JP3141813B2 - Dielectric strength test method using resonance type dielectric strength test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing the withstand voltage of a capacitive work such as a transformer, a common coil or a capacitor.

[0002]

2. Description of the Related Art FIG. 8 is a schematic circuit diagram of a conventionally known resonance type dielectric strength voltage testing apparatus, and FIG. 9 is an equivalent circuit thereof.

The resonance type dielectric strength voltage test apparatus generates a high voltage AC power supply for a dielectric strength voltage test using a resonance phenomenon of a resonance circuit. An oscillator 1 for oscillating a clock signal is used as an AC signal source, and a power amplifier 2 and a step-up transformer
The oscillating voltage obtained by current / voltage amplification through the above-described process is converted into a resistance R, an inductance L of an adjusting coil, and a capacitance C of a capacitive work 4 (actually, a capacitance C ′ of a jig 5 for setting the work 4). And resonates at a predetermined resonance frequency set in advance, and a high-voltage AC power supply generated at this time is used as a prescribed test voltage as the test voltage. It is configured to be applied to both ends of the work 4 set on the tool 5.

The resistance R of the LCR series resonance circuit is
This is for suppressing the sharpness of the resonance and reducing the fluctuation of the test voltage due to the variation of the work capacity.

In the equivalent circuit of the resonance type dielectric strength device shown in FIG. 9, the combined capacitance of the work 4 including the jig 5 is C, the test angular frequency of the oscillator 1 is ω, and the resonance angular frequency of the test device is Is ω0,

By setting the inductance L of the adjusting coil so that ω0 = (LC) ^{−1 / 2} = ω, the LCR series resonance circuit can resonate at the test angular frequency ω, At this time, the voltage applied to both ends of the work 4, that is, the test voltage Vc becomes the maximum.

Accordingly, the inductance L is adjusted in accordance with the capacity of the work 4 to set the resonance frequency of the test apparatus, and the test voltage Vc obtained at the time of resonance is adjusted to the specified voltage value specified by the dielectric strength test standard. By adjusting the oscillating voltage e0 of the oscillator 1 as described above, a predetermined withstand voltage test can be performed at a low oscillating voltage e0.

[0007]

However, as described above, the resonance angular frequency ω0 of the test apparatus determined by the capacitance C of the work 4 and the inductance L of the adjusting coil is set to the same value as the test angular frequency ω. In this case, even in the withstand voltage test of the work 4 having the same standard capacity, the test voltage Vc generated by the fluctuation of the resonance point for each work 4 greatly changes due to the substantial variation of the work capacity C. Resulting in.

For this reason, it is necessary to adjust the oscillation voltage e0 of the oscillator 1 each time in order to always set the test voltage Vc to a specified value during the withstand voltage test. Had become something.

Further, under such resonance conditions, the generated test voltage Vc changes in a direction lower than the specified value regardless of whether the work capacity C is larger or smaller than the standard capacity. It was difficult to estimate the variation of the work capacity C from the change amount of Vc and determine the defective work.

An object of the present invention is to provide a dielectric strength voltage test method using a resonance type dielectric strength voltage test apparatus capable of realizing a quick and highly reliable dielectric strength voltage test.

[0011]

That is, according to the present invention, an LCR series comprising a resistance (R), an inductance (L) and a capacity (C) of a work (4) set therein. In the method for testing the dielectric strength voltage of a work (4) using a resonance type dielectric strength voltage test apparatus for generating an AC test voltage (Vt) having a predetermined frequency using a resonance circuit,
The resonance frequency of the CR series resonance circuit is set to the test voltage (Vt).
And higher than the maximum work capacity (C) that is set in consideration of the work capacity variation, and at the time of the insulation withstand voltage test, first, the LC
The voltage applied to the work (4) during resonance of the R series resonance circuit
The initial oscillation voltage at which the voltage reaches the maximum voltage that does not exceed the specified value
Voltage (e0) and oscillate the initial oscillation voltage (e0)
Based on the initial applied voltage (V0) generated by the vibration voltage (e0).
The test oscillation voltage (et) is calculated based on the
Oscillates the specified test oscillation voltage (et)
Pressure (Vt) is generated .

[0012]

[0013] In the present invention according to claim 2, characterized in that the workpiece (4) is a transformer with a primary winding and a secondary winding.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In a resonance-type insulation withstand voltage test device (hereinafter referred to as a withstand voltage test device) having an equivalent circuit shown in FIG. 9, if the angular frequency of an AC power supply is ω, the impedance Z of the resonance circuit becomes

## EQU2 ## When Z = R + j (ωL-1 / ωC), and the oscillation voltage from the oscillator 1 is e0, the test voltage Vc applied to both ends of the work 4 is expressed by the following equation (2).

Vc = e0 / ((1−ω ² LC) + jωCR) where the test voltage Vc is the resonance angular frequency ω
It becomes maximum at 0.

