JPH07128392A - Nondestructive insulation tester - Google Patents

Abstract

PURPOSE:To make it possible to nondestructively detect defective insulation of a motor caused by contact of conductors, i.e. layer short, by detecting insulation of an enamel wire, i.e. a flaw thereon, being employed in the stator or rotor of a motor. CONSTITUTION:A specimen 1, i.e., a stator or a rotor employing an enamel wire, is placed in a pressure reducing vessel 2. Pressure in the vessel 2 is then reduced and a constant AC voltage is applied to the specimen 1. A vacuum corona measuring unit 9 detects corona discharge at a detection sensitivity equal to a predetermined amount of discharged charges. A pulse counting circuit 10 counts the generation frequency and decides pass/fail of the specimen 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-destructive insulation tester for detecting an abnormal enameled wire insulation occurring in a manufacturing process of a motor, a transformer or the like in a reduced pressure state.

[0002]

2. Description of the Related Art (1) In the manufacture of a motor used for home electric appliances and the like, the process of winding an enamel wire or the like around an iron core and mounting it on a stator or a rotor is automated by a robot or the like. During this process, the enamel wire may have abnormal insulation, which is a serious problem in quality control.

Two phenomena have been considered for such insulation failure. That is, one is the case where the disturbed enamel wire directly touches or comes very close to the iron core due to turbulence of the enamel wire, spillage, misalignment of the spacers, etc., and insulation failure is likely to occur at this portion. On the other hand, the other is scratches of the enamel wire itself, peeling of the enamel layer, and the like, and a conductor contact, that is, a rare short circuit occurs between the enamel wires due to changes over time, which causes insulation failure.

In order to detect these defects, inspection methods such as visual inspection and AC withstand voltage test are carried out. In these tests, defects due to contact between the enamel wire and the iron core caused by disturbance of the enamel wire, etc. Cannot be detected accurately.

In order to solve this problem, for example, in Japanese Patent Laid-Open No. 3-246472, a corona discharge is used.
An apparatus for detecting a state where an electric wire and an iron core approaching each other of about mm or less is disclosed. This is because a stator or rotor, which is a member of a motor in which an enamel wire or the like is wound around an iron core, an AC voltage of 800 V to 1200 V is applied between the enamel wire and the iron core, and the corona discharge charge amount generated at this time is measured by the corona discharge charge amount. This is a device that measures with a measuring instrument and judges that the discharge charge amount increases rapidly as a defective product and sorts it on the inspection line.The enamel wire and the iron core are It has a substantially satisfactory effect for detecting the state of contact or very close contact.

(2) On the other hand, a conductor contact, that is, a rare short circuit occurs between the electric wires due to a scratch on the enameled wire itself wound around the iron core of the stator or rotor, and the motor is completed and installed in an air conditioner or a refrigerator, for example. During use as a product, insulation deterioration may be gradually promoted, resulting in insulation breakdown and motor burnout. Therefore, this becomes a serious problem in terms of maintenance and affects the reliability of product quality.

Therefore, Japanese Patent Publication No. 5-49065 discloses a non-destructive inspection method utilizing the so-called Paschen's principle that the spark discharge voltage decreases as the atmospheric pressure decreases. This introduces volatile gas into the vacuum container,
This is a method to detect the arc discharge generated by applying a voltage between the enamel wire used in the stator and rotor and the mesh electrode, and the arc discharge generated from the scratched part of the enamel wire by a relatively low applied voltage in vacuum. , Which is colored with a volatile gas and visually detects scratches.

[0008]

[Problems to be Solved by the Invention] (a) However,
The first conventional example of (1) is effective for detecting when the enamel wire is very close to the iron core due to spillage or the like, but conductor contact between the enamel wires due to damage to the enamel wire, that is, a rare short circuit It is not possible to detect a flaw when there is a crack or when the flaw of the enamel wire and the iron core are separated by several mm or more. For this reason, an impulse test or a rare short test has been performed, but in this case, only some defects can be detected, and the test takes time, which is not a practically effective method.

