CN116998091A

CN116998091A - Stator and rotating electrical machine having the same

Info

Publication number: CN116998091A
Application number: CN202180095387.1A
Authority: CN
Inventors: 村木孝仁; 山崎慎司; 岩城源三
Original assignee: Hitachi Astemo Ltd
Current assignee: Hitachi Astemo Ltd
Priority date: 2021-03-18
Filing date: 2021-08-24
Publication date: 2023-11-03
Also published as: WO2022195916A1; JP7460571B2; JP2022143772A

Abstract

The invention is a stator for a rotating electrical machine, comprising a stator core and a coil, the coil having a plurality of phase windings, lead wires, and neutral points for electrically connecting the plurality of phase windings, the windings including conductors, and first and second insulating films covering the conductors, the second insulating film having higher surge resistance than the first insulating film, the second insulating film covering the conductors in a range of 20 to 50% of the total length of the windings on the neutral point side. Thus, dielectric breakdown can be prevented in a specific range where the potential difference becomes large in the windings of the coil constituting the stator.

Description

Stator and rotating electrical machine having the same

Technical Field

The present invention relates to a stator and a rotating electrical machine having the same.

Background

In recent years, with the development of electric motor vehicles, high output density is demanded for electric devices, particularly rotating electric machines. The high voltage, which is one of the methods for increasing the output density, is being advanced by various automobile manufacturers. In order to cope with this, various stators having excellent insulation reliability corresponding to a high voltage have been studied in rotating electric machines.

For example, patent document 1 discloses a technique for achieving both downsizing of a rotary electric machine and high voltage and high output by providing a structure in which the thickness of an insulating layer or an insulating material is different between a slot portion and a coil end portion.

Patent document 2 discloses a technique for securing insulation performance between a joint portion and an adjacent segment conductor in a case where insulation resistance is increased by thickening an insulation coating at a predetermined portion of the conductor and the segment conductors are joined to each other.

Further, as the inverter increases in speed, the speed of the increase in input voltage to the motor also increases. Since the rising speed of the input voltage is increased, a potential difference is generated even in the same coil, and thus a new problem with respect to insulation is created.

Non-patent document 1 describes a principle of generation of a surge in an inverter-driven motor, motor entry of the surge, inter-turn voltage, and the like. Non-patent document 1 describes that when a surge enters a motor coil, most of the surge voltage is applied to a first turn of the coil, the voltage rise time is sometimes 50ns or less, and adjacent turn-to-turn voltages are generated due to a difference between a voltage pulse at the first turn and a delay voltage pulse after passing through the turns.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2008-236924

Patent document 2: international application No. second, 019/107515

Non-patent literature

Non-patent document 1: IEEJ Journal, vol.126, no.7, pp.419-422 (2006)

Disclosure of Invention

Technical problem to be solved by the invention

In the techniques described in patent documents 1 and 2, the insulation properties are improved by changing the thickness of the insulating coating film. However, it is not clear as to the range in which the insulation of the coil needs to be improved, that is, which part of the windings constituting the coil needs to be improved.

As described in non-patent document 1, it is generally known to generate an adjacent inter-turn voltage, but specifically, the range in the coil where insulation measures are required due to the influence of the adjacent inter-turn voltage is not clear.

Thus, in the conventional example, it is considered that an unnecessary range is applied to the insulation countermeasure.

The purpose of the present invention is to prevent dielectric breakdown in a specific range in which the potential difference becomes large in the windings of the coil constituting a stator.

Technical proposal for solving the technical problems

The invention is a stator for a rotating electrical machine, comprising a stator core and a coil, the coil having a plurality of phase windings, lead wires, and neutral points for electrically connecting the plurality of phase windings, the windings including conductors, and first and second insulating films covering the conductors, the second insulating film having higher surge resistance than the first insulating film, the second insulating film covering the conductors in a range of 20 to 50% of the total length of the windings on the neutral point side.

Effects of the invention

According to the present invention, dielectric breakdown can be prevented for a specific range in which the potential difference becomes large in the windings of the coil constituting the stator.

Drawings

Fig. 1 is a cross-sectional view showing a rotating electrical machine according to an embodiment.

Fig. 2 is a perspective view showing a stator of the rotating electrical machine according to the embodiment.

Fig. 3 is a schematic structural view showing a coil having a star connection.

Fig. 4 is a schematic structural view showing a coil having four reciprocating windings.

Detailed Description

The present disclosure relates to a stator having a structure excellent in insulation and a rotary electric machine having the stator.

