WO2022195916A1

WO2022195916A1 - Stator and rotating electric machine having same

Info

Publication number: WO2022195916A1
Application number: PCT/JP2021/030908
Authority: WO
Inventors: 孝仁村木; 慎司山崎; 源三岩城
Original assignee: 日立Astemo株式会社
Priority date: 2021-03-18
Filing date: 2021-08-24
Publication date: 2022-09-22
Also published as: CN116998091A; JP2022143772A; JP7460571B2

Abstract

This stator constitutes a rotating electric machine and comprises a stator core and coils, wherein the coils have windings having a plurality of phases, a lead-out wire, and a neutral point to which the windings having the plurality of phases are electrically connected. The windings include a conductor and first and second insulating coats covering the conductor. The second insulating coat has higher anti-surge properties than the first insulating coat, and an area within which the second insulating coat covers the conductor is a portion of 20 to 50% of the total length of the windings on the neutral point side. This makes it possible to prevent insulation breakdown in a specific area in which the potential difference becomes larger in the windings constituting the coil of the stator.

Description

Stator and rotary electric machine having the same

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

In recent years, with the progress of electrification of automobiles, there is a demand for higher output density of electrical equipment, especially rotating electric machines. Automobile manufacturers are proceeding with increasing the voltage, which is one of the techniques for increasing the power density. In order to cope with this, various stators with excellent insulation reliability corresponding to higher voltages are being studied in rotary electric machines.

For example, Patent Literature 1 discloses a technique for realizing both miniaturization, high voltage, and high output of a rotating electrical machine by configuring the slots and coil end portions with different insulating layer thicknesses or different insulating materials. ing.

Patent Document 2 discloses a technique for increasing the insulation resistance by increasing the thickness of the insulating coating at a predetermined portion of the conductor, and ensuring the insulation performance between the joint and the adjacent segment conductor when the segment conductors are joined together. is disclosed.

In addition, due to the speeding up of the inverter, the rise speed of the input voltage to the motor is also increasing. As the rising speed of the input voltage increases, a potential difference occurs even within the same coil, which poses a new problem for insulation.

Non-Patent Document 1 describes the principle of surge generation in an inverter-driven motor, the surge entering the motor and the voltage between turns, etc. Non-Patent Document 1 describes that when a surge enters a motor coil, most of the surge voltage is applied to the first turn of the coil, that the voltage rise time may be 50 ns or less, and that the voltage pulse and the turn in the first turn It is described that a voltage between adjacent turns is generated due to a difference from the delayed voltage pulse after passage.

JP 2008-236924 A International Application No. 019/107515

In the techniques described in Patent Documents 1 and 2, the insulation is improved by changing the thickness of the insulating coating. However, the extent to which the insulation of the coil needs to be improved, that is, which part of the windings constituting the coil needs to be improved in insulation has not been clarified.

In addition, as described in Non-Patent Document 1, it is generally known that a voltage between adjacent turns is generated. has not been clarified.

Therefore, in the conventional example, it is considered that insulation measures were taken to an unnecessary extent.

The object of the present invention is to prevent dielectric breakdown in a specific range where the potential difference is large in the windings that make up the coils of the stator.

The present invention is a stator that constitutes a rotating electric machine, and includes a stator core and a coil, and the coil has a plurality of phase windings, a lead wire, and a plurality of phase windings electrically connected to each other. the winding includes a conductor, a first insulating coating and a second insulating coating covering the conductor, the second insulating coating being greater than the first insulating coating The range of the second insulating coating covering the conductor is 20 to 50% of the total length of the winding on the neutral point side.

According to the present invention, it is possible to prevent dielectric breakdown in a specific range where the potential difference is large in the windings that make up the coils of the stator.

1 is a cross-sectional view showing a rotating electric machine according to an embodiment; FIG. 1 is a perspective view showing a stator of a rotary electric machine according to an embodiment; FIG. FIG. 3 is a schematic configuration diagram showing a coil having star connection; FIG. 4 is a schematic configuration diagram showing a coil having four reciprocating windings;

The present disclosure relates to a stator having a structure with excellent insulating properties and a rotating electric machine having the same.

As a result of intensive research, the present inventors proceeded with measurements of the voltage sharing ratio of the stator, etc., and found that due to the propagation delay of the potential, in a specific range from the neutral point of the windings constituting the stator coil , that the potential is significantly different from that of the lead wire.

