Patent Application
20190149008
The present invention relates to an electrical insulating structure producing method, an electrical insulating structure, and a rotating electrical machine.
When an unequal electric field portion occurs due to application of an electric field to an insulator, and the electric field at that portion exceeds an insulation-breakdown limit voltage, a local breakdown is caused there. When the local breakdown progresses dendritically, an electric tree is generated. The electric tree is believed to be generated by starting from a high electric field concentration parts such as an air gap or foreign matters between an electrode and an insulator, foreign matters, projections and voids in an insulator.
In recent years, the use of inverters have been prevailing. In an inverter-driven motor, the lifetime of an insulating material of a coil conductive wire may be significantly reduced when the motor is used in a state where an impulse voltage including inverter surge repeatedly acts. Therefore, for example, such situation occurs, in which insulation for normal rated voltage 6.6 kV is forced to be used for an inverter-driven motor for rated voltage 3.3 kV.
As an example of an electrical insulating structure for a conductor used in a rotating electrical machine, a coil conductor is typically covered with an insulator having an insulating material. Such a conductor easily reaching high temperatures often has a mica electrical insulating structure using mica which is a kind of silicate minerals as an insulating material of high insulation class capable of withstanding comparatively high temperatures.
When the electric tree progresses, the mica electrical insulating structure may be broken. To understand how the electric tree is generated and how it progresses is extremely important to prevent generation and progress of the electric trees and to maintain the integrity of the rotating electrical machine.
As for the integrity of the insulating material, for example, IEC (International Electrotechnical Commission) is preparing for enactment of international standards prescribing a new insulation test method for accident prevention.
Patent Document 1: U.S. Published Application No. 2015/0101845-A1
For example, the insulation lifetime of a formed-wound electrical motor for high voltage is significantly influenced by a main insulation and a turn insulation which are disposed inside a stator core. In such main insulations and turn insulations, the mica electrical insulating structure is often used.
Further, the mica electrical insulating structure as the main insulation is formed, in most cases, by impregnating a mica insulating tape with epoxy resin. The mica insulating tape is composed of mica and an epoxy glass layer. The mica insulating tape thus configured is wound around a coil conductor and then impregnated with the epoxy resin, whereby insulation treatment by the mica electrical insulating structure is performed (Refer to Patent document 1).
It was experimentally confirmed that the path of the electric tree in the thus configured mica electrical insulating structure did not penetrate a mica insulating layer but was formed on the epoxy glass layer side outside the mica insulating layer. That is, a weak point in the main insulation was found to exist in the epoxy glass layer.
The present invention has been made based on the above findings, and an object thereof is to suppress the progress of the electric tree in the electrical insulating structure.
According to the present invention, there is provided a producing method for an electrical insulating structure that covers an outer surface of a to-be-insulated object, the method comprising: a taping step of winding a main insulation tape on the outside of the to-be-insulated object to forma main insulated part; a vacuum drawing step, which is performed after the taping step, of vacuum drawing the tape-wound to-be-insulated object; and an impregnation step, which is performed after the vacuum drawing step, of injecting a nanoparticle-containing impregnating macromolecular polymer in which nanoparticles have been kneaded to impregnate the main insulated part therewith.
According to the present invention, there is provided an electrical insulating structure that covers an outer surface of a to-be-insulated object to electrically insulate the to-be-insulated object, the structure comprising: a main insulation layer extending along a surface of the to-be-insulated object; a fiber reinforcement part extending along the main insulation layer; and a macromolecular polymer part formed in the fiber reinforcement part so as to join the main insulation layer and the fiber reinforcement part, wherein nanoparticles are scattered in the macromolecular polymer part.
According to the present invention, there is provided a rotating electrical machine comprising: a rotor having an axially extending rotor shaft and a rotor core attached to radially outside the rotor shaft; a stator having a hollow cylindrical stator core disposed radially outside the rotor core so as to be spaced therefrom and stator winding conductors provided in a plurality of slots formed along an inner surface of the stator core with circumferential intervals therebetween and extending up to axial both ends of the stator core and axially outside the stator core; two bearings axially rotatably supporting the rotor shaft at both sides of the rotor shaft with the stator core axially sandwiched therebetween; a frame housing the rotor core and the stator therein; and an electrical insulating structure applied to the stator winding conductors so as to electrically insulate the stator winding conductors, wherein the electrical insulating structure includes: a main insulation layer extending along a surface of the to-be-insulated object; a fiber reinforcement part extending along the main insulation layer; and a macromolecular polymer part formed in the fiber reinforcement part so as to join the main insulation layer and the fiber reinforcement part, wherein nanoparticles are scattered in the macromolecular polymer part.