As a result of intensive studies, the inventors of the present invention have found that the potential of a coil constituting a stator is greatly different from the potential of a lead wire within a specific range from a neutral point in the winding of the coil, due to propagation delay of the potential.

From this result, it is thought that it is effective to improve the surge resistance of the insulating coating film applied to this range.

Specifically, it was found that it is preferable that the first insulating film and the second insulating film cover the conductors constituting the winding, the second insulating film has higher surge resistance than the first insulating film, and the second insulating film covers the conductor in a range of 20 to 50% of the total length of the winding on the neutral point side.

Hereinafter, an insulating film used for a winding constituting a stator of the present disclosure will be described in detail.

(Structure of insulating coating)

Among the insulating films, the first insulating film and the second insulating film each have an electrically insulating resin. Specific examples of the resin include polyvinyl formal, polyester amide, polyamide imide, polyimide, nylon, polyoxymethylene, polyphenylene sulfide, polyether ether ketone, polytetrafluoroethylene, and the like. Among them, from the viewpoints of heat resistance, processability and adhesiveness, polyesters, polyesteramides, polyamideimides and polyimides are preferable. The resin may be used alone or in a plurality of layers. The multilayer means may be any of conventional methods such as baking, multilayer extrusion, and the like, and is not particularly limited. Further, it is preferable that these resins are identical within 1 segment coil before welding. In other words, the segmented coil preferably has only one of the first insulating film and the second insulating film.

(component for improving Surge resistance)

As a method for improving the surge resistance, addition of inorganic particles and lowering of dielectric constant are mentioned.

The inorganic particles may have electrical insulation, and examples thereof include silica, alumina, mica, and the like. These may be used alone or in combination of 2 or more.

Examples of the inorganic particle addition include a method in which polyamide imide is used for the first insulating film and a method in which nano-silica particles are added to polyamide imide for the second insulating film.

The resin to be the base material may be selected from the above resin groups, and may be used alone or in a plurality of types.

Examples of the low dielectric constant include a method in which a polyamide-imide having a dielectric constant of 4 is used for the first insulating film and a method in which a polyamide-imide having a dielectric constant of 3.5 is used for the second insulating film. The combination of these resins is not particularly limited as long as the dielectric constant of the second insulating film is lower than that of the first insulating film.

(application site of second insulating coating)

The application site of the second insulating film is preferably a power supply input site, that is, a lead wire, and a portion between the lead wire and a neutral point and on a side of a surrounding winding portion constituting the surrounding winding adjacent to the neutral point, the portion having a total length of 20 to 50% with respect to the surrounding winding portion. This portion is a portion where the potential difference increases due to the rise of the pulse at the time of power supply input. In the case of forming the insulating film by baking, the thickness of the resin for improving the surge resistance of the second insulating film is preferably 5% or more and less than 100%, more preferably 20% or more and less than 60% of the entire thickness. If the thickness is less than 20%, the surge resistance may be insufficient, and if the thickness is greater than 60%, the adhesion between the conductor and the coating may be weakened. The thickness of each of the first insulating film and the second insulating film is not particularly limited as long as it is appropriate for the power supply voltage.

(Structure of rotating Electrical machine)

Next, the structure of the rotary electric machine will be described. The embodiment described below is only one example and is not limited to these examples. In the above description, as an example of the rotating electrical machine, an electric motor used in a hybrid vehicle is used. In the following description, "axial direction" refers to a direction along the rotation axis of the rotating electrical machine. Further, "circumferential" refers to a direction along the rotation direction of the rotary electric machine. The "radial direction" refers to a radial direction (radial direction) when the rotating shaft of the rotating electrical machine is the center. "inner peripheral side" means radially inner side (inner diameter side) and "outer peripheral side" means radially outer side (outer diameter side) which is the opposite direction thereof.

Fig. 1 is a cross-sectional view showing an example of a rotary electric machine according to an embodiment.

In the present figure, a rotary electric machine 10 includes a rotor 11, a stator 20, and a housing 50. The rotor 11 includes a rotor core 12 and a rotating shaft 13. The rotor 11 is provided with permanent magnets 18 and end rings (not shown). The stator 20 includes a stator core 21 (stator core).

The stator 20 having the coil 40 is fixed to the inner peripheral side of the housing 50. The rotor 11 is rotatably provided on the inner peripheral side of the stator 20. The case 50 constitutes a housing of the rotary electric machine 10, and is formed into a cylindrical shape by cutting an iron-based material such as carbon steel, casting cast steel or an aluminum alloy, or press working. The housing 50 is also referred to as a frame or a frame.

