JP7460571B2 - Stator and rotating electric machine having the same - Google Patents

Description

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

In recent years, with the advancement of electrification in automobiles, there is a demand for higher power density in electrical equipment, particularly rotating electrical machines. One method of increasing power density is to increase voltage, which is being promoted by each automobile manufacturer. In response to this, various stators with excellent insulation reliability that can handle high voltages are being considered for rotating electrical machines.

For example, Patent Document 1 discloses a technology that achieves both miniaturization of a rotating electrical machine and high voltage and high output by configuring the slot portion and the coil end portion to have different thicknesses or different insulating materials. ing.

Patent document 2 discloses a technology that increases the insulation resistance by thickening the insulating coating at a specific portion of the conductor, thereby ensuring the insulation performance between the joint and the adjacent segment conductor when joining segment conductors.

In addition, as inverter speeds increase, the rise speed of the input voltage to the motor is also becoming faster. This faster rise speed of the input voltage creates a potential difference even within the same coil, creating new insulation challenges.

Non-Patent Document 1 describes the principle of surge generation in an inverter-driven motor, the entry of surge into the motor, the inter-turn voltage, and the like. Non-Patent Document 1 states that when a surge enters the motor coil, most of the surge voltage is applied to the first turn of the coil, that the voltage rise time may be less than 50 ns, and that the voltage pulse at the first turn and the It is described that a voltage between adjacent turns is generated due to a difference with a delayed voltage pulse after passing.

JP2008-236924A International Application No. 2019/107515

IEEJ Journal, Vol. 126, No. 7, pp. 419-422 (2006)

In the techniques described in Patent Documents 1 and 2, the insulation properties are improved by changing the thickness of the insulation coating. However, it has not been clarified the range in which the insulation of the coil needs to be improved, that is, which part of the windings forming the coil needs to have the insulation improved.

In addition, as described in Non-Patent Document 1, it is generally known that voltages occur between adjacent turns, but the specific range within the coil where insulation measures are required due to the influence of the voltage between adjacent turns has not been clarified.

Therefore, in conventional examples, insulation measures would have been implemented to an unnecessary extent.

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

The present invention relates to a stator constituting a rotating electrical machine, which includes a stator core and a coil, and the coil is electrically connected to a plurality of phase windings, a lead wire, and a plurality of phase windings. the winding includes a conductor, a first insulating coating and a second insulating coating covering the conductor, the second insulating coating being more insulating than the first insulating coating; The second insulating film also has high surge resistance, and the range where the second insulating film covers 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 insulation breakdown in a specific range where the potential difference in the windings that make up the stator coil becomes large.

FIG. 1 is a cross-sectional view showing a rotating electric machine according to an embodiment. 1 is a perspective view showing a stator of a rotating electric machine according to an embodiment; FIG. 2 is a schematic configuration diagram showing a coil having a star connection. FIG. 2 is a schematic diagram showing a coil having four reciprocating windings.

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

After extensive research, including measurements of the stator's voltage distribution rate, the inventors discovered that, due to potential propagation delay, the potential of the windings that make up the stator coil is significantly different from the potential of the lead wires in a specific range from the neutral point.

From these results, we came to the idea that it would be effective to increase the surge resistance of the insulating coating applied to this range.

Specifically, it was found that, of the first and second insulating coatings that cover the conductors that make up the winding, it is desirable to make the surge resistance of the second insulating coating higher than that of the first insulating coating, and to set the range in which the second insulating coating covers the conductor to 20-50% of the entire length of the winding on the neutral point side.

Hereinafter, the insulating coating used for the windings forming the stator of the present disclosure will be described in detail.

(Configuration of the insulating coating)
The insulating coating includes a resin having electrical insulation properties in both the first insulating coating and the second insulating coating. Specific examples of the resin include polyvinyl formal, polyester, polyesterimide, polyamideimide, polyimide, nylon, polyoxymethylene, polyphenylene sulfide, polyetheretherketone, polytetrafluoroethylene, and the like. Among these, polyester, polyesterimide, polyamideimide, and polyimide are preferred from the viewpoints of heat resistance, processability, and adhesiveness. The resin may be used alone or in a multi-layered form of multiple resins. The multi-layering means may be an existing method such as baking coating or multi-layer extrusion, and is not particularly limited. It is preferable that these resins are the same within one segment coil before welding. In other words, it is preferable that the segment coil has only one of the first insulating coating and the second insulating coating.