Hereinafter, with reference to the accompanying drawings, an electrical insulating structure producing method, an electrical insulating structure and a rotating electrical machine according to embodiments of the present invention will be described. The same or similar portions are represented by the same reference symbols and will not be described repeatedly.
The followings exemplify the cases where an electrical insulating structure is applied to stator winding conductors of a rotating electrical machine, to-be-insulated objects or the objects to be insulated are not limited to the stator winding conductors. That is, it is applicable to any conductors as long as they have a structure where its outer surface is covered by the electrical insulating structure.
The rotor 10 has a rotor shaft 11 extending in its longitudinal direction and a rotor core 12 attached to radially outside the rotor shaft 11. The rotor shaft 11 is rotatably supported at both axial sides thereof by bearings 5. Each of the bearings 5 is stationarily supported by each of the bearing brackets 7.
The stator 20 has a stator core 21 disposed radially outside the rotor core 12 so as to be spaced therefrom and stator windings 22 penetrating inside the stator core 21.
A plurality of stator slots (not illustrated) are formed along the inner surface of the stator core 21 with circumferential intervals therebetween and extend up to axially both ends of the stator core 21. Conductors 24 (
The plurality of stator winding conductors 24 constituting the stator winding 22 form a laminated conductor 23. Specifically, seven conductors 24 are arranged in one column and two columns form the laminated conductor 23 by fourteen conductors 24 in total. The number of laminated layers and the number of columns mentioned here are merely illustrative, and any number of the conductors 24 may be arranged in one or three or more columns. Each stator winding conductor 24 is applied with a turn insulation 25 provided outside thereof. Accordingly, the outer surface of the laminated conductor 23 is covered by the turn insulation 25.
A main insulation tape 40 serving as a main insulation is wound outside the laminated conductor 23 applied with the turn insulation 25 to form a main insulated part 49 outside the laminated conductor 23, whereby a tape-wound conductor 50 is obtained.
The width of the main insulation tape 40 is assumed to be W. The main insulation tape 40 is helically wound as viewed in the longitudinal direction of the laminated conductor 23. A winding method in this case is a half-wrap method. Specifically, the helical pitch is W/2 which is half the width W of the main insulation tape 40. In other words, the main insulation tape 40 is wound so as to overlap, by half the width, the main insulation tape 40 of the previous turn. However, the winding method is not limited to the half-wrap method. For example, the width of the overlap may be changed. Further, the main insulation tape 40 may be wound such that adjacent ones are positioned without any space between them. In this case, in second winding or in winding secondly, the main insulation tape 40 is wound shifted in the longitudinal direction by half of the width thereof.
After finishing the first winding of the main insulation tape 40 in the longitudinal direction of the laminated conductor 23, the second winding is performed on the first winding, with the result that the main insulation tape 40 has a layered structure. The number of times of the winding of the main insulation tape 40 is not limited to two and may be three or more or one and is determined according to insulating performance required.
Meanwhile, there may be a case where the stator winding conductors 24 are individually applied with insulation treatment and mica insulation treatment is applied outside the insulated stator winding conductors 24.
The material of the main insulation layer 41 is, e.g., mica, asbestos, porcelain, or the like. The material of the fiber reinforcement part 42 is, e.g., glass fiber or the like, and is generally woven in a mesh pattern. The joining macromolecular polymer 43 is, e.g., unsaturated polyester resin or epoxy resin.
The thickness of the main insulation layer 41 is, e.g., about 100 μm. The thickness of the fiber reinforcement part 42 is smaller than that of the main insulation layer 41 and is, e.g., about 30 μm. While the fiber reinforcement part 42, the joining macromolecular polymer 43, and the main insulation layer 41 are illustrated as the constituent elements of the main insulation tape 40 in
The main insulation tape 40 is wound with the main insulation layer 41 side facing the to-be-insulated object and the fiber reinforcement part 42 being outside.