(B) Further, in the above-mentioned second conventional example, since the arc discharge is visually detected, it is disadvantageous in detecting relatively small scratches, and scratches in hidden portions that do not appear on the surface. Difficult to detect. Further, the visual determination requires manpower and individual differences occur, and since the degree of vacuum is as high as 0.5 Torr, it takes time to reach the degree of vacuum, and a large capacity vacuum pump is required. In addition, containers and the like are required to have high airtightness to prevent vacuum leaks, which makes it expensive to manufacture equipment such as machining. Therefore, it is extremely difficult to incorporate this method into an automatic inspection line for 100% check.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a non-destructive insulation test apparatus capable of automatic inspection by solving the problem of defective conductor contact between enameled wires, that is, a short circuit.

[0011]

A nondestructive insulation test apparatus according to the present invention for achieving the above object uses a member using an enameled wire as a subject, and seals the periphery of the subject to reduce the pressure. And a corona detecting means for detecting a corona discharge having a discharge charge amount of a predetermined amount or more generated by applying a constant voltage to the enamel wire in a depressurized state by the pressure reducing means, and the corona detecting means. Pulse counting means for counting the frequency of occurrence of corona discharge, and determination means for determining whether the insulation state of the subject is good or bad, based on the frequency of corona generation obtained by the pulse counting means. To do.

[0012]

The non-destructive insulation test device having the above-mentioned structure seals the subject, which is a member using the enamel wire, in the container,
A constant voltage is applied to the enamel wire in a state where the container is depressurized by the depressurizing means, and the frequency of corona discharge of a predetermined discharge charge amount or more generated at this time is counted to non-destructively check the insulation quality of the subject. Make a distinction.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiments. FIG. 1 is a block diagram showing the configuration of this embodiment,
1 shows a test device for detecting scratches on an enameled wire used in a small motor. The subject 1 in which an enameled wire or the like forming a motor stator or rotor is wound around an iron core is
The decompression container 2 is designed to be hermetically sealed.
A vacuum pump 4, a vacuum gauge 5, and an intake pipe 6 for releasing the vacuum are provided through the pressure reducing valve 3.

A general electric tester 8 including an air corona measuring instrument can be connected to the enamel wire of the subject 1 through a test end 7 and a blocking coil L, which is in parallel with the blocking coil L. The vacuum corona measuring instrument 9 is connected via the coupling capacitor Ck. Vacuum corona measuring instrument 9
A pulse counting circuit 10 and a pass / fail judgment circuit 11 are sequentially connected to. The entire apparatus is automatically controlled by a control mechanism such as a sequencer (not shown).

The general electric tester 8 includes, in addition to the air corona measuring device, a resistance measuring device, an insulation testing device, a rotation testing device, an AC withstanding voltage testing device, a waveform measuring device and the like.

At the time of measurement, the subject 1 is moved along the inspection line and attached to a predetermined inspection position in the decompression container 2 automatically or manually. Here, the test end 7 is connected to the enamel wire of the subject 1. When the measurement start switch is input, the cover of the decompression container 2 is closed to seal the subject 1, and at the same time, the vacuum pump 4 is driven. Decompression container 2 in a few seconds
When the inside pressure is reduced to a predetermined pressure, for example, about 20 Torr, the voltage application circuit of the vacuum corona measuring device 9 applies 500 to the subject 1.
An alternating constant voltage of V to 800 V is applied.

At this time, the corona discharge generated from the scratched portion of the enameled wire is detected by the vacuum corona measuring device 9, and the predetermined discharge charge amount, for example, the detection sensitivity of one corona discharge is 100.
The pulse counting circuit 10 counts the frequency of occurrence of corona discharge indicating a discharge charge amount of 0 × 10 ³ pC or more, and a predetermined value of this frequency of occurrence, for example, 20 ppS, is measured by the subject 1
The quality determination circuit 11 performs determination as a quality determination criterion.

When the measurement of the vacuum corona measuring device 9 is completed,
The airtightness inside the decompression container 2 is released, and the tests by the above-described general electric tester are sequentially performed. Based on the information on these test results, the final pass / fail determination is pass / fail determination circuit 11
The test object 1 is transported to the next step.

When the subject 1 is, for example, a stator or rotor of a small motor, scratches on the enameled wire often occur mainly when the enameled wire is attached to the iron core, and as shown in FIG. With the upper end as the center O, a large amount occurs between the ± 10 mm portion of the enamel wire 13, that is, the portion A at the upper side of about 10 mm and the portion B hidden at the inside of the iron core 14 at the lower side of about 10 mm.