From this result, we came up with the idea that it would be effective to increase the surge resistance of the insulating coating applied to this area.

Specifically, of the first insulating coating and the second insulating coating covering the conductors constituting the winding, the surge resistance of the second insulating coating is made higher than that of the first insulating coating, and the second It has been found that it is desirable to cover the conductor with the insulating coating of 20 to 50% of the total length of the winding on the neutral point side.

The insulating coating used for the windings that constitute the stator of the present disclosure will be described in detail below.

(Structure of insulating coating)
Both the first insulating coating and the second insulating coating contain an electrically insulating resin. Specific examples of resins include polyvinyl formal, polyester, polyesterimide, polyamideimide, polyimide, nylon, polyoxymethylene, polyphenylene sulfide, polyetheretherketone, and polytetrafluoroethylene. Among these, polyester, polyesterimide, polyamideimide and polyimide are preferred from the viewpoint of heat resistance, workability and adhesiveness. In addition, the resin may be used singly or may be used by laminating a plurality of resins. The multi-layer means is not particularly limited, and existing techniques such as baking coating and multi-layer extrusion can be used. It is desirable that these resins are the same within one segment coil before welding. In other words, the segment coil desirably has only one of the first insulating coating and the second insulating coating.

(Component that improves surge resistance)
Techniques for improving surge resistance include adding inorganic particles and lowering the dielectric constant.

　Inorganic particles may be electrically insulating, such as silica, alumina, and mica. These may be used singly or in combination of two or more.

Examples of the addition of inorganic particles include the method of using polyamide-imide for the first insulating coating and nano-silica particle-added polyamide-imide for the second insulating coating.

The base material resin is selected from the above resin group, and may be used singly or in multiple types.

As an example of lowering the dielectric constant, there is a method of using polyamide-imide with a dielectric constant of 4 for the first insulating coating and polyimide with a dielectric constant of 3.5 for the second insulating coating. The combination of these resins is not particularly limited as long as the dielectric constant of the second insulating coating is lower than that of the first insulating coating.

(Applied portion of the second insulating coating)
The portions to which the second insulating coating is applied are the lead wire that is the input portion of the power source, and are between the lead wire and the neutral point and are adjacent to the neutral point of the encircling winding portion that constitutes the encircling winding. It is preferable that it is the side and is a portion of 20 to 50% of the total length of the winding portion. This portion is a portion where the potential difference increases due to the rise of the pulse when power is input. Further, when the insulating coating is formed by baking coating, the resin thickness that improves the surge resistance of the second insulating coating is preferably 5% or more and less than 100% of the whole, more preferably 20% or more. less than 60%. If it is thinner than 20%, the surge resistance may be insufficient, and if it is thicker than 60%, the adhesion between conductors and coatings may be weakened. Moreover, the film thickness of both the first insulating film and the second insulating film is not particularly limited as long as the film thickness is selected to be suitable for the power supply voltage.

(Configuration of rotating electric machine)
Next, the configuration of the rotating electrical machine will be described. The embodiments described below are merely examples, and are not limited to these examples. In addition, in the following description, the electric motor used for a hybrid vehicle is used as an example of a rotary electric machine. In the following description, "axial direction" refers to the direction along the rotating shaft of the rotating electric machine. Also, the “circumferential direction” refers to the direction along the rotation direction of the rotating electric machine. "Radial direction" refers to a radial direction (radial direction) around the rotating shaft of the rotating electric machine. The "inner peripheral side" refers to the radially inner side (inner diameter side), and the "outer peripheral side" refers to the opposite direction, that is, the radial outer side (outer diameter side).

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

In this figure, the rotating electrical machine 10 includes a rotor 11 , a stator 20 and a housing 50 . Rotor 11 includes rotor core 12 and 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).

A stator 20 having a coil 40 is fixed to the inner peripheral side of the housing 50 . A rotor 11 is rotatably installed on the inner peripheral side of the stator 20 . The housing 50 forms a cylindrical outer cover of the rotating electric machine 10 by cutting a ferrous material such as carbon steel, by casting cast steel or an aluminum alloy, or by pressing. The housing 50 is also called a frame or frame.

