Technical Field
[0001]
5 The present invention relates to a three-phase electric motor.
Background Art
[0002]
Some conventional electric motors include a stator winding constituted by both
of copper and aluminum conductors to reduce its weight and cost. Aluminum,
10 however, has a greater ionization tendency than copper. The ionization tendency is
an indicator used to express the degree of cationization in an aqueous solution. For
this reason, a direct contact between aluminum and copper in a neutral point of Y-
connected three-phase winding causes a connection failure at high possibility
because ions are emitted from aluminum to copper and wires corrode, and
15 consequently, the contact resistance is increased. Such corrosion of the wires is
called dissimilar-metal corrosion, or electrolytic corrosion.
[0003]
To prevent this dissimilar-metal corrosion, techniques relating to a wiring
method at the neutral point have been proposed (e.g., see Patent Literature 1). An
20 electric motor of Patent Literature 1 employs a configuration including an electrolytic-
corrosion prevention part made of a material having greater ionization tendency than
aluminum, which is sacrificed by corroding itself and thus prevents windings made of
an aluminum-containing material from corroding.
Citation List
25 Patent Literature
[0004]
Patent Literature 1: Japanese Unexamined Patent Application Publication No.
2016-25704
Summary of Invention
30 Technical Problem
2

[0005]
An electric motor of Patent Literature 1, however, requires forming a neutral
point connection part constituting the neutral point in Y-connection by welding, and
covering the neutral point connection part thus formed with the electrolytic-corrosion
5 prevention part and thereafter further requires insulation by an insulating part. That
is, the electric motor configured as described in Patent Literature 1 still has problems that providing the electrolytic-corrosion prevention part increases the number of parts, lowers the working efficiency for manufacturing an electric motor due to labor therefor, and increases material costs therefor.
10 [0006]
The present invention has been made to solve the above-mentioned problems and its object is to provide an electric motor that efficiently prevents dissimilar-metal corrosion at neutral points with a small number of parts and reduced costs. Solution to Problem
15 [0007]
An electric motor according to one embodiment of the present invention includes a three-phase winding provided to a stator core, and a neutral-point housing part for housing neutral points of the three-phase winding, wherein each phase of the three-phase winding includes a first winding part made of a copper wire and a second
20 winding part made of an aluminum wire, the neutral-point housing part houses the
neutral point of the first winding part of each of the phases and the neutral point of the second winding part of each of the phases and has at least one contact prevention part having insulating properties and a plurality of housing parts partitioned by the contact prevention part, and the neutral point of the first winding parts and the neutral
25 point of the second winding parts are housed in their respective housing parts.
Advantageous Effects of Invention [0008]
According to one embodiment of the present invention, an insulating part alone can prevent a contact between dissimilar metals since the neutral point of the first
30 winding parts and the neutral point of the second winding parts are housed in their
3

respective housing parts; therefore, a highly reliable three-phase electric motor can
be provided by efficiently preventing dissimilar-metal corrosion at neutral points with a
small number of parts and reduced costs.
Brief Description of Drawings
5 [0009]
[Fig. 1] Fig. 1 schematically illustrates a side of an electric motor according to Embodiment 1 of the present invention.
[Fig. 2] Fig. 2 is a wiring diagram of a Y-connected stator winding included in
the electric motor according to Embodiment 1 of the present invention.
10 [Fig. 3] Fig. 3 is a side view illustrating neutral points and a neutral-point
housing part of the electric motor according to Embodiment 1 of the present invention.
[Fig. 4] Fig. 4 is a wiring diagram of a Y-connected stator winding included in an electric motor according to Embodiment 2 of the present invention.
[Fig. 5] Fig. 5 is a side view illustrating neutral points and a neutral-point
15 housing part of the electric motor according to Embodiment 2 of the present invention.
[Fig. 6] Fig. 6 is a wiring diagram of a Y-connected stator winding included in an electric motor according to Embodiment 3 of the present invention.
[Fig. 7] Fig. 7 is a side view illustrating neutral points and a neutral-point
housing part of the electric motor according to Embodiment 3 of the present invention.
20 Description of Embodiments
[0010] Embodiment 1.
Fig. 1 schematically illustrates a side of an electric motor according to
Embodiment 1 of the present invention. As illustrated in Fig. 1, an electric motor 200
25 is a three-phase electric motor driven by a three-phase AC power supply. The
electric motor 200 includes a body shell 210 forming the outer contour, a stator 220
having an annular shape, a rotor 230 provided in the inner periphery of the stator 220
to rotate, and a shaft 240 coupled to the rotor 230. The stator 220 has a stator core
220a and a three-phase winding 100, which is a Y-connected stator winding (see Fig.
30 2). The three-phase winding 100 is wound onto the stator core 220a.
4