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

The inorganic particles need only have electrical insulation properties, and include silica, alumina, mica, and the like. These may be used alone or in combination of two or more.

An example of adding inorganic particles is a method of using polyamideimide for the first insulating coating and polyamideimide with nanosilica particles added for the second insulating coating.

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

An example of lowering the dielectric constant is a method of using polyamideimide 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 film is lower than the dielectric constant of the first insulating film.

(Application area of second insulating coating)
The area to which the second insulating coating is applied is between the lead wire, which is the input part of the power supply, and the lead wire and the neutral point, and is adjacent to the neutral point of the surrounding winding part that constitutes the surrounding winding. It is preferable that it is a portion of 20 to 50% of the total length of the circumferential winding portion. This region is a region where the potential difference becomes large due to the rise of the pulse when power is input. Further, when forming an insulating film by baking coating, the resin thickness that improves the surge resistance of the second insulating film is preferably 5% or more and less than 100% of the total, and 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 adhesive strength between the conductor and the coating may be weakened. Furthermore, the thickness of both the first insulating film and the second insulating film is not particularly limited, as long as the thickness is selected to be suitable for the power supply voltage.

(Configuration of Rotating Electric Machine)
Next, the configuration of the rotating electric machine will be described. The embodiments described below are merely examples, and the present invention is not limited to these examples. In the following description, an electric motor used in a hybrid vehicle will be used as an example of a rotating electric machine. In the following description, "axial direction" refers to a direction along the rotation axis of the rotating electric machine. Furthermore, "circumferential direction" refers to a direction along the rotation direction of the rotating electric machine. "Radial direction" refers to a radial direction (radial direction) when the rotation axis of the rotating electric machine is the center. "Inner circumference side" refers to the radial inside (inner diameter side), and "outer circumference side" refers to the opposite direction, i.e., the radial outside (outer diameter side).

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

In this figure, the rotating 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 a permanent magnet 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 circumference of the housing 50. The rotor 11 is rotatably installed on the inner circumference of the stator 20. The housing 50 constitutes the outer casing of the rotating electric machine 10 and is formed into a cylindrical shape by cutting an iron-based material such as carbon steel, by casting steel or an aluminum alloy, or by pressing. The housing 50 is also called a frame or a frame.

A liquid cooling jacket 130 is installed on the outer periphery of the housing 50. The gap between the inner periphery of the liquid cooling jacket 130 and the outer periphery of the housing 50 is a refrigerant passage 153 for a liquid refrigerant 157 such as oil. The refrigerant passage 153 is configured to prevent liquid leakage. The liquid cooling jacket 130 has bearings 144 and 145, and can also be called a "bearing bracket."

In the case of direct liquid cooling, the refrigerant 157 passes through the refrigerant passage 153 and flows out from the refrigerant outlets 154 and 155 toward the stator 20, cooling the stator 20. The refrigerant 157 is then temporarily stored in the refrigerant storage section 150 and circulated by an externally installed pump.

The stator core 21 is made up of laminated thin silicon steel plates.

Heat generated in the coil 40 installed in the stator 20 is transmitted to the housing 50 via the stator core 21, and is transferred to the outside by the refrigerant 157 flowing in the liquid cooling jacket 130, where the heat is 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. Thereby, the rotor 11 rotates at a predetermined position within the stator 20 and at a position facing the stator 20.

To assemble the rotating electric machine 10, the stator 20 is inserted inside the housing 50 and attached to the inner circumferential 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 into the rotating shaft 13.

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

Figure 2 is a perspective view showing an example of a stator of a rotating electric machine according to an 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 on the inner circumference of the stator core 21.