The outer peripheral side of the housing 50 is provided with a liquid cooling jacket 130. The gap provided between the inner peripheral wall of the liquid-cooled jacket 130 and the outer peripheral wall of the housing 50 is a refrigerant passage 153 for the liquid-state refrigerant 157 such as oil. The refrigerant passage 153 is configured so that no liquid leakage occurs. The liquid-cooled jacket 130 has bearings 144, 145, which can also be referred to as "bearing supports".

In the case of direct liquid cooling, the refrigerant 157 flows out from the refrigerant outlets 154, 155 to the stator 20 through the refrigerant passage 153, and cools the stator 20. Thereafter, the refrigerant 157 is temporarily stored in the refrigerant storage portion 150, and circulated by a pump provided outside.

The stator core 21 has a structure in which thin sheets of silicon steel plates are laminated.

Heat generated by the coil 40 provided in the stator 20 is transferred to the housing 50 through the stator core 21, and is transferred to the outside through the refrigerant 157 flowing through the liquid cooling jacket 130, thereby dissipating heat.

The rotor core 12 has a structure in which thin plates of silicon steel plates are laminated. The rotary shaft 13 of the rotor 11 is fixed to the center of the stator core 12. The rotary shaft 13 is rotatably supported by bearings 144 and 145 attached to the liquid cooling jacket 130. Thus, the rotor 11 rotates at a predetermined position in the stator 20 and at a position facing the stator 20.

In assembling the rotary electric machine 10, the stator 20 is inserted into the inside of the housing 50 in advance to be mounted to the inner peripheral wall of the housing 50, and then the rotor 11 is inserted into the stator 20. Next, the bearings 144 and 145 are attached to the liquid cooling jacket 130 so as to be fitted into the rotary shaft 13.

Next, the structure of the main portion of the stator 20 will be described.

Fig. 2 is a perspective view showing an example of a stator of a rotary electric machine according to the embodiment.

In the present figure, a stator 20 includes a stator core 21 and a stator coil 60. The stator coil 60 is wound around the slots 15, and a plurality of the slots 15 are provided in the inner peripheral portion of the stator core 21.

The stator 20 includes a stator core 21 and stator coils 60, and the stator coils 60 are wound around slots 15, and a plurality of slots 15 are provided in an inner peripheral portion of the stator core 21. The stator coil 60 is formed of a conductor having a substantially rectangular cross section, and has an insulating coating. In this embodiment, the conductor is formed of a copper alloy. By setting the cross-sectional shape of the conductor of the stator coil 60 to a substantially rectangular shape, the volume occupancy of the conductor in the slot 15 can be increased, and the efficiency of the rotating electrical machine 10 can be improved.

Further, the slot liners 301 are disposed in the slots 15, and the insulating paper 300 is disposed on the outer periphery of the stator core 21, so that the stator core 21 and the stator coil 60 and the like are electrically insulated and bonded reliably. The slot liner 301 is formed in a mouth shape, a B shape or an S shape to wrap copper wires.

The stator coil 60 is formed by inserting the segmented coils into the slots 15 in which the slot liners 301 are disposed and welding them. Thereafter, an adhesive varnish is impregnated in the tank 15 and heated, thereby bonding the coils. That is, the windings of the stator coil 60 are constituted by segmented coils.

The stator coil 60 has lead wires 26a, 26b, 26c and a neutral point 27. The lead wires 26a, 26b, 26c and the neutral point 27 are arranged in close proximity.

The above description has been made about a permanent magnet type rotating electrical machine, but the characteristics of the rotating electrical machine according to the present disclosure relate to coil insulation of a stator, and therefore, the rotor can be applied to induction type, synchronous reluctance type, claw pole type, and the like, in addition to the permanent magnet type. The winding system is a wave system, but any winding system having the same characteristics may be applied. The description has been given of the inner transfer type, but the same applies to the outer transfer type.

Fig. 3 is a schematic structural view showing a coil having a star connection.

As shown in the figure, the coil 40 of the stator has lead wires 26a, 26b, 26c and a neutral point 27. The outgoing lines 26a, 26b, 26c and the neutral point 27 are connected by windings of three phases. The lead wires 26a, 26b, 26c and the neutral point 27 are actually arranged in close proximity.

In the present figure, when the entire length of a line segment connecting the lead line 26a representing the U-phase winding and the neutral point 27 is 100, the winding located within the length 25 indicated by a thick solid line from the neutral point 27 is covered with the second insulating film 402. That is, in the whole winding, 25% of the range from the neutral point 27 is covered with the second insulating coating 402. On the other hand, the remaining portion of the winding shown by the broken line (75% range from the lead wire 26 a) is covered with the first insulating coating 401. The V phase and the W phase are also the same. The lead wires 26a, 26b, 26c and the neutral point 27 are also covered with the second insulating coating 402.

