corona voltmeter V through the high-pass filter F. For example, considering the mechanism in which the layers of the device under test S are flashed over to reach a completely short-circuited state, as a model of the insulator, as shown in FIG. 2, a plurality of capacitors C _{1 to} C _n having a minute gap between the layers are formed. It consists of a series connection circuit. Therefore, when a high voltage is applied to both ends of the capacitors, corona sporadicly occurs when one or more of the capacitors connected in series have a poor withstand voltage, and when all of the capacitors have a poor withstand voltage, a flashover occurs. Poor pressure resistance. As described above, the corona is generated at a voltage before the insulator of the device under test S is flashed over and becomes a completely short-circuited state, and is a sign that a withstand voltage failure occurs. Therefore, in the interlayer withstand voltage test, It is important to reliably detect the occurrence of this corona.

[0003]

However, in the conventional withstanding voltage test apparatus, since the output impedance of the high voltage output transformer T is high in the frequency band in which corona occurs, the corona voltage is not attenuated so much and no problem occurs. There is a problem of poor sensitivity.

The present invention solves the above problems and provides a withstand voltage test apparatus capable of detecting a corona voltage with a sufficiently large amplitude even if a minute corona is generated. It is intended.

[0005]

To this end, the present invention provides a withstand voltage test apparatus for applying a voltage from a test power supply to a device under test to detect a corona voltage generated in the device under test. It is characterized in that an inductor is inserted and connected in series between and, and further, a capacitor is connected in series with the inductor and the resonance frequency of the series resonance circuit of the inductor and the capacitor is set to the test frequency. is there.

[0006]

In the withstand voltage test apparatus of the present invention, since the inductor is inserted and connected in series between the test power supply and the device under test, sporadic corona voltage can be detected with high sensitivity. Further, since the resonance frequency of the series resonance circuit of the inductor and the capacitor is set to the test frequency by connecting the capacitor in series with the inductor, the impedance at the test frequency can be brought close to zero.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a withstand voltage test apparatus according to the present invention, FIG. 2 is a diagram showing a model circuit for explaining corona generation, and FIG. 3 is a model circuit for explaining detection of corona voltage. FIG. 2 is a diagram showing a test power source, 2
Is a high voltage output transformer, 3 is an inductor, 4 is a device under test,
5 is a high-pass filter, 6 is a corona voltmeter, E is a test power supply, L is an inductor, C1 to Cn are insulators, SW is a switch, and V is a peak detection voltmeter.

In FIG. 1, a high voltage output transformer 2 boosts the voltage of a test power supply 1 of, for example, about 10 V to 1000 V and outputs the voltage, which is applied to a device under test 4 through an inductor 3. The device under test 4 is a transformer, a choke coil, an insulated wire, or the like, and the high voltage output of the high voltage output transformer 2 is applied between the conductors or between the conductor and the insulator. The high-pass filter 5 is connected between the power supply lines that apply a high-voltage output to the DUT 4 through the inductor 3, blocks the test frequency band supplied by the test power supply 1, and causes the frequency band of the corona voltage generated in the DUT 4. The corona voltage generated in the DUT 4 is taken into the corona voltmeter 6 through the high pass filter 5. The corona voltmeter 6 is preferably, for example, a peak value detection type, but it goes without saying that it may be another type.

Next, the detection of the corona voltage by the withstand voltage test device constructed as described above will be explained. For example, when a high voltage output is applied to the insulator by the withstand voltage test apparatus according to the present invention, it can be represented by a series connection circuit of a plurality of capacitors having a minute gap as shown by the insulators C1 to Cn in FIG. Corona generation is a state in which one or a plurality of withstand voltage defects of the insulators C1 to Cn are sporadically generated over time.
If all of ~ Cn are defective in breakdown voltage, a flashover occurs and the breakdown voltage is completely defective. Therefore, these insulators C1
As shown in FIG. 3, the occurrence of corona due to the breakdown voltage failure in Cn to Cn is short-circuited (ON) to switch SW, and switch S
The withstand voltage test apparatus according to the present invention is configured so that both ends of W are detected by the peak detection voltmeter V. In the model circuit shown in FIG. 3, since the switch SW is short-circuited when a corona occurs, it closes sporadically and immediately returns. At this time, both ends of the switch SW cause a transient phenomenon due to the inductor L connected in series to the test power supply E, and have a much higher voltage than in the case where a resistor is connected instead of the inductor L, for example. , The voltage is detected by the peak detection voltmeter V. Further, as a matter of course, since the impedance higher than the output impedance of the high voltage output transformer is obtained by connecting the inductor L, the load drop of the corona voltage is reduced.

In the withstanding voltage test device, a withstand voltage test for checking the dielectric strength of the primary winding vs. the secondary winding of the transformer and a short-circuit state between the windings of the covered electric wire used for the primary winding and the secondary winding Then, an inter-layer withstand voltage test is conducted. For example, when winding 1000 turns as a winding, 100 turns, the interlayer paper is wound on it, and then 100 turns, so that the potential difference per turn is small, so there is no problem. A 100-fold potential difference will occur between the layers. Usually, a defect is a withstand voltage defect in such a portion, and is called an interlayer withstand voltage because of its origin. Therefore, in this case, even if the interlayer withstand voltage defect occurs on the secondary side, the primary winding and the secondary winding are electromagnetically coupled, and therefore the pass / fail judgment can be made only by the primary side test. It will be possible. Further, for example, in a test of a transformer having a primary rating of 10V and a secondary rating of 1000V, a high voltage transformer is not required.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the above embodiment, the high voltage output of the high voltage output transformer was applied to the device under test through the inductor, but a capacitor may be connected in series to the inductor. FIG. 4 is a diagram showing another embodiment of the withstand voltage test apparatus according to the present invention, and 7 shows a capacitor forming a resonance circuit with the inductor 3. In the withstand voltage test apparatus shown in FIG. 1, the load drop of the applied voltage may not be negligible depending on the value of the inductor 3. In that case, by forming a series resonance circuit with the inductor 3 by the capacitor 7 as shown in FIG.
The impedance can be brought close to zero at the test frequency.

[0012]

As is apparent from the above description, according to the present invention, the high voltage output of the high voltage output transformer is applied to the device under test through the inductor, so that even if a minute corona occurs, the expansion is achieved. The corona voltage having a sufficient amplitude can be detected, and the detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing one embodiment of a withstand voltage test apparatus according to the present invention.

FIG. 2 is a diagram showing a model circuit for explaining generation of corona.

FIG. 3 is a diagram showing a model circuit for explaining detection of a corona voltage.

FIG. 4 is a diagram showing another embodiment of the withstand voltage test apparatus according to the present invention.

FIG. 5 is a diagram showing a circuit configuration of a conventional interlayer withstand voltage test device.

[Explanation of symbols]

1 ... Test power supply, 2 ... High voltage output transformer, 3 ... Inductor, 4 ... DUT, 5 ... High pass filter, 6 ... Corona voltmeter

Claims (2)

[Claims] 1. A withstand voltage test apparatus for detecting a corona voltage generated in a device under test by applying a voltage from the test power supply to the device under test, and connecting an inductor in series between the test power supply and the device under test. A withstand voltage test device characterized in that 2. A withstand voltage test apparatus according to claim 1, wherein a capacitor is connected in series with the inductor and a resonance frequency of a series resonance circuit of the inductor and the capacitor is set to a test frequency.