A liquid cooling jacket 130 is installed on the outer peripheral side of the housing 50 . A gap provided between the inner peripheral wall of the liquid cooling jacket 130 and the outer peripheral wall of the housing 50 is a coolant passage 153 for a liquid coolant 157 such as oil. The refrigerant passage 153 is configured so as not to leak. Liquid cooling jacket 130 has

bearings

144, 145 and may also be referred to as a "bearing bracket."

In the case of direct liquid cooling, coolant 157 flows through coolant passage 153 and flows out from

coolant outlets

154 and 155 toward stator 20 to cool stator 20 . Thereafter, refrigerant 157 is temporarily stored in refrigerant reservoir 150 and circulated by a pump installed outside.

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

The heat generated by the coils 40 installed in the stator 20 is transmitted to the housing 50 via the stator core 21, transferred to the outside by the coolant 157 flowing through the liquid cooling jacket 130, and radiated.

The rotor core 12 has a structure in which thin silicon steel plates are laminated. A rotating shaft 13 of the rotor 11 is fixed to the center of the rotor core 12 . The rotating shaft 13 is rotatably supported by

bearings

144 and 145 attached to the liquid cooling jacket 130 . As a result, the rotor 11 rotates at a predetermined position inside the stator 20 and at a position facing the stator 20 .

To assemble the rotating electrical machine 10 , the stator 20 is inserted inside the housing 50 and attached to the inner peripheral wall of the housing 50 in advance, and then the rotor 11 is inserted into the stator 20 . Next, the rotating shaft 13 is assembled to the liquid cooling jacket 130 so that the

bearings

144 and 145 are fitted.

Next, the configuration of the main part of the stator 20 will be explained.

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

In this figure, the stator 20 includes a stator core 21 and a stator coil 60. The stator coil 60 is wound around a number of slots 15 provided in the inner circumference of the stator core 21 .

The stator 20 includes a stator core 21 and stator coils 60 wound in a number of slots 15 provided in the inner periphery of the stator core 21 . The stator coil 60 is made of a conductor having a substantially rectangular cross section and has an insulating coating. In this embodiment, the conductor is made of a copper alloy. By making the cross-sectional shape of the conductors of the stator coil 60 substantially rectangular, the space factor of the conductors in the slots 15 can be improved, and the efficiency of the rotating electric machine 10 can be improved.

A slot liner 301 is provided in each slot 15, and an insulating paper 300 is provided around the outer periphery of the stator core 21 to ensure electrical insulation and adhesion between the stator core 21 and the stator coil 60 and the like. there is The slot liner 301 is formed in a square shape, a B shape, or an S shape so as to wrap the copper wire.

A stator coil 60 is formed by inserting a segmented coil into the slot 15 provided with the slot liner 301 and welding it. Thereafter, the slots 15 are impregnated with a bonding varnish and heated to bond the coils. That is, the windings of the stator coil 60 are composed of segment coils.

The stator coil 60 has lead

wires

26 a , 26 b , 26 c and a neutral point 27 . The

lead wires

26a, 26b, 26c and the neutral point 27 are arranged close to each other.

The above description is about the permanent magnet type rotating electric machine, but since the feature of the rotating electric machine according to the present disclosure relates to the coil insulation of the stator, the rotor can be not only the permanent magnet type but also the induction type. , synchronous reluctance, claw magnetic pole type, etc. Moreover, although the winding method is the wave winding method, any winding method having similar characteristics can be applied. Moreover, although the adductor type has been described, it is also applicable to the abductor type.

FIG. 3 is a schematic configuration diagram showing a coil with star connection.

As shown in this figure, the stator coil 40 has lead

wires

26a, 26b, 26c and a neutral point 27. The

lead wires

26a, 26b, 26c and the neutral point 27 are connected by three-phase windings. Moreover, the

lead wires

26a, 26b, 26c and the neutral point 27 are actually arranged close to each other.

In this figure, when the total length of the line segment connecting the lead wire 26a representing the U-phase winding and the neutral point 27 is 100, the length 25 indicated by the thick solid line from the neutral point 27 is A second insulating coating 402 covers the windings in range. That is, 25% of the entire winding is covered with the second insulating coating 402 from the neutral point 27 . On the other hand, the remaining portion of the winding indicated by the dashed line (75% range from the lead wire 26a) is covered with the first insulating coating 401. As shown in FIG. The same applies to the V phase and W phase. The

lead wires

26 a , 26 b , 26 c and the neutral point 27 are also covered with the second insulating coating 402 .

