JPS6235345B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention relates to insulated articles. [Prior Art] Conductors used as coils in generators and motors are manufactured using the VPI method (vacuum pressure impregnation) by wrapping the conductor with mica tape and then wrapping glass bonding tape over it to support the brittle mica tape. law)
Insulated using The conductor thus wrapped with insulating material is placed in a vacuum and then immersed in a resin under pressure, the conductor is removed and heated in an oven to harden the resin. [Problems to be Solved by the Invention] Although this method is used industrially, it requires a large amount of energy in the baking furnace because the copper in the coil must be heated together with the resin. The resin may flow out during the curing process, introducing mechanical stress into the resin by expanding the copper during curing and then contracting it during cooling. Anaerobic resins are resins that do not cure in the presence of oxygen, but do cure when placed between two oxygen-impermeable surfaces that are to be bonded together; therefore, they are commonly used as adhesives. be done. The purpose of the present invention is to insulate conductors such as copper used as coils of generators and motors.
The object of the present invention is to provide a method for insulating a conductor with resin at room temperature by solving the above-mentioned drawbacks associated with vacuum impregnation and heat curing by the VPI method. [Means for Solving the Problems] This invention provides (a) a conductor used as a coil in an electrical device that is reinforced with an insulating material or an impregnated reinforcing material, or a reinforcing material that is reinforced with an insulating material or an impregnated reinforcing material. (b) after placing the coated conductor in a vacuum; (c) embedding the coated conductor in an anaerobically curable insulating resin in an oxygen-containing atmosphere; (d) pressurizing the anaerobically curable insulating resin in the presence of oxygen; and (e) removing the conductor from the resin. (f) placing a conductor with a coating saturated with an anaerobically curable insulating resin into a resin curing zone in an oxygen-free gas atmosphere until said resin is cured; Vacuum-pressure insulation method for conductors used as [Function] The anaerobic resin in an insulated conductor impregnated with an anaerobic resin does not harden in a vacuum, which is advantageous in the VPI method, but it can harden by contacting with an oxygen-free gas atmosphere. was discovered. This means that the resin can be cured at room temperature, thus avoiding the problems hitherto encountered with thermoset resins. The electrical properties are equivalent to currently used thermosetting resins, except in the case of high voltage. Unlike electron beam cured resins and ultraviolet (UV) cured resins, anaerobic resins cured under gas cure to depths of 15.2 mm (6 inches) or more. For a clearer understanding of the invention, reference will now be made to the accompanying drawings, which illustrate and illustrate convenient embodiments thereof. In FIG. 1, a conductor 1 is covered with several layers of mica tape insulation 2 and a layer of organic woven tape insulation 3 which holds the mica tape insulation in place. Anaerobic resin 4 impregnates the insulation and forms the outer coating. In FIG. 2, conductor 5 passes from capstan 6 to bath 7 of anaerobic resin 8. In FIG. The wire then passes over a sheave 9 and enters a closed tank 10. Inert gas enters tank 10 through conduit 11. While the wire passes over the sheave 12 in the tank, the resin on the wire hardens, leaves the tank, and is wound onto the capstan 13. Anaerobic resins are resins that do not cure in the presence of oxygen, but cure at room temperature when placed on two oxygen-impermeable surfaces that are to be bonded together.
A solvent-free anaerobic resin is required for the VPI method. Most anaerobic resins are acrylic resins such as diacrylates, which polymerize by double bond addition. Commonly used acrylic anaerobic resins include tetraethylene glycol dimethacrylate and tetraethylene glycol diacrylate. Acrylic anaerobic resins can contain reactive comonomers such as ethyl methacrylate, styrene or 2-ethylhexyl acrylate. Organic peroxide free radical initiators such as cumene hydroperoxide or t-butyl perbensoate are often used to initiate the curing reaction. N,N-dimethyl-p
- Accelerators, usually tertiary amines such as toluidine, and co-promoters, usually organic sulfimides such as benzoic acid sulfimide, may also be present to reduce curing time. Free radical initiators can be stabilized with free radical stabilizers such as hydroquinone. The conductor is preferably copper. This is because copper is most commonly used in coating electrical insulation and it is also known to accelerate the curing of anaerobic resins. The primary insulating material is preferably mica, which has excellent electrical properties, especially at high voltages. Glass, asbestos, Nomex (trade name, manufactured by Dupont, believed to be a polyimide made from metaphenylene diamine and isophthalic acid chloride) and other types of electrical insulation may also be used alone or in combination. hand,
Or it can be mixed with mica. Mica insulation is constructed using a polyester backing to hold the mica in a continuous state. This insulation material is often tape, which is wrapped around the conductor. The amount of insulation varies depending on the voltage drop across the insulation. The mica insulation material contains a polymer co-reactive with the anaerobic resin in an amount of about 3 to 30% by weight based on the weight of the mica (preferably about 30% by weight based on the weight of the mica) to better bond with the anaerobic resin. It is preferred to use pre-impregnated mica insulation (5% to about 12% by weight). Polyesters, acrylics, polybutadiene, or other unsaturated monomers can be used as co-reactive resins. The VPI method is the preferred method of insulating conductors since it leaves only a very small air gap in the insulation, but other methods can also be used. A conductor wrapped with insulating material is placed in a tank, which is then subjected to a vacuum. Anaerobic resin usually at least about 3.1Kg/cm
(45 psi), preferably about 6.3 to about 7 Kg/cm ² (about 90 to about
into a tank under pressure (100psi). The anaerobic curing resin should be completely impregnated into the insulation so that there are no air bubbles. Typically, the insulation material contains from about 5% to about 35% by weight anaerobic resin, based on the weight of the insulation material. However, from about 20% to about 30% by weight is preferred. Excess resin is removed from the insulated conductor and the resin is cured by contacting it with an effective amount of oxygen-free gas to inhibit curing. The curing is carried out in a tank, for example, a tank 10, which is separate from the bath (tank) 7 of the anaerobic resin 8, as shown in FIG. Nitrogen, carbon dioxide, or mixtures of these two gases are preferred because they are inexpensive, safe, and easy to handle, although other inert gases other than oxygen can also be used. When using nitrogen to cure acrylic resins, it has been found that a nitrogen flow rate of about 6 to about 20 pm (l/min) provides optimum curing speed of the resin. "Embodiments of the Invention" Next, the present invention will be explained with reference to examples. Example 1 The table below lists various anaerobic resin compositions that were prepared for testing gel time and storage stability.