[0011]
Fig. 2 is a wiring diagram of a Y-connected stator winding included in the
electric motor according to Embodiment 1 of the present invention. As illustrated in
Fig. 2, the electric motor 200 adopts a three-winding Y-connection as a winding
5 method for the three-phase winding 100.
[0012]
The three-phase winding 100 is connected to a power supply device or a commercial power supply (not shown) supplying a three-phase AC power supply and has an assembly of three independent windings. Specifically, the three-phase
10 winding 100 includes, as the assembly of the independent windings, a U-phase
winding part 10, a V-phase winding part 20, and a W-phase winding part 30, which are to be connected to U phase, V phase, and W phase of the three-phase AC power supply, respectively. [0013]
15 Each of the U-phase winding part 10, the V-phase winding part 20, and the W-
phase winding part 30 has three windings consisting of two copper wires and one aluminum wire. More specifically, the U-phase winding part 10 includes a U-phase copper winding part 11 and a U-phase copper winding part 12, each of which is made of a copper wire, and a U-phase aluminum winding part 13 made of an aluminum
20 wire. The V-phase winding part 20 includes a V-phase copper winding part 21 and a
V-phase copper winding part 22, each of which is made of a copper wire, and a V-phase aluminum winding part 23 made of an aluminum wire. The W-phase winding part 30 includes a W-phase copper winding part 31 and a W-phase copper winding part 32, each of which is made of a copper wire, and a W-phase aluminum winding
25 part 33 made of an aluminum wire.
[0014]
Each of the U-phase copper winding part 11, the U-phase copper winding part 12, the V-phase copper winding part 21, the V-phase copper winding part 22, the W-phase copper winding part 31, and the W-phase copper winding part 32 corresponds
30 to "the first winding part" of the present invention. Each of the U-phase aluminum
5

winding part 13, the V-phase aluminum winding part 23, and the W-phase aluminum
winding part 33 corresponds to "the second winding part" of the present invention.
That is, in the three-phase winding 100, one ends of the first winding parts of the
respective phases are Y-connected to one another, and one ends of the second
5 winding parts of the respective phases are Y-connected to one another.
[0015]
Here, the copper wires include wires made of a material containing copper, such as a copper alloy. The aluminum wires include wires made of a material containing aluminum, such as an aluminum alloy.
10 [0016]
The U-phase copper winding part 11 has a winding 11 a, and a terminal wire 11b and a terminal wire 11c, which are respectively one terminal and the other terminal of the U-phase copper winding part 11. The U-phase copper winding part 12 has a winding 12a, and a terminal wire 12b and a terminal wire 12c, which are
15 respectively one terminal and the other terminal of the U-phase copper winding part
12. The U-phase aluminum winding part 13 has a winding 13a, and a terminal wire 13b and a terminal wire 13c, which are respectively one terminal and the other terminal of the U-phase aluminum winding part 13. [0017]
20 The V-phase copper winding part 21 has a winding 21a, and a terminal wire
21b and a terminal wire 21c, which are respectively one terminal and the other terminal of the V-phase copper winding part 21. The V-phase copper winding part 22 has a winding 22a, and a terminal wire 22b and a terminal wire 22c, which are respectively one terminal and the other terminal of the V-phase copper winding part
25 22. The V-phase aluminum winding part 23 has a winding 23a, and a terminal wire
23b and a terminal wire 23c, which are respectively one terminal and the other terminal of the V-phase aluminum winding part 23. [0018]
The W-phase copper winding part 31 has a winding 31a, and a terminal wire
30 31b and a terminal wire 31c, which are respectively one terminal and the other
6