In this figure, the case of star connection is shown, but the configuration of the windings of the present disclosure is not limited to this, and can also be applied to stators having other connection structures such as delta connection. It is possible.

FIG. 4 is a schematic configuration diagram showing a coil having four reciprocating windings.

The coil 40 shown in this figure is schematically represented as having a lead wire 46 and a neutral point 47 for one of the three phases in order to clarify the reciprocating structure of the windings.

In this figure, the coil 40 has a configuration 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. Each of these turns constitutes one round trip winding.

Generally, when a pulse voltage is applied to the lead wire 46, a sharp change in current value occurs. At this time, an induced electromotive force is generated in the winding of the coil 40 due to the inductance. Therefore, it is difficult for the pulse voltage to propagate to the portion of the winding on the side of the neutral point 47 far from the lead wire 46 . Therefore, a large potential difference may occur between the lead wire 46 side and the neutral point 47 side. If the conductors on the lead wire 46 side and the neutral point 47 side are adjacent to each other, dielectric breakdown is likely to occur due to the potential difference. In the case of a pulse voltage on the order of MHz, the time rate of current change is particularly remarkable, and the induced electromotive force tends to increase.

The present inventor conducted extensive experimental studies on applying a pulse voltage on the order of MHz to a coil, and found that 20 to 50% of the entire winding from the neutral point can be covered with the second insulating coating. I have come to the conclusion that it is desirable. In other words, it is desirable that the area covered by the second insulating coating in the round winding is 20 to 50% of the total length of the round winding on the neutral point side.

Here, the lower limit of the range covered by the second insulating coating is based on the results of dielectric breakdown life tests in Examples, Comparative Examples, etc. described later. On the other hand, regarding the upper limit of the range, it goes without saying that if the range covered by the second insulating film is widened, a sufficient life can be obtained. If the range covered with the insulating film is made wider than necessary, it is against not only the cost but also the weight reduction of the coil. Therefore, the upper limit of the range is preferably 50%. More preferably, it is 40%, and particularly preferably 30%. This is because, as will be described later, even at 25%, the same level of dielectric breakdown life as in the case of 100% coverage was obtained.

FIG. 4 shows a coil having four round trip windings, but in the case where the coil has eight round trip windings, similarly, the range covered with the second insulating coating in the round winding is 20 to 50% of the total length of the center point side is desirable. That is, if the winding of the coil has eight reciprocations, it is sufficient to cover about two reciprocations of the windings on the neutral point side with the second insulating coating.

Examples and comparative examples will be described below.

In the stators of the embodiments, the ends of the lead wires and the neutral point, and of the windings (circular windings) forming the coil located between the lead wires and the neutral point, the neutral point side A predetermined portion is covered with a second insulating coating, and the rest of the circular winding is covered with a first insulating coating. The second insulating coating has better surge resistance than the first insulating coating. The thickness (film thickness) of the first insulating coating and the second insulating coating is equal to 70 μm.

Polyamide-imide containing no inorganic fine particles was used as the first insulating coating.

On the other hand, as the second insulating coating, 60% of the total film thickness used polyamide-imide containing nanosilica fine particles. That is, for a thickness of 70 μm, a polyamide-imide containing no inorganic particles is used for a thickness of 28 μm, and a polyamide-imide containing inorganic particles is used for a thickness of 42 μm. The area covered with the second insulating film in the round winding was set to 25% of the entire length of the round winding on the neutral point side (the same portion as in FIG. 3).

As the first insulating coating, 20% of the total film thickness used polyamide-imide containing nanosilica fine particles.

On the other hand, as the second insulating coating, 60% of the total film thickness used polyamide-imide containing nanosilica fine particles. The area covered by the second insulating film in the round winding was set to 25% of the entire length of the round winding on the neutral point side.

(Comparative example 1)
Polyamide-imide containing no nanosilica fine particles was used as an insulating coating in the entire area of the winding wire. In other words, the entire range was covered with the first insulating coating without using the second insulating coating.

(Comparative example 2)
Polyamide-imide containing no inorganic fine particles was used as the first insulating coating.