【table】

Table: Samples of the above resins were limited to approximately 50 g due to the high calorific value generated during curing. Storage stability testing, which measures the storage time before visual gelation occurs, was conducted on approximately 50 g samples of resin stored in 4 ounce glass jars or polyethylene containers. The samples were stored in the dark as the effect of laboratory fluorescent lighting on the stability of the resin is unknown. Periodically samples were examined for gelation time under _N2 flow to determine whether curing reactivity remained during storage. Gel time measurements (ie, the time required for visual gelation to occur) were made on 10 g samples in 5 cm (2 inch) diameter aluminum dishes.
It has been found that normal laboratory vacuum levels are insufficient to gel the sample in a reasonable amount of time.
However, rapid gelation could be achieved by placing the sample in a desiccator and passing nitrogen through the desiccator. The table below shows the results of testing Resin 10. Surface curing conditions Gelation time (25℃) Air 48 hours _N2 flow rate [13 l/min (lpm)] 30-60 minutes Vacuum 24 hours At the end of 24 hours, a very small amount of gel (approximately 7
%) was observed at the bottom of the aluminum pan of the sample in vacuum. The table below gives the results of similar tests performed on Resin 9. Surface curing conditions Gelling time (25℃) CO ₂ flow rate [13 l/min (lpm)] 20 minutes N ₂ [3.5 Kg/cm ² (50 psi) static pressure] 7 to 8 hours Air flow rate [13 l/min (lpm) ] > 2 days O ₂ flow rate [13 l/min (lpm)] > 2 days CO ₂ pressurized to 3.5 Kg/cm ² (50 psi) also produced rapid cure. Static nitrogen or carbon dioxide under pressure cured more slowly than flowing nitrogen or carbon dioxide at atmospheric pressure, but required less gas. The effect of nitrogen flow rate was investigated for Resin 9 using a similar procedure. The results are listed in the table below. Surface flow rate [l/min (lpm)] Gelling time (hour) 1.62 7.5 3.25 4.0 6.50 2.0 13.0 1.5 20.0 3.0 26.0 4.0 The table above shows that for rapid curing at a pressure of about 1 atm, approximately 6"l/min. It can be seen that flow rates between 20 liters per minute (lpm) and about 20 liters per minute (lpm) are critical. Example 2 Power factor data were obtained for mica composites impregnated with Resins 8 and 9, the most promising anaerobic resins.
Sample A is "coarse" mica paper ["cogemica", trade name,
Sold by cogebi company] [10cm x 10cm
(4 inches x 4 inches)] by brushing anaerobic resin on one piece to a thickness of approximately 0.5 mm (20 mils); (8 inch), diameter 12.5 mm (0.5 inch)] by brushing the anaerobic resin onto a polyester-impregnated mica tape wrapped six layers thick (i.e., three layers coated with half-width wraps). Two types of composite samples were prepared. It was observed that the anaerobic resin was very fluid (<3.0 cps) and therefore penetrated these mica products quickly and generally completely. These samples were gelled under _N2 flow (13.0 l/min) at room temperature. It was noted that the copper tube samples gelled quickly (ie, <30 minutes) under these conditions. To determine the extent of curing of the anaerobic resins in these composites and whether post-treatment of these materials was required, one set of these samples was baked at 135°C for 4 hours after initial room temperature curing. . Comparing the electrical data obtained from these two sets of samples appeared to indicate whether additional heat treatment was required to fully cure these anaerobic materials. Power factor measurements were recorded at 25°C and 150°C. Copper tube samples were tested at 1 KV at the above two temperatures to evaluate the effect of voltage on the power factor of these mica composites.
Measurements were also made at 1.5KV and 2KV. Sample B Power factor data obtained for copper tubes wrapped with mica tape and impregnated with the two anaerobic resins described above are listed in the table below.