terminal of the W-phase copper winding part 31. The W-phase copper winding part
32 has a winding 32a, and a terminal wire 32b and a terminal wire 32c, which are
respectively one terminal and the other terminal of the W-phase copper winding part
32. The W-phase aluminum winding part 33 has a winding 33a, and a terminal wire
5 33b and a terminal wire 33c, which are respectively one terminal and the other
terminal of the W-phase aluminum winding part 33. [0019]
In addition, the three-phase winding 100 includes a copper neutral point 40 and an aluminum neutral point 50. The copper neutral point 40 is a neutral point formed
10 by connecting together a plurality of the first winding parts made of copper wires.
Specifically, the copper neutral point 40 is a neutral point formed by connecting together two sets of the first winding parts, i.e., each pair of the first winding parts of the respective phases. The aluminum neutral point 50 is a neutral point formed by connecting together a plurality of the second winding parts made of aluminum wires.
15 Specifically, the aluminum neutral point 50 is a neutral point formed by connecting
together a set of the second winding parts, i.e., each of the second winding parts of the respective phases. [0020]
The terminal wire 11b, the terminal wire 12b, the terminal wire 21b, the terminal
20 wire 22b, the terminal wire 31b, and the terminal wire 32b are connected to one
another at the copper neutral point 40. The terminal wire 13b, the terminal wire 23b, and the terminal wire 33b are connected to one another at the aluminum neutral point 50. That is, in the three-phase winding 100, the copper neutral point 40 where six copper wires are connected together and the aluminum neutral point 50 where three
25 aluminum wires are connected together are formed. Here, the copper neutral point
40 corresponds to "the neutral point of the first winding parts" of one embodiment of the present invention, and the aluminum neutral point 50 corresponds to "the neutral point of the second winding parts" of one embodiment of the present invention. [0021]
30 In Embodiment 1 of the present invention, the copper neutral point 40 is formed
7

by binding the terminal wire 11b, the terminal wire 12b, the terminal wire 21b, the
terminal wire 22b, the terminal wire 31b, and the terminal wire 32b, of which wire
insulation coatings are removed, and twisting those wires along a circumferential line
before welding. The aluminum neutral point 50 is formed by welding the terminal
5 wire 13b, the terminal wire 23b, and the terminal wire 33b, as with the copper neutral
point 40. [0022]
Note that, various methods can be used to form the copper neutral point 40 and the aluminum neutral point 50, in addition to the method described above.
10 Examples of a method for connecting wires together include soldering, TIG (Tungsten
Inert Gas) welding, brazing welding, and connection by crimp terminal. That is, various materials can be used as the jointing material for each of the copper neutral point 40 and the aluminum neutral point 50. [0023]
15 The U-phase winding part 10 has a U-phase connection terminal 110, which is
connected to the U phase via a lead 300. The terminal wire 11c, the terminal wire 12c, and the terminal wire 13c are connected to one another at the U-phase connection terminal 110. The V-phase winding part 20 has a V-phase connection terminal 120, which is connected to the V phase via a lead 300. The terminal wire
20 21c, the terminal wire 22c, and the terminal wire 23c are connected to one another at
the V-phase connection terminal 120. The W-phase winding part 30 has a W-phase connection terminal 130, which is connected to the W phase via a lead 300. The terminal wire 31c, the terminal wire 32c, and the terminal wire 33c are connected to one another at the W-phase connection terminal 130.
25 [0024]
Moreover, the electric motor 200 includes a neutral-point housing part 60 for housing the neutral points of the three-phase winding 100, i.e., the copper neutral point 40 and the aluminum neutral point 50. In Fig. 2, the neutral-point housing part 60 is shown in the broken line for the sake of convenience.
30 [0025]
8