On the other hand, as the second insulating coating, 60% of the total film thickness used polyamide-imide containing nanosilica fine particles. The area covered with the second insulating film in the round winding was set to 15% of the total length of the round winding on the neutral point side.

(Reference example)
Polyamide-imide containing nanosilica fine particles in 60% of the total film thickness was used as the insulating coating in the entire range of the winding wire. That is, the entire range was covered with the second insulating coating without using the first insulating coating.

In addition, since these stators use segment coils, the portion to which the first insulating coating is applied and the portion to which the second insulating coating is applied are, respectively, the segment coil having the first insulating coating and the second insulating coating. Since either one of the segment coils having the insulating coating can be appropriately selected when inserting the core, it is possible to manufacture using conventional manufacturing equipment.

(Verification of effect)
A line voltage application life test was performed on the manufactured stators of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example. In this test, a high-voltage pulse generator PG-W15KD manufactured by Pulse Electronic Technology Co., Ltd. was used as a power supply, 2 kV was applied to the U-phase lead wire at 500 Hz, and the V-phase was grounded. In addition, the neutral point was cut in advance.

Table 1 shows the test results.

From this table, it can be seen that the stators of Examples 1 and 2 and the reference example take 1 time longer for dielectric breakdown than Comparative Example 1, which is manufactured only with a coil that does not have a second insulation coating with excellent surge resistance. 0.5 times or more, and it can be seen that the life is improved in terms of insulation.

In addition, in Comparative Example 2, since the area covered by the second insulating coating is 15%, compared to Examples 1 and 2 and the Reference Example, the effect of improving the insulation life is not sufficient.

Furthermore, although the stators of Examples 1 and 2 partially used the coil having the first insulation coating with poor surge resistance, only the second insulation coating with excellent surge resistance was used. It has a dielectric breakdown life equivalent to that of the reference example produced with the coil having

In addition, it has been found from several experiments that even if the area covered by the second insulating film is 20%, the dielectric breakdown life is equivalent to that of Examples 1 and 2.

As described above, the stator according to the present disclosure and the rotary electric machine having the same can reduce the amount of the high-cost, surge-resistant insulating coating and improve the insulating properties.

It should be noted that the stator and the rotating electric machine having the same according to the present disclosure are not limited to the above examples, and include various modifications. The above embodiments are described in detail for easy understanding of the configurations of the stator and the like according to the present disclosure, and are not necessarily limited to those having all the configurations described. Moreover, it is possible to add, delete, or replace a part of the configuration of the embodiment with another configuration.

10: Rotary electric machine, 11: Rotor, 12: Rotor core, 13: Rotating shaft, 15: Slot, 18: Permanent magnet, 20: Stator, 21: Stator core, 40: Coil, 41: First turn , 42: Second turn, 43: Third turn, 44: Fourth turn, 46: Lead wire, 47: Neutral point, 50: Housing, 60: Stator coil, 130: Liquid cooling jacket, 144, 145: Bearing 150: Refrigerant reservoir 153: Refrigerant passage 154: Refrigerant outlet 155: Refrigerant outlet 401: First insulating coating 402: Second insulating coating 300: Insulating paper 301: Slot liner 501 : fixing varnish, 157: refrigerant.

Claims

A stator that constitutes a rotating electric machine,
a stator core;
a coil;
The coil has a multi-phase winding, a lead wire, and a neutral point to which the multi-phase winding is electrically connected,
The winding includes a conductor, and a first insulating coating and a second insulating coating covering the conductor,
The second insulating coating has higher surge resistance than the first insulating coating,
The stator according to claim 1, wherein the range of the second insulating coating covering the conductor is 20 to 50% of the total length of the winding on the neutral point side.
The stator according to claim 1, wherein said first insulation coating and said second insulation coating contain any one of polyimide, polyamideimide, polyesterimide and polyester.
The stator according to claim 1, wherein said second insulating coating contains inorganic particles.
The stator according to claim 3, wherein said second insulating coating has a higher content of said inorganic particles than said first insulating coating.
The stator according to claim 3, wherein the inorganic particles include any one of silica, alumina and mica.
The stator according to claim 1, wherein said windings are composed of segment coils.
The stator according to claim 6, wherein said segment coil has only one of said first insulating coating and said second insulating coating.
a stator according to any one of claims 1 to 7;
A rotating electric machine, comprising a rotor.