In addition, in the present figure, a star connection is shown, but the structure of the winding of the present disclosure is not limited thereto, and can be applied to a stator having other connection structures such as a delta connection.

In order to clarify the reciprocating structure of the winding, the coil 40 shown in the present figure is schematically represented by a structure having a lead wire 46 and a neutral point 47 for one of three phases.

In the present figure, the coil 40 has a structure including a first turn 41, a second turn 42, a third turn 43, and a fourth turn 44 from the lead wire 46 toward the neutral point 47. The turns each form a reciprocating winding.

Typically, when a pulse voltage is applied to the outlet 46, a sharp change in the current value occurs. At this time, an induced electromotive force due to inductance is generated in the windings of the coil 40. Therefore, it is difficult for the pulse voltage to propagate to a portion on the neutral point 47 side farther from the lead line 46 of the winding. Therefore, a large potential difference may occur between the lead line 46 side and the neutral point 47 side. When the lead wire 46 side is adjacent to the conductor on the neutral point 47 side, dielectric breakdown is likely to occur due to a potential difference. In the case of a pulse voltage of MHz level, the time rate of change of current becomes particularly remarkable, and the induced electromotive force tends to be large.

The present inventors have made intensive studies on the application of a pulse voltage of MHz level to a coil, and as a result, have found that the second insulating coating is preferably used to cover the entire winding in a range of 20 to 50% from the neutral point. In other words, the range covered by the second insulating coating in the surrounding winding is preferably 20 to 50% of the portion on the neutral point side in the total length of the surrounding winding.

Here, the lower limit value of the range covered by the second insulating film is based on the results of the dielectric breakdown lifetime test of examples, comparative examples, and the like described later. On the other hand, regarding the upper limit of the range, although a sufficient lifetime can be obtained if the range covered by the second insulating film is enlarged, it is needless to say that the cost is not only reduced but also the weight of the coil is reduced if the range covered by the second insulating film is enlarged to be more than necessary because inorganic fine particles or the like having a high density are added to the resin. Therefore, the upper limit of the range is preferably 50%. More preferably 40%, particularly preferably 30%. As will be described later, this is because a dielectric breakdown lifetime equivalent to that in the case of 100% coverage can be obtained even when the dielectric breakdown lifetime is set to 25%.

In fig. 4, a coil having four windings that reciprocate is shown, but in the case where the windings of the coil reciprocate eight times, it is similarly known that the range covered by the second insulating coating in the surrounding winding is preferably 20 to 50% of the portion on the neutral point side in the total length of the surrounding winding. That is, when the coil windings are eight reciprocating windings, approximately two reciprocating windings on the neutral point side thereof may be covered with the second insulating coating film.

Hereinafter, examples and comparative examples will be described.

In the stator of the embodiment and the like, the end portion of the lead wire and the neutral point, and a predetermined portion on the neutral point side of the winding (surrounding winding) constituting the coil located between the lead wire and the neutral point are covered with the second insulating coating film, and the other surrounding windings are covered with the first insulating coating film. The second insulating film is more excellent in surge resistance than the first insulating film. The thickness (film thickness) of the first insulating film and the second insulating film were equal to each other and were 70 μm.

Example 1

As the first insulating film, polyamideimide containing no inorganic fine particles is used.

In addition, as the second insulating film, polyamideimide containing nano silica particles in an amount of 60% of the total film thickness was used. That is, for a thickness of 70 μm, 28 μm was used a polyamideimide containing no inorganic particles, and 42 μm was used a polyamideimide containing inorganic particles. The range covered by the second insulating film in the surrounding winding is set to a portion (the same portion as in fig. 3) of 25% of the neutral point side in the total length of the surrounding winding.

Example 2

As the first insulating film, polyamideimide containing nano-silica particles in an amount of 20% of the total film thickness was used.

In addition, as the second insulating film, polyamideimide containing nano silica particles in an amount of 60% of the total film thickness was used. The range covered by the second insulating coating in the surrounding winding is set to a portion of 25% of the neutral point side in the total length of the surrounding winding.

Comparative example 1

In all the ranges around the winding, polyamide imide containing no nano silica particles is used as the insulating coating film. That is, the second insulating film is not used, but the first insulating film covers all the areas.

Comparative example 2

In addition, as the second insulating film, polyamideimide containing nano silica particles in an amount of 60% of the total film thickness was used. The range covered by the second insulating coating in the surrounding winding is set to a portion of 15% of the neutral point side in the total length of the surrounding winding.