By the way, as described above, in the case of the conventional withstand voltage test apparatus, the resonance angular frequency ω0 is set to substantially the same value as the test angular frequency ω, whereas the first embodiment of the present invention. In this example, the inductance L is set so that the resonance angular frequency ω0 is higher than the test angular frequency ω.

Now, in FIG. 8, the standard capacitance is 100 pF.
The work 4 is 1500 at a test frequency of 70 KHz.
It is assumed that a withstand voltage test of V is performed.

In the conventional method, the inductance L (L is calculated by the equation (1) so as to resonate at the test frequency of 70 KHz.
= 51.7 mH), but in the case of the first embodiment, it resonates at a higher frequency, and its resonance point is the maximum determined in consideration of the variation in the work capacity. Inductance L so that it becomes more than work capacity C
(L = 46.3 mH) is set. In this case ,
Resonance frequency is set to 74 kHz.

The characteristic shown in FIG. 6 is obtained by calculating the change in the test voltage Vc with the change in the work capacity based on the set inductance L according to the equation (3), and plotting the test voltage value with respect to the work capacity. Things. In the figure, characteristic A
Represents a conventional method in which the resonance frequency of the test apparatus is set to 70 KHz, and characteristic B represents the first embodiment in which the resonance frequency is set to 74 KHz.

In the first embodiment, e0 in the equation (3) represents the secondary voltage of the step-up transformer 3, and the test voltage is 1500 at the point of 100 pF which is the standard capacitance value of the work 4.
The oscillation voltage of the oscillator 1 is adjusted to be V.
That is, the resonance point of the characteristic B is set to the work capacity of 110 pF, and the resonance voltage generated at this time is about 2400V.

Therefore, as is apparent from FIG. 6, in the conventional method in which the resonance frequency of the test apparatus is set to 70 KHz, which is the same as the test frequency, the test voltage Vc is the maximum when the work capacitance C is 100 pF, which is the standard capacitance. (1500V)
Thus, the test voltage Vc decreases regardless of whether the work capacity C becomes larger or smaller.

On the other hand, in the first embodiment, as described above, the test frequency is 70 KHz, and the work capacity has a resonance point at 110 pF. Therefore, when the work 4 having a capacity smaller than the standard value (100 pF) is set. When a test voltage Vc lower than 1500 V is applied and a work 4 having a capacity larger than the standard value is set, a higher test voltage Vc is set.
c is applied.

As described above, according to the first embodiment of the present invention, when the oscillation voltage e0 is constant, the withstand voltage test is performed based on the change in the test voltage Vc applied to the work 4 at that time. It is possible to estimate whether or not the capacity of the work 4 is within an allowable variation range (for example, if the work 4 has a standard capacity of 100 pF, the variation range is 90 to 110 pF).

Therefore, by setting the characteristic of the test voltage Vc in the withstand voltage test apparatus as shown in FIG. 6B, for example, when testing the insulation withstand voltage of the transformer, the transformer primary winding is determined from the test voltage generated at that time. By estimating the variation in the spatial distance between the secondary winding and the secondary winding, defective products can be selected.

FIG. 1 is a schematic block diagram of a withstand voltage test apparatus according to a second embodiment of the present invention. In the conventional withstand voltage test apparatus, a test voltage monitoring unit 8, an oscillation voltage control unit 6, and This is an automatic insulation withstand voltage test apparatus that can automatically and instantaneously set the applied voltage (test voltage Vc) to the work 4 when the withstand voltage test is performed by including the controller 9 for controlling these.

FIG. 2 shows the specific configuration. The oscillator 1 whose output is variable by the controller 9 is used as the oscillation voltage control unit 6, the combination of the resistor R and the inductor L is used as the resonance adjustment unit 7, and the test voltage monitor is used. A voltmeter is used as the unit 8.

Next, a withstand voltage test method according to the second embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing an automated withstand voltage test method, and FIG. 7 shows a test voltage vs. work capacity characteristic set for carrying out this test method.

First, before starting a withstand voltage test, test conditions, that is, a test voltage Vt value (for example, 1500 V),
The test frequency f value (for example, 70 KHz) is input to the controller 9.

By the way, in a resonance type withstand voltage test apparatus,
If the secondary voltage of the step-up transformer 3 is constant, the maximum test voltage when the work capacity C varies is the voltage at the time of resonance. The minimum necessary secondary voltage of the step-up transformer 3 for obtaining is also the voltage at the time of resonance.

Therefore, as a first step of the withstand voltage test, a prescribed test voltage (1500 V) is set based on the previously inputted test conditions within a range of variation in the capacity of the workpiece 4 to be subjected to the withstand voltage test. The maximum oscillating voltage of the oscillator 1 which does not exceed, that is, the initial oscillating voltage e0 for obtaining a specified test voltage at the time of resonance is calculated, and under the control of the controller 9, the initial oscillating voltage calculated by controlling the oscillating voltage control unit 6 is calculated. oscillating the oscillation voltage e0 (According to Figure 7, the step-up transformer 3
The secondary voltage is set at about 110V).