Fig. 3 is a side view illustrating the neutral points and the neutral-point housing
part of the electric motor according to Embodiment 1 of the present invention. As
illustrated in Fig. 3, the copper neutral point 40 and the aluminum neutral point 50 are
inserted into the neutral-point housing part 60 having insulating properties.
5 [0026]
The neutral-point housing part 60 has a side part 61, which is formed by rolling an insulation paper in a film shape a plurality of times to be a cylinder. The neutral-point housing part 60 has an end 62 closing one end of the cylindrical side part 61 and a contact prevention part 64 having insulation properties, which are welded
10 through, for example, ultrasonic welding. Also, the neutral-point housing part 60 has
an opening port 63 at the other end of the cylindrical side part 61. That is, the neutral-point housing part 60 has a first housing part 70 and a second housing part 80, which are partitioned by the contact prevention part 64. [0027]
15 The copper neutral point 40 and the aluminum neutral point 50 are inserted
from the opening port 63 to be respectively housed in the first housing part 70 and the
second housing part 80.
[0028]
In Embodiment 1 of the present invention, the neutral-point housing part 60 is
20 made of an insulation paper. It is preferable that the insulation paper forming the
neutral-point housing part 60 be prepared by laminating a plurality of insulation papers, each of which has a thickness of about 100 |j,m, to have the whole thickness of 500 |j,m. A material usable for the insulation paper forming the neutral-point housing part 60 is a weldable material, such as NOMEX or PET (polyethylene
25 terephthalate).
[0029]
Incidentally, aluminum has a greater ionization tendency than copper. For this reason, a direct contact between aluminum and copper generates dissimilar-metal corrosion where ions are emitted from aluminum to copper due to a contact between
30 dissimilar metals, and aluminum corrodes. In regard to this matter, since the electric
9

motor 200 of Embodiment 1 of the present invention includes the contact prevention
part 64 functioning as a partition in the neutral-point housing part 60, a contact
between the copper neutral point 40 and the aluminum neutral point 50, i.e., a contact
between the copper wires and the aluminum wires, can be prevented. It is therefore
5 possible to prevent the dissimilar-metal corrosion at the neutral points.
[0030]
That is, the electric motor 200 adopts an improved wiring method for the neutral points of the three-phase winding 100, and the copper neutral point 40 and the aluminum neutral point 50 are respectively housed in the first housing part 70 and
10 the second housing part 80. In this way, the neutral-point housing part 60 alone can
prevent a contact between dissimilar metals; therefore, a highly reliable three-phase electric motor can be provided by efficiently preventing dissimilar-metal corrosion at the neutral points with a small number of parts and reduced costs. [0031]
15 Here, the jointing material for the copper neutral point 40 and the jointing
material for the aluminum neutral point 50 may be the same kind of metal or different kinds of metals. Even if the jointing material for the copper neutral point 40 and the jointing material for the aluminum neutral point 50 are dissimilar metals, and the jointing material for the copper neutral point 40 has an ionization tendency much
20 different from the jointing material for the aluminum neutral point 50, the contact
prevention part 64 is interposed between the copper neutral point 40 and the aluminum neutral point 50 in the neutral-point housing part 60. Accordingly, the jointing material for the copper neutral point 40 and the jointing material for the aluminum neutral point 50 do not come into contact with each other, thereby
25 preventing the dissimilar-metal corrosion.
[0032] Embodiment 2
The overall configuration of an electric motor of Embodiment 2 is the same as that of the electric motor 200 described with reference to Fig. 1, and therefore the
30 same reference numerals as with Embodiment 1 will be used below. The same
10