Table Results for Resin 9 at 150°C showed that the sample that was not heat treated after initial curing had a slightly higher power factor value than the heat treated sample. However, both samples were 25
℃ showed similar power factor. In the case of resin 8, the sample with additional heat treatment is
At 150°C, the power factor was slightly higher than that of the sample without additional curing. However, the values at room temperature were the same for both samples. Based on these data it is difficult to determine whether additional post-heat curing treatments are necessary to achieve complete curing of these anaerobic materials. However, it is important to note that all four samples exhibited very similar room temperature power factor values. Although no attempt was made to identify the optimal mica tape for these anaerobic impregnants, it appears that the power factor values for these composites using Sample B mica tape are not excessively high. 150℃, 2KV
These values of 32-37% are unacceptably high for high voltage applications, but are suitable for insulation of low voltage equipment (e.g. <13.8 KV). Dielectric strength measurements were performed on mica composites made using Sample A impregnated with Resin 8. At room temperature in an aliphatic hydrocarbon transformer oil marketed by Westinghouse Electric Corporation under the trade name "WEMCO C".
The above samples were tested using a voltage ramp rate of 1 KV/sec. The power factor values and dielectric strength obtained for Sample A composite using Resin 10 are summarized in the table below.

Table: Again there appears to be an interesting difference between the samples with additional heat treatment and those without.
The power factor of the room temperature cured sample measured at 150 °C is very low compared to the others. The reasons for these differences are not clear at this time, but both samples are believed to have acceptably low power factor and permittivity values for insulation up to voltages of about 13.8 KV. The table below shows the dielectric strength for the two samples used in the table above. Measurement was carried out at 25℃ using "WEMCO
C' oil at a _N2 flow rate of 13.0 l/min and using a voltage ramp rate of 1 KV/sec. Both composite samples used in the power factor measurements described above were used and heated at 150° C. for 1 hour prior to dielectric strength measurements.

[Table] Samples with additional curing at high temperatures appear to have slightly higher dielectric strength than samples cured at room temperature.
However, both composites appear to have higher dielectric strength than epoxy resin impregnated mica of similar thickness. For the anaerobic resin sample of this invention: 280×10 ² ~
Typical dielectric strength values for epoxy mica composites are 160 x 10 ² to 240 x 10 ² volts ^/ mm (400 to 600
volt/mil). Example 3 To illustrate the importance of curing these resins under a flow of _N2 , the following experiment was performed. Four copper tubes were wrapped with Sample B mica tape as previously described. One set (2) of these samples was impregnated with Resin 5 and the others with Resin 8. One of each set is
After curing for 32 hours in a flow of _N2 (flow rate 13 lpm), both sets were left in air for 2 weeks. The curing conditions and resin retention for each of these samples are listed in the table below.

[Table] The resin was stored in polyethylene bottles at room temperature for 2 months before use. Resin efflux from samples cured under _N2 was found to be negligible. Next, the power factor of these four samples was measured at 25°C and 1KV. The results are listed in the table below.