Here, the initial oscillation voltage e0 can be calculated by the following procedure, for example.

The voltage Vc applied to the work 4 at the time of resonance is given assuming that the secondary voltage of the step-up transformer 3 is E2.

Equation 4] Vc = - can be represented as jω0 L · E2 / R.

Further, since the amplification degree of the power amplifier 2 and the boost ratio of the boost transformer 3 are known, the relationship between the oscillation voltage at the time of resonance and the test voltage can be easily obtained from the equation (4). Therefore, from the above relationship, the initial oscillation voltage e0 can be calculated from the function g (f, Vt) of the test frequency f and the test voltage Vt. As another method, the above calculation result may be set in the form of a table in advance and referred to each time.

Next, as a second step of the withstand voltage test,
When the initial oscillation voltage e0 is oscillated, an initial applied voltage V0 applied to both ends of the work 4 is measured by the test voltage monitoring unit 10, and the preset initial oscillation voltage e0 and test voltage Vt are determined by: An oscillation voltage et for obtaining a prescribed test voltage Vt (1500 V) is calculated from a function h (e0, V0, Vt) using the measured initial applied voltage V0 as a parameter.

For example, the oscillation voltage et can be obtained by a proportional calculation according to the equation (5).

[0035]

[Equation 5] et = Vt · e0 / V0 Next, the oscillation voltage calculated by controlling the oscillation voltage control unit 6
A test voltage is applied by et and the specified withstand voltage test is performed.

[0036] For example, FIG. 7 is resonance point work capacity 110
With a withstand voltage tester set to pF, a standard capacity of 10
This shows test voltage characteristics when a withstand voltage test is performed on a work 4 having a test voltage of 1500 V at 0 pF. In the figure, the characteristic A is set in the first step described above, and the test voltage characteristic at the initial oscillation voltage at which the test voltage becomes 1500 V at the time of resonance, while the characteristic B is set in the second step described above. Test voltage is 1500V with work capacity of 100pF
The test voltage characteristic at the oscillation voltage such that the characteristic C is the secondary voltage of the step-up transformer 3 corresponding to each work capacity for setting the test voltage to 1500 V.

In the first embodiment, the resonance frequency of the test apparatus is set to be higher than the test frequency (for example, 74 KHz), and the voltage at the time of resonance at which the applied voltage becomes maximum is used as the test voltage. Unlike the conventional method, the oscillation voltage is set so that the specified test voltage 1500 V can be obtained at the point of the standard capacitance 100 pF outside the resonance point. May be applied, and this may lead to destruction of the work 4. Therefore, in the withstand voltage test, it is necessary to gradually increase the oscillation voltage so that the voltage applied to the work 4 does not exceed the prescribed test voltage of 1500 V. However, this takes too much time to set the voltage. The withstand voltage test becomes complicated, and an error occurs in the application time of the test voltage.

However, according to the above-described second embodiment, the specified test voltage is automatically calculated and set based on the preset test conditions.
There is no need to worry that a voltage higher than the specified voltage is applied. Therefore, the prescribed test voltage can be set safely in a short time.

Further, in the second embodiment, as shown in the flowchart of FIG. 4, by setting the allowable minimum voltage VL1 which is determined in advance in consideration of the variation of the work capacity, the above-described withstand voltage test is performed. In the first step, when the initial test voltage V0 generated by the initial oscillation voltage e0 becomes equal to or lower than the allowable minimum voltage VL1, it is determined that the work 4 is not correctly set on the jig 5 and the withstand voltage test is stopped. Can be controlled to This is because, since the applied voltage depends on the capacitance C, the work capacitance C becomes smaller than the variation range due to a defective setting of the work 4, and
This is because it can be determined that the applied voltage has dropped extremely.

Now, assuming that a setting failure of the work 4 occurs, as shown by a characteristic A in FIG.
Is the only capacity C ′ of the jig 5, so the minimum work capacity (for example, 90 pF) in consideration of the variation
And the initial applied voltage V0 is reduced to the minimum capacitance of 90 pF.
, That is, lower than the permissible minimum voltage VL1 (about 550 V in FIG. 7), it is determined that the work 4 is set improperly.

The automatic withstand voltage test according to the second embodiment is a control mode in which a specified test voltage is applied by automatically changing an oscillation voltage according to a change in work capacity. Even if the work 4 is not properly set as described above, the withstand voltage test may be performed. However, by setting the allowable minimum voltage VL1 as described above and checking this, Since the setting failure of the work 4 can be detected before the withstand voltage test at the specified voltage is performed, such inconvenience is prevented, and the highly reliable withstand voltage test can be performed on all the works 4.