First, taping is applied around the laminated conductor 23 using the main insulation tape 40 (step S01). As a result, the tape-wound conductor 50 (
The stator windings 22 are formed by connecting the tape-wound conductors 50 (
Then, the windings-incorporated object 90 is subjected to vacuum drawing (step S03).
A macromolecular polymer supply valve 63a on a macromolecular polymer supply pipe 63 and a vacuum exhaust valve 62a on a vacuum exhaust pipe 62 are closed to bring the impregnation container 61 into a sealed state. After that, the vacuum exhaust valve 62a on the vacuum exhaust pipe 62 connected to, e.g. , a vacuum pump (not illustrated) is opened to draw gas in the impregnation container 61. As a result, spaces in the main insulation tape 40 of the tape-wound conductor 50 in the windings-incorporated object 90 housed in the impregnation container 61 are also subjected to vacuum drawing.
Then, a nanoparticle-containing impregnating macromolecular polymer 47 with which nanoparticles have been kneaded is injected and the windings-incorporated object 90 is impregnated with it (step S03).
Specifically, the vacuum exhaust valve 62a on the vacuum exhaust pipe 62 is closed after the impregnation container 61 is subjected to vacuum drawing in step S03. Then, the macromolecular polymer supply valve 63a on the macromolecular polymer supply pipe 63 is opened to supply the nanoparticle-containing impregnating macromolecular polymer 47 into the impregnation container 61. The nanoparticle-containing impregnating macromolecular polymer 47 is supplied until the windings-incorporated object 90 is sufficiently impregnated with the nanoparticle-containing impregnating macromolecular polymer 47.
The nanoparticle-containing impregnating macromolecular polymer 47 has been kneaded with nanoparticles. Examples of the nanoparticle include silicon dioxide (SiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), boron nitride (BN), and carbon nanotube (CNT).
Generally, the nanoparticles are said to include particles having a diameter of up to about 100 nm. The nanoparticles used in the present embodiment are assumed to be particles having a diameter of 100 nm or less, i.e., about several tens of nm. It is considered that the following effects cannot be obtained if particles having a diameter of about several hundreds of nm exceeding 100 nm are used.
Particles having a diameter of 100 nm or less maybe produced by chemical growth from finer ones. Alternatively, particles having a diameter exceeding 100 nm may be pulverized to produce particles having a diameter of 100 nm or less. Further, surface modification may be applied so as to prevent particle aggregation in the nanoparticle-containing impregnating macromolecular polymer 47.
Hereinafter, a particle having a diameter of 100 nm or less is referred to as a nanoparticle.
When a state is reached where the windings-incorporated object 90 is sufficiently impregnated with the nanoparticle-containing impregnating macromolecular polymer 47, pressurized gas 65 is supplied from the macromolecular polymer supply pipe 63 into the impregnation container 61 to pressurize the impregnation container 61. For example, inert gas having no reactivity with the nanoparticle-containing impregnating macromolecular polymer 47 is used as the pressurized gas 65.
As a result, the nanoparticle-containing impregnating macromolecular polymer 47 permeates the main insulation tape 40 applied around the laminated conductor 23, causing the main insulation tape 40 to be impregnated with the nanoparticle-containing impregnating macromolecular polymer 47 to thereby form a macromolecular polymer part 45 (
Then, the nanoparticle-containing impregnating macromolecular polymer 47 is solidified (step S05). Specifically, the windings-incorporated object 90 is taken out of the impregnation container 61, and the macromolecular polymer part 45 (
The electrical insulating structure 30 has the main insulation layer 41 which is the main insulating part of the main insulation tape 40 (
In
In each of the taping layers A and B, the main insulation layers 41 disposed adjacent to each other overlap each other by half the width along the longitudinal direction of the laminated conductor 23. This is a result of the way of winding the main insulation tape 40 described above.
Nanoparticles 48 contained in the nanoparticle-containing impregnating macromolecular polymer 47 are scattered in the macromolecular polymer part 45 around the main insulation layer 41.
A test was performed to confirm how the electric tree progresses in the presence of the nanoparticles. The results of the test will be described below.
