JPH0549065B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for non-destructively electrically inspecting insulation defects (flaws) in low-pressure rotating machines such as air conditioner motors.

More specifically, insulation defects (scratches) in low-voltage rotating machines.
In order to detect the Surround it with detection electrodes, connect both to opposite poles of the power supply, apply electricity, reduce the pressure inside the container to create a vacuum, introduce volatile gas into the vacuum container, lower the discharge voltage, and generate a spark. In addition to making it easier to generate electric discharge, this method also colors the generated arc with volatile gas, making it extremely easy to visually identify insulation defects, and performing non-destructive testing.

(Prior Art) Low-pressure rotating machines that require high reliability, such as air conditioner motors, have a failure rate of 0.05% or less, but as users of rotating machines, we are working hard to further reduce the defective rate. However, in order to achieve this, the current quality control through sampling inspection is insufficient, and 100% inspection is absolutely necessary, and a non-destructive testing method as a means of 100% inspection must be established. However, most of the currently used methods involve the destruction of the inspected object, and even non-destructive testing methods are not sufficient to detect even the smallest defects. .

Figure 3 shows one of the inspection methods based on the conventional technology.
This method is based on the standard pinball test method. For example, the stator 1 of the motor (stator coil 2 wound around it) is immersed in a salt solution 3' containing phenolphthalene. When a DC power supply 5' and a voltage are applied between the lead wire 4' of the coil (stator coil) 2' and the saline solution 3', the stator coil 2 will be damaged (insulation defect) in the saline solution 3'.
If present, current will flow through the scratched area and electrolysis will occur. As a result, sodium hydroxide is generated and reacts with the phenol, turning that part of the saline solution red, and this color change makes it easy to visually identify the location of the flaw.

FIG. 4 shows a second example of the conventional inspection method, in which the outer periphery of the stator stator coil 2 wound around the stator 1 is covered with a conductive film 6'. When the air inside the conductive film 6' is removed using P or the like, the film 6' is brought into close contact with the stator coil 2. The film 6' applies voltage between the lead wires, and if an ammeter 7' is connected in the circuit, if there is a flaw somewhere on the stator coil, current will flow through the flaw, so the ammeter 7 It is possible to confirm the presence of scratches from the deflection of the pointer.

According to the conventional inspection method described above, the method shown in Figure 3 has the disadvantage that the test takes a long time because it is a visual inspection using a chemical method using an aqueous solution. Therefore, post-treatment such as washing with water and drying is required.

Furthermore, since this method is basically a destructive test, it is essentially inconvenient as a product inspection method.

On the other hand, the inspection method shown in Figure 4 essentially expects contact between the scratch and the film electrode, and
Although this is a method of applying a low voltage, scratches on the coil surface vary from relatively large to minute scratches, and in the case of minute scratches, the adhesion of the conductive film electrode 6 to the scratches is insufficient. Therefore, there is a disadvantage that it is impossible to detect even minute scratches.

In addition, the method shown in Figure 4 originally involves direct contact between the scratch and the film electrode, and there is no idea of detecting the defect by causing an electric discharge. I can't.

(Problems to be Solved by the Invention) The present invention solves the drawbacks of the prior art using Patschen's principle, and uses the phenomenon that discharge occurs at a relatively low voltage in a reduced pressure gas to This test uses low voltage to inspect for flaws on the outside of the child coil non-destructively and in a short time, and the presence or absence of flaws and their location can be observed extremely easily with the naked eye using a colored arc. The present invention provides a method.

Figure 2 shows the Patsien principle; if the pressure in the vacuum chamber (X-axis) decreases, the discharge voltage between the voltage-applied sample and the opposing detection electrode will decrease up to a certain value. Since the voltage rises again, attention is paid to the phenomenon that if the voltage is continuously lowered, discharge will start at some point.

(Means for Solving the Problems) According to the present invention, detection electrodes are arranged in double rows or in a single row on the outer periphery of a sample to be inspected, for example, a stator coil, and the electrodes are electrically connected between each other. The stator coils are insulated and placed at a distance sufficient to generate an arc under reduced pressure, placed in a vacuum container, and the lead wire of the stator coil is connected to one of the electrodes (either direct current or alternating current), for example, the positive electrode. A detection electrode is connected in series to the negative electrode of the electrode via an ammeter.
The pressure inside the vacuum container is reduced to 0.-2 mm using a vacuum pump, a voltage is applied between the lead wire and these electrodes, and when one of the switches is turned on, the lead wire is in contact with the detection electrode connected to that switch. If there is a flaw that causes insulation failure in the stator coil, the current due to discharge between the flaw and the electrode will be detected by an ammeter, indicating that the flaw exists in the coil area surrounding the detection electrode. can be detected.

In this case, if the applied voltage is changed continuously and a volatile substance such as dry ice, naphthalene, or mercury is placed in the vacuum container, the arc will be colored during discharge, which is extremely effective for visual judgment. When a volatile gas is introduced into a vacuum vessel under reduced pressure and a discharge is caused, the discharge arc is colored in a unique color depending on the volatile gas. This is a well-known phenomenon in tubes, where, for example, when carbon dioxide gas from dry ice is introduced, they take on a bluish green color.