Further, in the second embodiment, as shown in the flowchart of FIG. 5, by setting the allowable minimum voltage VL2 in advance, the voltage withstand voltage test is performed in the second step of the withstand voltage test. Test oscillation voltage et during
When the test voltage Vt generated by the above becomes less than the allowable minimum voltage VL2, it is judged that the work 4 has caused dielectric breakdown and the work capacity C has increased beyond the range of variation, and the withstand voltage test is stopped. Can be controlled as follows.

For example, under the test conditions (characteristic B) shown in FIG. 7, the allowable minimum voltage VL2 is set to about 850V. This voltage value is equivalent to 130 pF when converted to the work capacity, and greatly exceeds the variation range of the capacity of the work having the standard capacity of 100 pF (maximum 110 pF).

The setting failure of the work 4 and the occurrence of the dielectric breakdown are all judged by the controller 9 based on the measurement data by the test voltage monitoring unit 8. When an abnormality is detected, the oscillation voltage Since the control unit 6 is controlled and the oscillation voltage is automatically stopped,
Stopping the withstand voltage test when an abnormality occurs is performed very accurately.

[0045]

As described above, according to the first aspect of the present invention, in the insulation withstand voltage test using the resonance type insulation withstand voltage test apparatus, the resonance frequency of the test apparatus is set higher than the test frequency. If the oscillation voltage is constant, the test voltage changes in one direction in accordance with the work capacity if the oscillation voltage is constant. Therefore, it is possible to estimate the variation in the work capacity based on the test voltage. Therefore, when the applied test voltage is monitored during the insulation withstand voltage test, it is possible to detect a work defect. Especially withstand voltage test
First, in the first step, set the test conditions set in advance.
Set the initial oscillation voltage, and then in the second step
From the initial applied voltage generated by the initial oscillation voltage,
Calculate the test oscillation voltage and oscillate this test oscillation voltage.
To obtain the specified test voltage.
Test voltage higher than the specified
And the work breakdown due to overvoltage is prevented.
In both cases, the specified test voltage can be set in a short time with this method.
Because of this, a reliable and reliable withstand voltage test can be performed quickly and
Can be easily implemented.

[0046]

According to the second aspect of the present invention,
If the transformer is tested according to the insulation withstand voltage test method,
From the variation in the test voltage, it is possible to estimate the variation in the spatial distance between the primary winding and the secondary winding of the transformer.
Defective products can also be determined.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an insulation withstand voltage test apparatus according to the present invention.

FIG. 2 is a schematic circuit configuration diagram of the same device.

FIG. 3 is a flowchart showing a procedure of an insulation withstand voltage test according to the present invention.

FIG. 4 is a flowchart showing a procedure for determining a work setting failure in an insulation withstand voltage test.

FIG. 5 is a flowchart showing a procedure for judging the destruction of a work in the automatic withstand voltage test.

FIG. 6 is a diagram showing a change in test voltage according to a change in work capacity.

FIG. 7 is a diagram showing a change in test voltage according to a change in work capacity, which is different from that in FIG. 6;

FIG. 8 is a schematic circuit configuration diagram of a conventional resonance-type insulation withstand voltage test apparatus.

9 is an equivalent circuit diagram of FIG.

[Explanation of symbols]

 4 Work e0 Initial oscillation voltage V0 Initial application voltage et Test oscillation voltage Vt Test voltage

Continuation of front page (56) References JP-A-61-209361 (JP, A) JP-A-8-136609 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 27 / 00-27/32 G01R 31/12-31/20

Claims (2)

(57) [Claims] An L comprising a resistance (R), an inductance (L) and a capacity (C) of a set work (4).
In a method for testing a dielectric strength voltage of a work (4) using a resonance type dielectric strength voltage test apparatus for generating an AC test voltage (Vt) of a predetermined frequency using a CR series resonance circuit, the resonance frequency of the LCR series resonance circuit is It is set to resonate at a frequency higher than the test voltage (Vt) and at the maximum work capacity (C) which is set in consideration of the variation of the work capacity. At the time of resonance of the LCR series resonance circuit, an initial oscillation voltage (e0) is oscillated such that a voltage applied to the work (4) becomes a maximum voltage that does not exceed a specified value, and the initial oscillation voltage (e0) and the initial oscillation voltage A test oscillation voltage (et) is calculated based on the initial applied voltage (V0) generated by (e0), and then the calculated test oscillation voltage (et) is oscillated to determine a specified test voltage (Vt). Generate A dielectric strength test method using a resonance type dielectric strength test apparatus. 2. The method according to claim 1, wherein the workpiece is a transformer having a primary winding and a secondary winding.
3. A dielectric strength voltage test method using the resonance type dielectric strength voltage test apparatus according to 4.