(reference example)

In all the ranges around the winding, as the insulating coating film, polyamideimide containing nano silica particles in an amount of 60% of the total film thickness was used. That is, the first insulating film is not used, but the second insulating film covers all the areas.

Further, since these stators use the segment coils, the application site of the first insulating film and the application site of the second insulating film can be appropriately selected from either the segment coils having the first insulating film or the segment coils having the second insulating film at the time of core insertion, respectively, and thus can be manufactured using a conventional manufacturing apparatus.

(verification of Effect)

The stators of examples 1 and 2, comparative examples 1 and 2 and reference examples were manufactured, and the inter-wire conduction lifetime test was performed. In this test, a high-voltage pulse generator PG-W15KD produced by pulse electronics technology (Inc.) was used as a power supply, 2kV was applied to the U-phase lead wire at 500Hz, and V was grounded. In addition, the neutral point is cut off in advance.

Table 1 shows the test results.

TABLE 1

Stator	Example 1	Example 2	Comparative example 1	Comparative example 2	Reference example
						Time required for dielectric breakdown	75 hours	73 hours	48 hours	50 hours	73 hours

As is clear from the table, the time required for dielectric breakdown of the stators of examples 1 and 2 and the reference example was 1.5 times longer than that of comparative example 1 which was made of only the coil having no second insulating film excellent in surge resistance, and the insulation properties and the life were improved.

In comparative example 2, the range covered by the second insulating film was set to 15%, and therefore, the effect of improving the insulating life was insufficient as compared with examples 1 and 2 and the reference example.

Further, although a coil having a first insulating film with poor surge resistance was used as a part of the stator of examples 1 and 2, it had an equivalent dielectric breakdown life as that of the reference example made of a coil having only a second insulating film with excellent surge resistance.

Further, it was found from some experiments that even a portion where the range covered by the second insulating film was set to 20%, the second insulating film had an equivalent dielectric breakdown life to those of examples 1 and 2.

Thus, the stator and the rotating electrical machine having the stator according to the present disclosure can achieve both reduction in the amount of the insulating film used and improvement in the insulating properties, which are excellent in surge resistance at high cost.

The stator and the rotating electrical machine having the same according to the present disclosure are not limited to the above-described embodiments, and include various modifications. The above-described embodiments are described in detail for the purpose of explaining the structure of the stator and the like according to the present disclosure for ease of understanding, and are not limited to include all the configurations described. In addition, other structures may be added, deleted, or replaced to a part of the structures of the embodiments.

Description of the reference numerals

10. Rotary electric machine

11. Rotor

12. Rotor core

13. Rotating shaft

15. Groove(s)

18. Permanent magnet

20. Stator

21. Stator core

40. Coil

41. First turn

42. Second turn

43. Third turn

44. Fourth turn

46. Leading-out wire

47. Neutral point

50. Shell body

60. Stator coil

130. Liquid cooling jacket

144. 145 bearing

150. Refrigerant storage unit

153. Refrigerant passage

154. Refrigerant outlet

155. Refrigerant outlet

401. First insulating film

402. Second insulating film

300. Insulating paper

301. Groove lining

501. Adhesive varnish

157. And (3) a refrigerant.

Claims

1. A stator that constitutes a rotating electrical machine, comprising:

a stator core; and

the coil is arranged in a loop of wire,

the coil has windings of a plurality of phases, an outgoing line, and a neutral point electrically connecting the windings of the plurality of phases,

the winding includes a conductor, a first insulating film and a second insulating film covering the conductor,

the second insulating film has higher surge resistance than the first insulating film,

the second insulating film covers a portion of the total length of the winding, which is 20 to 50% of the neutral point side.

2. The stator according to claim 1, wherein,

the first insulating film and the second insulating film include any one of polyimide, polyamideimide, polyesterimide, and polyester.

3. The stator according to claim 1, wherein,

the second insulating coating film contains inorganic particles.

4. The stator according to claim 3, wherein,

the inorganic particles of the second insulating film are contained in a higher amount than the inorganic particles of the first insulating film.

5. The stator according to claim 3, wherein,

the inorganic particles comprise any one of silica, alumina, and mica.

6. The stator according to claim 1, wherein,

the windings are formed of segmented coils.

7. The stator as claimed in claim 6, wherein,

the segmented coil has only one of the first insulating film and the second insulating film.

8. A rotating electrical machine, characterized by comprising:

the stator of any one of claims 1 to 7; and a rotor.