reference numerals are used for the components equivalent to those in aforementioned Embodiment 1 and any repetitive description thereof will be omitted. [0033]
Fig. 4 is a wiring diagram of a Y-connected stator winding included in the
5 electric motor 200 according to Embodiment 2 of the present invention. The electric
motor 200 according to Embodiment 2 includes a three-phase winding 100A, which is Y-connected and provided to the stator core 220a. As illustrated in Fig. 4, the three-phase winding 100A includes a copper neutral point 40a, a copper neutral point 40b, and the aluminum neutral point 50. Each of the copper neutral point 40a and the
10 copper neutral point 40b is a neutral point formed by connecting together a set of the
first winding parts, i.e., corresponding ones of the first winding parts of the respective phases. [0034]
Specifically, the terminal wire 11b, the terminal wire 21b, and the terminal wire
15 31b are connected to one another at the copper neutral point 40a. The terminal wire
12b, the terminal wire 22b, and the terminal wire 32b are connected to one another at the copper neutral point 40b. That is, in the three-phase winding 100A, the copper neutral point 40a where three copper wires are connected together, the copper neutral point 40b where another three copper wires are connected together, and the
20 aluminum neutral point 50 where three aluminum wires are connected together are
formed. The copper neutral point 40a and the copper neutral point 40b are formed in the same way as the copper neutral point 40 in Embodiment 1. [0035]
Here, each of the copper neutral point 40a and the copper neutral point 40b
25 corresponds to "the neutral point of the first winding parts" of one embodiment of the
present invention, and the aluminum neutral point 50 herein corresponds to "the neutral point of the second winding parts" of one embodiment of the present invention. [0036]
11

As described above, in the three-phase winding 100A, the number of wires
connected to each neutral point for the copper wires is reduced to three compared to
six wires in the three-phase winding 100 of Embodiment 1; therefore, it becomes less
difficult to connect the wires, so that a connection failure can be more reliably
5 prevented.
[0037]
Moreover, the electric motor 200 of Embodiment 2 of the present invention includes a neutral-point housing part 60A for housing the neutral points of the three-phase winding 100A, i.e., the copper neutral point 40a, the copper neutral point 40b,
10 and the aluminum neutral point 50. In Fig. 4, the neutral-point housing part 60A is
shown in the broken line for the sake of convenience. [0038]
Fig. 5 is a side view illustrating the neutral points and the neutral-point housing part of the electric motor according to Embodiment 2 of the present invention. The
15 neutral-point housing part 60A has the side part 61, which is formed by rolling an
insulation paper in a film shape a plurality of times to be a cylinder. The neutral-point housing part 60A has the end 62 closing one end of the cylindrical side part 61, and a contact prevention part 64a and a contact prevention part 64b having insulation properties, and the end 62 and each of the contact prevention parts 64a and 64b are
20 welded through, for example, ultrasonic welding. Also, the neutral-point housing part
60A has the opening port 63 at the other end of the cylindrical side part 61. That is the neutral-point housing part 60A has a first housing part 70a, a second housing part 80, and a third housing part 70b, which are partitioned by the contact prevention parts 64a and 64b.
25 [0039]
The copper neutral point 40a, the copper neutral point 40b, and the aluminum neutral point 50 are inserted from the opening port 63 to be respectively housed in the first housing part 70a, the third housing part 70b, and the second housing part 80. [0040]
12

As described above, the number of housing parts included in the neutral-point
housing part 60A equals to the sum of the number of neutral points of the first winding
parts and the number of neutral points of the second winding part. Further, in the
electric motor 200 of Embodiment 2, the copper neutral point 40a, the copper neutral
5 point 40b, and the aluminum neutral point 50 are respectively housed in the first
housing part 70a, the third housing part 70b, and the second housing part 80. In this way, the neutral-point housing part 60A alone as an insulation material can prevent a contact between dissimilar metals; therefore, a highly reliable three-phase electric motor can be provided by efficiently preventing dissimilar-metal corrosion at the
10 neutral points with a small number of parts and reduced costs.
[0041]
That is, in the neutral-point housing part 60A, the contact prevention part 64b functions as a partition between the neutral points of the copper winding parts, i.e., the copper neutral point 40a and the copper neutral point 40b, and the neutral point of
15 the aluminum winding part, i.e., the aluminum neutral point 50. Accordingly, it is
possible to prevent dissimilar-metal corrosion at the neutral points since a contact between the copper wires and the aluminum wire can be prevented. [0042]
In addition, since the neutral-point housing part 60A has the contact prevention
20 part 64a interposed between the copper neutral point 40a and the copper neutral
point 40b, a contact between the copper neutral point 40a and the aluminum neutral point 50 can be more reliably prevented. Even when the jointing material for the copper neutral point 40a and the jointing material for the copper neutral point 40b are dissimilar metals, and the jointing material for the copper neutral points 40 has an
25 ionization tendency much different from the jointing material for the aluminum neutral
point 50, the dissimilar-metal corrosion can be effectively prevented. [0043]
Since, in the three-phase winding 100A, the number of copper wires connected to each neutral point for the copper wires is reduced compared to that in the three-
30 phase winding 100, it is possible to more satisfactorily connect the copper wires, so
13