Further, under reduced pressure, 10 Torr, 20 Torr, 30
When vacuum corona measurement was performed using a good quality enameled wire at Torr and 40 Torr, the results shown in Table 1 were obtained.

[0021] Table 1 corona discharge occurrence frequency down pressure of the sample NO. 40Torr 30Torr 20Torr 10Torr 12345 12345 12345 12345 ppS ppS ppS ppS 1 00000 00000 00000 00000 2 00000 00000 00000 01000 3 00000 00000 00000 00000 4 00000 00000 00100 00000 5 00000 00000 0000 00000 6 0000 0000 0000 0000 010 7 0000 0000 0000 00000 00000 8 0000 00000 00000 00000 00000 9 0000 0000 0000 0000 0000

Here, sample Nos. 1 to 9 show sample numbers of non-defective enamel wires, and the applied voltage at this time is 800V,
The detection sensitivity is set to 1000 × 10 ³ pC. Furthermore, the numbers 1 to 5 under each pressure reduction degree indicate that corona measurement was performed 5 times at that pressure reduction degree, "0" indicates that no corona discharge occurred, and "1" indicates 1 ppS
Indicates that a corona discharge has occurred. From these results, it can be seen that no corona discharge with a frequency of 2 ppS or higher is generated under any pressure reduction.

Therefore, in the case of a non-defective enameled wire, the detection sensitivity is 1 at an applied voltage of 800 V or less even under reduced pressure.
Almost no corona discharge of 000 × 10 ³ pC or more is generated.

Next, in the case of an enameled wire having a flaw, the distance between the flaw 15 of the enameled wire 13 of FIG. 3 and the iron core 14 is defined as a gap G. When the gap G is several mm or more, the atmosphere Inside, the detection sensitivity is 1000 × 10 ^3.
Since the corona discharge of pC is not detected as in the case of the non-defective product, it is not possible to discriminate the scratch in the atmosphere. That is,
The air corona measurement is effective for detection when the enamel wire 13 is almost in contact with the iron core 14, but it is difficult to detect scratches when the gap G is several mm or more.

Then, when the frequency of corona discharge occurrence was measured by decompressing the surroundings and measuring the vacuum corona, the results shown in Table 2 were obtained.

Table 2 Corona Discharge Occurrence Frequency Reduction Pressure Sample N0. Applied Voltage 10Torr 20Torr 30Torr 40Torr 300V 0ppS 0ppS 0ppS 0ppS 400V 16 0 0 0 500V 70 70 21 0 0 0 10 600V 157 V 9 70 6 70 0 14 0 900V 1184 1114 52 10 300V 0 0 0 0 400V 11 0 0 0 500V 52 20 20 0 0 11 600V 98 47 47 0 0 700V 980 1000 5 0 0 800V 1200 300 1218 18 0 900 900 0 2300 2411 0 0 0 500V 50 25 25 0 0 12 600V 220 153 300 0 0 700V 1280 1383 0 0 800V 1500 1500 13 15 0 900V − − Dielectric breakdown 32

Here, sample Nos. 10 to 12 show sample numbers of enameled wires having scratches, and the gap G is 10 mm,
Detection sensitivity is 1000 × 10 ³ pC, and decompression degree is 10 Torr
1000 × 10 ³ pC generated at this time by applying a constant voltage from 300 V to 900 V in sequence at ˜40 Torr
The above frequency of corona discharge was integrated by the pulse counting circuit 10.

The occurrence frequency other than "0" indicates that corona discharge is occurring. However, considering some errors in measuring instruments and measuring operations, 20 ppS is determined as the boundary value for pass / fail judgment. It is concluded that is empirically and practically valid.

Further, from Table 2 above, the pressure reduction degree is 30 Torr,
At 40 Torr, no significant difference is observed unless the applied voltage is 700 V to 900 V, and there are some that cause breakdown at 900 V like the enamel wire of No. 12, and this decompression degree is not appropriate from the viewpoint of nondestructive inspection. . On the other hand, 1
Under a reduced pressure of 0 Torr and 20 Torr, a significant difference is observed at 400 V and 500 V, so it can be seen that a reduced pressure of 20 Torr or less is appropriate for the discrimination.