A plurality of the main insulation layers 41 are laminated so as to be almost parallel with each other. The fiber reinforcement part 42 and the macromolecular polymer part 45 are provided between the adjacent main insulation layers 41.
The thickness of each main insulation layer 41 is 100 μm to 140 μm, and the thicknesses of each layer of the fiber reinforcement part 42 and each layer of the macromolecular polymer part 45 are both 10 μm to 40 μm. However, as described above, in
A first test system was set, in which a needle electrode 71 was inserted into substantially the center position of the first test body 70 in a plan view. In this system, an alternating current of 50 Hz was applied between the needle electrode 71 and a grounding plate 72, and a partial discharge starting voltage was measured. After measuring of the partial discharge starting voltage, the applied voltage was boosted at a rate of 600 V/sec until occurrence of the dielectric breakdown of the sample.
The results of the test in the first test system using the first test body 70 reveal that a resin part in the fiber reinforcement part 42 between the adjacent main insulation layers 41 is weak.
Like the first test body 70, a second test body 70a simulates a state where a plurality of mica tapes are laminated. The material of the main insulation layer 41 is mica, that of the fiber reinforcement part 42 is glass fiber, and that of the macromolecular polymer part 45 is epoxy resin. The epoxy resin contains the nanoparticles in some cases and does not contain them in the other cases.
A plurality of the main insulation layers 41 are laminated so as to be almost parallel with each other. The fiber reinforcement part 42 and the macromolecular polymer part 45 are disposed between the adjacent main insulation layers 41. The grounding plate 72 is disposed at the end portions of the main insulation layer 41 and the fiber reinforcement part 42. The needle electrode 71 is inserted into an area including the fiber reinforcement part 42 and the macromolecular polymer part 45 between the adjacent main insulation layers 41. The width W of the grounding plate 72 is about 4 mm, and the depth thereof is about 25 mm. The distance D between the needle electrode 71 and the grounding plate 72 is about 3 mm.
In the test, the values of the time until the occurrence of dielectric breakdown under a condition that a voltage of 15 kV are maintained after an increase in the voltage from 1 kV to 15 kV by 1 kV steps was compared between two cases. In the first case, nanoparticles were absent in the macromolecular polymer part 45. In the second case, the nanoparticles were present. In the test results, the time was about 1.9 hours in the first case where nanoparticles were absent, while the time was three weeks or more in the second case where the nanoparticles were present. In the second case, the average particle diameter of the nanoparticles was 10 nm to 20 nm, and the mixture ratio of the nanoparticles was 10 wt %.
As described above, when the nanoparticles are mixed in the macromolecular polymer part 45, electrical insulation lifetime is significantly prolonged.
Further, it is known that heat conductivity and mechanical strength increase when the nanoparticles are mixed in the macromolecular polymer part 45.
For example, the heat conductivity is, e.g. , about 0.25 W/m·K when the nanoparticles are not mixed in the macromolecular polymer part 45, while it increases up to, e.g., about 0.40 W/m·K when mixed. As a result, heat radiation effect can be made higher, allowing more current to flow, which in turn can enhance electrical power density, i.e., electrical power per unit volume.
Further, the increase in the mechanical strength eliminates the conventional need for a temporary reinforcement for fixing the windings, thereby improving efficiency of assembly work.
As described above, according to the present embodiment, the propagation of the electric tree in the electrical insulating structure can be suppressed to thereby enhance electrical power density and improve the efficiency of assembly work.
While the embodiment of the present inventions has been described, the embodiment has been presented by way of example only, and is not intended to limit the scope of the invention. For example, although the main insulation tape is wound by the half-wrap method in the above embodiment, the present invention is not limited thereto. For example, a winding method in which the end portions of the main insulation tape are adjacent in the longitudinal direction may be adopted.
Furthermore, the above-described embodiments may be put to use in various different ways and, if appropriate, any of the components thereof may be omitted, replaced or altered in various different ways without departing from the spirit and scope of the invention.
Therefore, all the above-described embodiments and the modifications made to them are within the spirit and scope of the present invention, which is specifically defined by the appended claims, as well as their equivalents.
The present application is a continuation application of International Application No. PCT/JP2016/003162 filed on Jul. 1, 2016, the entire content of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2016/003162 | Jul 2016 | US |
| Child | 16227904 | US |