that a connection failure can be more reliably prevented. Other effects that the
electric motor 200 of Embodiment 2 has are the same as that described in
Embodiment 1.
[0044]
5 Embodiment 3.
The overall configuration of an electric motor of Embodiment 3 is the same as that of the electric motor 200 of Embodiment 1 described with reference to Fig. 1, and therefore the same reference numerals as with Embodiment 1 will be used below. The same reference numerals are used for the components equivalent to those in
10 Embodiments 1 and 2 and any repetitive description thereof will be omitted.
[0045]
Fig. 6 is a wiring diagram of a Y-connected stator winding included in the electric motor according to Embodiment 3 of the present invention. An electric motor 200 according to Embodiment 3 includes a three-phase winding 100B, which is Y-
15 connected and provided to the stator core 220a. Also, the electric motor 200
includes a neutral-point housing part 60B for housing neutral points of the three-phase winding 100B, instead of the neutral-point housing part 60A of Embodiment 2. That is, the neutral-point housing part 60B houses the copper neutral point 40a, the copper neutral point 40b, and the aluminum neutral point 50. The configurations of
20 the three-phase winding 100B other than those described above are the same as
those of the three-phase winding 100A of Embodiment 2. [0046]
Fig. 7 is a side view illustrating the neutral points and the neutral-point housing part of the electric motor according to Embodiment 3 of the present invention. The
25 neutral-point housing part 60B has the side part 61, which is formed by rolling an
insulation paper in a film shape a plurality of times to be a cylinder. The neutral-point housing part 60B has the end 62 closing one end of the cylindrical side part 61 and a contact prevention part 64c having insulation properties, which are welded through, for example, ultrasonic welding. Also, the neutral-point housing part 60B has the
30 opening port 63 at the other end of the cylindrical side part 61. That is, the neutral-
14

point housing part 60B has a first housing part 70c and the second housing part 80,
which are partitioned by the contact prevention part 64c.
[0047]
The copper neutral point 40a, the copper neutral point 40b, and the aluminum
5 neutral point 50 are inserted from the opening port 63, and the copper neutral point
40a and the copper neutral point 40b are housed in the first housing part 70c, and the aluminum neutral point 50 is housed in the second housing part 80. That is, two neutral points out of the neutral points of the first winding parts and the neutral point of the second winding part are housed in one housing part.
10 [0048]
As described above, the number of housing parts included in the neutral-point housing part 60B is less than the sum of the number of neutral points of the first winding parts and the number of neutral points of the second winding part. Further, in the electric motor 200 of Embodiment 3, the copper neutral point 40a and the
15 copper neutral point 40b are housed in the first housing part 70a, and the aluminum
neutral point 50 is housed in the second housing part 80. In this way, the neutral-point housing part 60B alone can prevent contact between dissimilar metals; therefore, a highly reliable three-phase electric motor can be provided by efficiently preventing dissimilar-metal corrosion at the neutral points with a small number of
20 parts and reduced costs.
[0049]
Moreover, the neutral-point housing part 60B of Embodiment 3 has one contact prevention part, whereas the aforementioned neutral-point housing part 60A of Embodiment 2 has two contact prevention parts. As a result, the productivity can be
25 improved, since the neutral-point housing part 60B requires fewer welding points than
the neutral-point housing part 60A and consequently requires less man-hours. In addition, it is not required to house the copper neutral point 40a and the copper neutral point 40b in different housing parts, which makes it easier to house the copper neutral point 40a and the copper neutral point 40b; as a result, working efficiency can
15