Further, considering that the vacuum corona measuring instrument 9 is used by incorporating it in the inspection line, if a too low pressure reduction degree is required, the airtightness of the pressure reducing container, the capacity of the vacuum pump, the time required for reaching the pressure reduction degree, etc. Problems arise, which results in extra costs and practical disadvantages. Therefore, the test under the reduced pressure of about 20 Torr has the highest inspection efficiency.

As described above, a relatively high voltage is required to generate corona discharge in a good-quality enamel wire that is not damaged in the air, and even a enamel wire that has minute damage or a good product that is not damaged. Even with the enamel wire, the corona generation start voltage does not change much. On the other hand, under reduced pressure, the detection sensitivity is 1000 V or more for good products with a detection sensitivity of 1000
While a corona discharge of × 10 ³ pC occurs, as shown in Table 2 in the case of a scratched enameled wire, it is from 400 V at 10 Torr to 500 at 20 Torr.
Corona discharge with a detection sensitivity of 1000 × 10 ³ pC is generated from V. Therefore, it can be concluded that scratches can be reliably detected by setting the applied voltage of 500 V to 800 V as the test voltage for corona measurement. Further, in order to accurately determine a defect due to a scratch on the enamel wire, it is more efficient to use a voltage as high as possible within the range of 750 V to 800 V as a test voltage.

From the above results, at a reduced pressure of 20 Torr, a voltage of 800 V was applied, and the corona discharge charge amount of 1000 × 10 ³ pC detected at this time was set as the detection sensitivity. Frequency of occurrence is 20
By discriminating ppS or more as a defective product, it becomes possible to detect a flaw defect of the enamel wire and inspect the motor and the like nondestructively.

[0033]

As described above, the non-destructive insulation test apparatus according to the present invention applies a constant voltage to a member using an enameled wire in a depressurized container to measure a predetermined discharge charge amount by a corona discharge measuring instrument. By counting the frequency of occurrence of corona discharge above, non-destructive detection of scratches on the enameled wire can be performed to prevent the occurrence of defective products due to conductor contact, that is, a rare short circuit, which occurs due to changes over time after the product is completed. it can.

[Brief description of drawings]

FIG. 1 is a block circuit configuration diagram of an embodiment.

FIG. 2 is a perspective view of a joint portion between an electric wire and an iron core.

FIG. 3 is an explanatory diagram of a gap between a scratched portion and an iron core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test object 2 Decompression container 4 Vacuum pump 5 Vacuum gauge 8 General electrical tester 9 Vacuum corona measuring instrument 10 Pulse counting circuit 11 Pass / fail judgment circuit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Takashi Kikuchi, Inventor Takashi Kikuchi 3-4-1, Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Cable Co., Ltd. Tokyo Office (72) Inventor Shunichi Sakae Otani, Okamoto-cho, Kusatsu, Shiga Prefecture No. 2 at 1000 Daikin Industries, Ltd. Shiga Works (72) Inventor Ryoma Kurokawa Otani, Okamoto-cho, Kusatsu City, Shiga Prefecture No. 2 at Daikin Industries Co., Ltd. Shiga Works

Claims (2)

[Claims] 1. A subject using an enameled wire as a subject,
Decompression means for decompressing by sealing the periphery of the subject,
Corona detecting means for detecting a corona discharge having a discharge charge amount of a predetermined amount or more generated by applying a constant voltage to the enamel wire in a depressurized state by the depressurizing means, and a frequency of occurrence of corona discharge obtained from the corona detecting means. A non-destructive insulation test apparatus comprising: a pulse counting unit that counts the number of pulses, and a determination unit that determines whether the insulation state of the subject is good or bad based on the frequency of corona generation obtained by the pulse counting unit. . 2. The decompression range of the decompression means is about 20 To.
rr or less, the applied voltage range is set to 500 V to 800 V by the corona detecting means, and about 1000 × 10 ³ pC
A discharge with a corona discharge charge amount of (pico coulomb) or more is detected, and the occurrence frequency of corona discharge is determined by the pulse counting means to be about 20 ppS (the number of pulses per second) or more and the determination means to determine the subject as a defective product. The nondestructive insulation test apparatus according to claim 1.