Table: Samples B2 and B3 cured in a _N2 stream showed much lower power factor values than the samples left in air. This is not too surprising since the latter two samples were very sticky even after two weeks. the other one is N ₂
After a few hours inside, it became hard and dry to the touch. To explain the lack of curing in samples B1 and B4, all four samples were post-cured at 150°C for 3 days;
Power factor was remeasured at 25°C and 150°C. At room temperature these four samples gave similar values of 1.2% to 1.8%, and at 150°C they gave similar values of 23.1% to 30.2%. This therefore indicates that samples aerated with a stream of N ₂ harden more completely than those left in air. No additional heat treatment of the resin appears to be necessary for typical Class F motors. This is because the operating temperature of the motor is high enough to effect complete curing of the resin, so that complete curing is achieved after the coils are wound into the stator. Winding a partially cured coil (assuming the resin is non-viscous) may be advantageous since the mica insulation still retains a significant degree of flexibility. This is because coils are often hard and difficult to wind without cracking the insulation. [Advantageous Effects of the Invention] An advantage of the present invention is that the resin can be cured at room temperature, so that conductors conventionally used as coils in generators and motors are wrapped with mica tape and then coated with mica tape to support the brittle mica tape. After wrapping the insulated conductor with bonding glass tape and placing it in a vacuum and then placing it in the resin under pressure to impregnate the insulated conductor with resin, the resin-impregnated conductor is removed from the resin and the resin is placed in an oven. A problem encountered in the case of insulating operations using vacuum heated impregnation (VPI), where the copper of the coil had to be heated together with the resin, which required a large amount of energy, and the thermal curing of the resin This avoids the problem of resin flowing out into the resin, and mechanical stress caused by the conductor (copper) expanding during heating and curing the resin and then contracting the copper when cooled, except in the case of high voltage. It is possible to obtain electrical properties equivalent to those of currently used thermosetting resins. Also, unlike electron beam curing resins and ultraviolet curing resins, it can be cured to a depth of 15.2 mm or more.

[Brief explanation of the drawing]

FIG. 1 is a partial isometric view of an insulated conductor impregnated with an anaerobic resin, and FIG. 2 is an illustration of a continuous coating system for electrical wire using the cured resin system of the present invention.
In the diagram: 1... Conductor, 2... Mica tape insulation, 3...
Organic woven tape insulation material, 4... Anaerobic resin, 5...
... Conductor, 6 ... Capstan, 7 ... Anaerobic resin bath, 8 ... Anaerobic resin, 9 ... Sheave, 10 ... Sealed tank (tank), 11 ... (Inert gas introduction) conduit, 12...Sheave, 13...Capstan.

Claims (1)

[Scope of Claims] 1 (a) A conductor used as a coil in an electrical device is made of an insulating material, an insulating material reinforced with an impregnated reinforcing material, or an insulating material covered with a reinforcing material. or an insulating material reinforced with an impregnated reinforcement and covered with a reinforcement, and then (b) after placing the coated conductor in a vacuum, (c ) embedding the coated conductor in an anaerobically curable insulating resin in an oxygen-containing atmosphere; (d) pressurizing the resin in the presence of oxygen; and (e) removing the conductor from the resin in the presence of oxygen; (f) Vacuuming of conductors for use as coils in electrical equipment, consisting of placing a conductor with a coating saturated with an anaerobically curable insulating resin into a resin curing zone in an oxygen-free gaseous atmosphere until said resin is cured. - Pressurized insulation method. 2. The method of claim 1, wherein the insulating material is a mica tape or a mica tape impregnated with a polymer co-reactive with the anaerobic resin. 3. The method according to claim 1, wherein the reinforcing material covering the conductor is a bonding tape containing organic fibers. 4. The method of claim 1, wherein the oxygen-free gas atmosphere in the resin curing zone of step (f) is nitrogen or carbon dioxide or a mixture thereof. 5. The method according to claim 1, 2, or 3, wherein the anaerobic curable resin is an acrylic resin. 6. The method according to any one of claims 1 to 5, wherein the insulating material is mica and the conductor is copper. 7 Any one of claims 1 to 6, wherein the pressure in step (d) is 3Kg/cm ² to 7Kg/cm ²
The method described in section. 8. Claims in which the coated conductor in step (a) is an electric wire, which is passed continuously through an anaerobic curable resin in step (c) and passed through an oxygen-free gas atmosphere in step (f). The method described in paragraph 1. 9 Any one of claims 1 to 7, wherein the conductor is a motor or a generator coil.
The method described in section. 10. The method according to any one of claims 1 to 9, wherein the anaerobic curable insulating resin is a solvent-free resin. 11. The method according to any one of claims 1 to 10, wherein the anaerobic curable insulating resin contains an accelerator. 12. The method of claim 11, wherein the accelerator is benzoic acid sulfimide.