be improved. Other effects that the electric motor 200 of Embodiment 3 has are the
same as those described in Embodiment 1 and 2.
[0050]
Here, each of the above-described embodiments is a preferred example of an
5 electric motor, and the technical scope of the present invention is not limited to these
embodiments. For example, although the electric motor 200 described in Embodiments 1 to 3 includes a stator winding with three windings, it is not limited thereto. That is, although each of the U-phase winding part 10, the V-phase winding part 20, and the W-phase winding part 30 has three windings consisting of two copper
10 wires and one aluminum wire in Embodiments 1 to 3, the three windings may consist
of one copper wire and two aluminum wires. In this case, the three-phase winding 100, 100A, or 100B may include a neutral point formed by connecting together two sets of the second winding parts or two neutral points, each of which is formed by connecting together a set of the second winding parts.
15 [0051]
Further, each of the U-phase winding part 10, the V-phase winding part 20, and the W-phase winding part 30 may include two or four and more windings instead of three windings, as long as the windings consist of copper wires and aluminum wires. When the winding part of each phase includes four and more windings, the ratio of
20 the number of the copper winding parts to the number of the aluminum winding parts
in the winding part of each phase can be optionally changed. Furthermore, the number of neutral points of the first winding parts and the second winding parts can be optionally changed. In addition, the number of neutral points housed in each housing part may be not limited to one or two and be three or more. That is, the
25 neutral-point housing part may be configured differently as long as it has at least one
contact prevention part having insulating properties and a plurality of housing parts partitioned by the contact prevention part. [0052]
Specifically, in the electric motors 200 described in Embodiment 1 to 3, the
30 neutral points of the first winding parts and the neutral points of the second winding
16

parts are required to be housed in different housing parts. Further, in the electric
motors 200 in Embodiments 2 and 3, each phase of the three-phase windings 100A
and 100B is required to have one or a plurality of the first winding parts and one or a
plurality of the second winding parts. In addition, it is required to multiply provide at
5 least one of the neutral points of the first winding parts and the neutral points of the
second winding parts. [0053]
In the electric motor 200 of Embodiment 2, at least two out of the neutral points of the first winding parts and the second winding parts are required to be housed in
10 the same one housing part. Here, the number of housing parts may be greater than
the sum of the number of neutral points of the first winding parts and the number of neutral points of the second winding parts; however, the labor and costs will be increased by providing the housing part that does not house any neutral points. Accordingly, the number of housing parts included in the neutral-point housing part
15 preferably equals to the sum of the number of neutral points of the first winding parts
and the number of neutral points of the second winding parts. [0054]
In the electric motor 200 of Embodiment 3, at least two out of the neutral points of the first winding parts and the second winding parts are required to be housed in
20 the same one housing part. Here, for example, the neutral-point housing part 60A of
Embodiment 2 may be applied to the electric motor 200 of Embodiment 3, and neutral-point housing part having more housing parts may be used with one of the housing parts being empty; however, the labor and costs will be increased by providing the housing part that does not house any neutral points. Accordingly, the
25 number of housing parts included in the neutral-point housing part is preferably less
than the sum of the number of neutral points of the first winding parts and the number of neutral points of the second winding parts to provide the housing parts required. [0055]
In other words, each of the U-phase winding part 10, the V-phase winding part
30 20, and the W-phase winding part 30 is required to include at least one copper
17