The present invention utilizes the phenomenon that arcs are more likely to occur in a reduced pressure container as described above,
In order to nondestructively test electrical equipment such as motors for insulation defects, the equipment to be tested is housed in a depressurized vacuum container, and if there is an insulation defect, a discharge arc is generated, and the above-mentioned Combining the phenomenon that the discharge arc is colored in a unique color depending on the volatile gas introduced into it,
This problem has been solved by providing a non-destructive testing method that can clearly visually determine the presence or absence of arc occurrence and the location of arc occurrence.

(Embodiment) FIG. 1 shows an embodiment of the present invention, and parts that are the same as or equivalent to those in FIGS. 3 and 4 are given the same reference numerals and their explanations will be omitted. In FIG. 1, conductive mesh-shaped insulation defect detection electrodes 9 surround the outer periphery of each stator coil (stator coil) 2 at both axial ends of the stator.
are arranged in two rows with a predetermined spacing in the axial direction, and each is connected in series to the negative electrode of the electrode 4. On the other hand, the positive electrode is connected to the lead wire 3 of the stator coil 2 and the stator 1. In this state, the vacuum container 9 is depressurized using the vacuum pump 6.

If volatile substances such as dry ice, naphthalene, or mercury are placed in the vacuum container 9, they will vaporize as the pressure inside the container decreases and the arc will emit a unique color during discharge. Therefore, it is effective for visual judgment.

Turn on the switch connected to detection electrode 8
, a voltage is applied between the lead wire and this electrode. If there is a flaw in the part of the stator coil surrounded by these electrodes, a current will flow due to discharge under reduced pressure based on the Patsien principle, so the position of the flaw can be directly observed by the colored arc in the area where the arc occurs, and the current The presence of scratches can also be detected by Total 5.

The inspection method of the present invention utilizes Patschien's principle of spark discharge in air and the coloring of the arc by volatile substances. In other words, as shown in Figure 2, the voltage (V) at which sparks begin to fly between opposing electrodes placed at a distance d in the air is the pressure in the air (mmHg).
This method takes advantage of the phenomenon that the more the voltage decreases, the more the outage voltage becomes.

Therefore, in the present invention, since the pressure inside the container 9 is reduced to approximately 0.5 mmHg using a vacuum pump, spark discharge can be performed at a low voltage of 400 to 700V.

Therefore, even if a spark discharge occurs for inspection at a flaw in the stator coil, the voltage is only 400 to 700V.
Since the electric discharge is performed at a low voltage, there is no risk of the damage to the coil being enlarged, and after all, it is possible to carry out a non-destructive inspection that can identify the presence or absence of damage to the coil and its location.

In this example, a mesh electrode was used, but it is not limited to this. However, a mesh electrode is convenient for observing the location where the arc occurs, and even if the distance from the scratch is about 100 mm, the arc can be detected. We have confirmed that this occurs.

The reason why mercury, dry ice, naphthalene, etc. are used as volatile substances is because they are solid or liquid and do not require any particular piping and can be placed in a simple container.

(Effect of the invention) The present invention has the following advantages.

(1) Detection electrodes are placed around the outer circumference of the stator coil at appropriate intervals so that the inside can be observed, and each is connected to a power source through each electrode, and the detection electrodes are used together with a volatile substance in a depressurized vacuum container for inspection. By simply applying a voltage between the stator coil and the stator coil, it is possible to visually observe and identify the location of any flaws in the coil.

(2) In addition, since the detection electrode is used to perform the inspection under reduced pressure inside the vacuum container, it is possible to inspect even the smallest flaws with low voltage, and as a result, non-destructive inspection is possible in a short time. Since it is a low voltage of 700v or less, it is effective for 100% inspection of products without causing damage to the product due to discharge.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the invention, Fig. 2 is a graph for explaining the principle of patching used in the invention, and Figs. 3 and 4 are conventional methods for inspecting coil insulation defects. FIG. 2 is a schematic diagram for explaining the method. 1... Stator, 2... Stator coil, 3...
Lead wire, 4...Power source, 5...Ammeter, 6...Vacuum pump, 7...Volatile substance, 8...Mesh detection electrode, 9...Vacuum container.

Claims (1)

[Claims] 1. Conductivity detection electrodes are arranged to surround the outer periphery of a stator coil housed in a vacuum container and are spaced apart enough to be electrically insulated from each other, and one pole of a power source is is connected in series to the lead wire of the stator coil, and the other pole is connected in series to the conductivity detection electrode and energized to reduce the pressure in the vacuum container and introduce a volatile gas into the vacuum container, By coloring the arc generated between the flaws in the stator coil and the conductivity detection electrode, the existence and location of insulation defects in the stator coil can be determined non-destructively. A non-destructive inspection method for insulation defects in low-voltage rotating machines, characterized in that the defects can be easily detected visually. 2. In the method according to claim 1, the method for introducing a volatile gas into the vacuum container is to introduce a liquid or solid volatile substance such as mercury, dry ice, or naphthalene into the vacuum container in advance. A non-destructive inspection method for insulation defects in a low-pressure rotating machine, characterized in that each of the components is vaporized as a gas by placing the vacuum container and reducing the pressure in the vacuum container. 3. A low-pressure rotary machine according to claim 1 or 2, characterized in that the conductivity detection electrode disposed within the vacuum container is formed from a mesh-like conductive material. Non-destructive testing method for insulation defects.