The stator 20 includes a stator core 21 and a stator coil 60 wound around a plurality of slots 15 provided on the inner circumference 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 example, the conductor is made of a copper alloy. By making the cross-sectional shape of the conductor of the stator coil 60 substantially rectangular, the space factor of the conductor in the slot 15 can be improved, and the efficiency of the rotating electric machine 10 can be improved.

Further, a slot liner 301 is provided in each slot 15, and an insulating paper 300 is provided on the outer periphery of the stator core 21 to ensure electrical insulation and adhesion between the stator core 21 and the stator coil 60, etc. There is. The slot liner 301 is formed into a mouth shape, a B shape, or an S shape so as to wrap the copper wire.

The segment-shaped coil is inserted into the slot 15 in which the slot liner 301 is arranged, and then welded to form the stator coil 60. The coil is then fixed by impregnating the slot 15 with adhesive varnish and heating it. In other words, the winding of the stator coil 60 is composed of segment coils.

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

The above explanation is about a permanent magnet type rotating electric machine, but since the feature of the rotating electric machine according to the present disclosure is related to the coil insulation of the stator, the rotor may be an induction type as well as a permanent magnet type. It is also applicable to synchronous reluctance, claw magnetic pole type, etc. Further, although the winding method is a wave winding method, any winding method having similar characteristics can be applied. Further, although the explanation is given for the adductor type, it is equally applicable to the abductor type.

Figure 3 is a schematic 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. Further, the lead lines 26a, 26b, 26c and the neutral point 27 are actually arranged close to each other.

In this figure, if the total length of the line segment connecting the output wire 26a representing the U-phase winding and the neutral point 27 is taken as 100, the winding within a range of length 25 from the neutral point 27, as shown by the thick solid line, is covered with the second insulating coating 402. In other words, 25% of the entire winding from the neutral point 27 is covered with the second insulating coating 402. Meanwhile, the remaining part of the winding shown by the dashed line (75% from the output wire 26a) is covered with the first insulating coating 401. The same is true for the V-phase and W-phase. The output wires 26a, 26b, 26c and the neutral point 27 are also covered with the second insulating coating 402.

Note that although this figure shows the case of star connection, the winding configuration of the present disclosure is not limited to this, and can also be applied to stators with 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 shown 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 winding.

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 reciprocating winding.

Generally, when a pulse voltage is applied to the lead wire 46, a steep change in current value occurs. At this time, induced electromotive force is generated in the winding of the coil 40 due to inductance. Therefore, the pulse voltage is difficult to propagate to the portion of the winding on the neutral point 47 side that is 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 rate of change of current over time becomes particularly significant, and the induced electromotive force also tends to increase.

As a result of intensive experimental studies on applying pulse voltages on the order of MHz to the coil, the inventor of the present invention found that it is possible to cover 20 to 50% of the entire winding from the neutral point with a second insulating film. I came to the conclusion that it is desirable. In other words, it is desirable that the range covered by the second insulating coating in the circumferential winding is 20 to 50% of the total length of the circumferential winding on the neutral point side.

The lower limit of the area covered by the second insulating coating is based on the results of the dielectric breakdown life test in the examples and comparative examples described below. On the other hand, as for the upper limit of this range, it goes without saying that a sufficient life can be obtained by widening the area covered by the second insulating coating, but if the area covered by the second insulating coating is wider than necessary because dense inorganic fine particles are added to the resin, this not only increases the cost but also goes against the weight reduction of the coil. Therefore, the upper limit of this range is preferably 50%. More preferably, it is 40%, and especially preferably 30%. As described below, even with 25%, the same dielectric breakdown life was obtained as when 100% was covered.

Figure 4 shows a coil with four round turns of winding, but in the case of eight round turns of winding, it has been found that it is desirable for the area of the circumferential winding to be covered with the second insulating coating to be 20 to 50% of the total length of the circumferential winding on the neutral point side. In other words, if the coil has eight round turns of winding, it is sufficient to cover approximately two round turns of the winding on the neutral point side with the second insulating coating.

Examples and comparative examples will be described below.