winding part and at least one aluminum winding part. It is preferable that one or a
plurality of the copper neutral points and one or a plurality of the aluminum neutral
points be housed in different housing parts. When the electric motor 200 includes a
plurality of at least one of the copper neutral points and the aluminum neutral points,
5 the number of housing parts and the number of neutral points may be the same, and
the plurality of neutral points may be housed in their respective housing parts. Alternatively, the number of housing parts may be less than the number of neutral points, and at least two of the plurality of the neutral points may be housed in one housing part.
10 [0056]
In addition, Figs 3, 5, and 7 schematically illustrate each component, and its features such as size and shape are not limited to the illustrations in the respective figures. For example, a position at which the contact prevention part 64 is welded in Fig. 2, is not limited to a center part of the end 62 in a side view and can be optionally
15 changed depending on, for example, sizes of the copper neutral point 40 and the
aluminum neutral point 50. That is, each housing part included in the neutral-point housing parts 60, 60A, and 60B may be different in size and shape. Reference Signs List [0057]
20 10 U-phase winding part 11, 12 U-phase copper winding part 11a, 12a, 13a,
21a, 22a, 23a, 31a, 32a, 33a winding 11b, 11c, 12b, 12c, 13b, 13c, 21b, 21c,
22b, 22c, 23b, 23c, 31b, 31c, 32b, 32c, 33b, 33c terminal 13 U-phase
aluminum winding part 20 V-phase winding part 21, 22 V-phase copper
winding part 23 V-phase aluminum winding part 30 W-phase winding part
25 31,32 W-phase copper winding part 33 W-phase aluminum winding part
40, 40a, 40b copper neutral point 50 aluminum neutral point 60, 60A,
60B neutral-point housing part 61 side part 62 end 63 opening port
64, 64a, 64b, 64c contact prevention part 70, 70a, 70c first housing part 70b third housing part 80 second housing part 100 100A, 100B three-
30 phase winding 110 U-phase connection terminal 120 V-phase connection
18

terminal 130 W-phase connection terminal 200 electric motor 210
body shell 220 stator 220a stator core 230 rotor 240 shaft 300 lead.
19

WE CLAIM:
[Claim 1]
An electric motor comprising:
a three-phase winding provided to a stator core; and
5 a neutral-point housing part for housing a neutral point of the three-phase
winding,
each phase of the three-phase winding including
a first winding part made of a copper wire; and
a second winding part made of an aluminum wire, and
10 the neutral-point housing part hosing
a neutral point of the first winding part of each phase and a neutral point of the second winding part of each phase and includes
at least one contact prevention part having insulating properties, and
a plurality of housing parts partitioned by the at least one contact
15 prevention part,
the neutral point of the first winding part and the neutral point of the second winding part being housed in their respective ones of the plurality of housing parts.
[Claim 2]
20 The electric motor of claim 1,
wherein the three-phase winding includes
at least one set of the first winding part of each phase and at least one set of
the second winding part of each phase, and
at least one of
25 the neutral point of the at least one set of the first winding part of each
phase and
the neutral point of the at least one set of the second winding part of each phase includes a plurality of neutral points
each neutral point of the at least one set of the first winding part of each phase
30 and each neutral point of the at least one set of the second winding part of each
20

phase being housed in a corresponding one of the plurality of housing parts.
[Claim 3]
The electric motor of claim 2, wherein a number of the housing parts equals to
5 a sum of number of neutral points of the at least one set of the first winding part of
each phase and a number of neutral points of the at least one set of the second winding part of each phase.
[Claim 4]
10 The electric motor of claim 1,
wherein the three-phase winding includes
at least one set of the first winding part of each phase and at least one set of the second winding part of each phase, and
at least one of the neutral point of the at least one set of the first winding part of
15 each phase and the neutral point of the at least one set of the second winding part of
each phase includes a plurality of neutral points,
wherein at least two of each neutral point of each set of the first winding
part of each phase being housed in same one of the plurality of housing parts,.
and/or at least two of each neutral point of each set of the second winding part of
20 each phase being housed in same one of the plurality of housing parts.
[Claim 5]
The electric motor of claim 4, wherein the number of housing parts is less than
a sum of the number of neutral points of the at least one set of the first winding part of
25 each phase and the number of neutral points of the at least one set of the second
winding part of each phase.
21