In the stator of the example, etc., the end of the lead wire and the neutral point, and the winding (circular winding) that constitutes the coil located between the lead wire and the neutral point, on the neutral point side. A predetermined portion is covered with the second insulating film, and the other windings are covered with the first insulating film. The second insulating coating has better surge resistance than the first insulating coating. Note that the thicknesses (film thicknesses) of the first insulating film and the second insulating film are the same, which is 70 μm.

The first insulating coating was made of polyamideimide that does not contain inorganic fine particles.

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

The first insulating coating was made of polyamideimide containing nano-silica particles, with 20% of the total thickness being made up of the material.

On the other hand, as the second insulating film, polyamideimide containing nanosilica particles in 60% of the total film thickness was used. The range covered by the second insulating coating in the circumferential winding was 25% of the total length of the circumferential winding on the neutral point side.

(Comparative example 1)
Polyamideimide containing no nanosilica particles was used as the insulating coating in all areas of the winding. That is, the entire area was covered with the first insulating film without using the second insulating film.

(Comparative Example 2)
The first insulating coating was made of polyamideimide containing no inorganic fine particles.

On the other hand, the second insulating coating was made of polyamideimide containing nano-silica particles for 60% of the total thickness. The area of the circumferential winding covered by the second insulating coating was 15% of the total length of the circumferential winding on the neutral point side.

(Reference example)
The insulating coating was made of polyamideimide containing nano-silica particles for 60% of the total thickness over the entire area of the peripheral winding, i.e., the entire area was covered with the second insulating coating without using the first insulating coating.

In addition, since these stators use segment coils, the application areas of the first insulating coating and the application areas of the second insulating coating can be appropriately selected from either the segment coil having the first insulating coating or the segment coil having the second insulating coating when inserting the core, and therefore they can be manufactured using conventional manufacturing equipment.

(Verification of effectiveness)
A line-to-line voltage life test was carried out on the fabricated 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 Electronics Technology Co., Ltd. was used as a power source, 2 kV at 500 Hz was applied to the U-phase output wire, and the V-phase was grounded. The neutral point was previously disconnected.

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 1.5 times longer to undergo dielectric breakdown than Comparative Example 1, which was made using only a coil that does not have the second insulating coating with excellent surge resistance, and that the life span is improved in terms of insulation.

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

Furthermore, although the stators of Examples 1 and 2 use coils with a first insulating coating that has poor surge resistance in some parts, they have a dielectric breakdown life equivalent to that of the reference example, which was made with a coil having only the second insulating coating that has excellent surge resistance.

In addition, several experiments have shown 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 a result, the stator disclosed herein and the rotating electric machine having the stator can achieve both a reduction in the amount of expensive, surge-resistant insulating coating used and improved insulation properties.

The stator and rotating electric machine having the same according to the present disclosure are not limited to the above-mentioned embodiment, but include various modified examples. The above-mentioned embodiment is described in detail to clearly explain the configuration of the stator and the like according to the present disclosure, and is not necessarily limited to having all of the configurations described. In addition, it is possible to add, delete, or replace part of the configuration of the embodiment with other configurations.

10: rotating 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: outlet 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: adhesive varnish, 157: refrigerant.

Claims (8)

A stator that constitutes a rotating electric machine,
stator core;
comprising a coil;
The coil has multiple phase windings, a lead wire, and a neutral point to which the multiple phase windings are electrically connected,
The winding includes a conductor, a first insulation coating and a second insulation coating covering the conductor,
The second insulating coating has higher surge resistance than the first insulating coating,
In the stator, the range in which the second insulating film covers 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 the first insulating coating and the second insulating coating include any one of polyimide, polyamide-imide, polyester-imide, and polyester. The stator of claim 1, wherein the second insulating coating contains inorganic particles. The stator according to claim 3, wherein the second insulating coating has a higher content of inorganic particles than the 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 the winding is comprised of segment coils. The stator according to claim 6, wherein the segment coil has only one of the first insulating coating and the second insulating coating. A stator according to any one of claims 1 to 7;
A rotating electric machine comprising:

Images