U.S. patent application number 09/731862 was filed with the patent office on 2001-09-13 for motor/generator.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. Invention is credited to Arimitsu, Minoru, Nakano, Masaki.
Application Number | 20010020805 09/731862 |
Document ID | / |
Family ID | 26579449 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010020805 |
Kind Code |
A1 |
Nakano, Masaki ; et
al. |
September 13, 2001 |
Motor/generator
Abstract
A first motor/generator unit (10A, 11) comprises a first rotor
(42, 42B, 42C) and a first stator (40, 40A, 40B, 40C) provided with
a plurality of coils. A second motor/generator unit (10B, 11)
comprises a second rotor (43, 43B, 43C) and a second stator (41,
41A, 41B, 41C) provided with a plurality of coils. Providing that
the number of coils in the first stator (40, 40A, 40B, 40C) is S1,
the number of pairs of magnetic poles in the magnet of the first
rotor (42, 42B, 42C) is P1, and the number of phases in a first
alternating current which drives the first rotor (42, 42B, 42C)
through the coils of the first stator (40, 40A, 40B, 40C) is M1,
the coils of the first stator (40, 40A, 40B, 40C) are divided into
K1 groups satisfying the equation K1=S1/M. The coils in each group
are mutually connected by either a Y connection or a delta
connection. Providing that the number of coils in the second stator
(41, 41A, 41B, 41C) is S2, the number of pairs of magnetic poles in
the magnet of the second rotor (43, 43B, 43C) is P1, and the number
of phases in the second alternating current which drives the second
rotor (43, 43B, 43C) through the coils of the second stator (41,
41A, 41B, 41C) is M2, the coils of the second stator (41, 41A, 41B,
41C) are divided into K2 groups satisfying the equation K2=S2/M2,
The coils in each group are mutually connected by either a Y
connection or a delta connection. A coil with a coil number j in a
group number i of the first stator (40, 40A, 40B, 40C) is mutually
connected with a coil with a coil number i in a group number j of
the second stator (41, 41A, 41B, 41C), it is possible to suppress
an ineffectual current generated when two motor/generator units
(10A, 10B, 11) are independently driven by the same inverter (32,
32B).
Inventors: |
Nakano, Masaki; (Yokohama
city, JP) ; Arimitsu, Minoru; (Yokosuka city,
JP) |
Correspondence
Address: |
RICHARD L. SCHWAAB,
FOLEY & LARDNER, Washington Harbour
3000 K Street, N.W., Suite 500,
P.O. Box 25696
Washington
DC
20007-8696
US
|
Assignee: |
NISSAN MOTOR CO., LTD.
|
Family ID: |
26579449 |
Appl. No.: |
09/731862 |
Filed: |
December 8, 2000 |
Current U.S.
Class: |
310/112 ;
310/184 |
Current CPC
Class: |
H02K 11/048 20130101;
H02P 5/00 20130101; H02K 16/00 20130101; H02P 5/74 20130101 |
Class at
Publication: |
310/112 ;
310/184 |
International
Class: |
H02K 007/20; H02K
019/26 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 1999 |
JP |
11-351613 |
Nov 27, 2000 |
JP |
2000-358004 |
Claims
What is claimed is:
1. A motor/generator comprising a first motor/generator unit
comprising a first rotor provided with a magnet and a first stator
provided with a plurality of coils facing the first rotor, and a
second motor/generator unit comprising a second rotor provided with
a magnet and a second stator provided with a plurality of coils
facing the second rotor, wherein: providing that the number of
coils in the first stator is S1, the number of pairs of magnetic
poles in the magnet of the first rotor is P1, and the number of
phases in a first alternating current which drives the first rotor
through the coils of the first stator is M1, the coils of the first
stator are divided into groups of the number of K1 satisfying the
equation K1=S1/M1, the coils in each group of the first stator
being mutually connected by any of a Y connection and a delta
connection; providing that the number of coils in the second stator
is S2, the number of pairs of magnetic poles in the magnet of the
second rotor is P2, and the number of phases in a second
alternating current which drives the second rotor through the coils
of the second stator is M2, the coils of the second stator are
divided into groups of the number of K2 satisfying the equation
K2=S2/M2, the coils in each group of the second stator being
mutually connected by any of a Y connection and a delta connection;
and providing that the groups of the first stator is numbered from
1 to K1/A, A being a natural number, the coils in each group of the
first stator is numbered from 1 to M1, the groups of the second
stator is numbered from 1 to K2/B, B being a natural number, the
coils in each group of the second stator is numbered from 1 to M2,
and i and j are natural numbers, a coil with a coil number j in a
group number i of the first stator and a coil of a coil number i in
a group number j of the second stator are connected to each
other.
2. The motor/generator as defined in claim 1, wherein a coil with a
coil number j in a group number i of the first stator and a coil
with a coil number i in a group number j of the second stator are
connected in series with an output terminal of an inverter, the
inverter having output terminals of the number of 1 K1 A K2 B which
output a composite current comprising a first alternating current
and a second alternating current with a fixed phase difference.
3. The motor/generator as defined in claim 2, wherein the inverter
outputs the composite current comprising a first alternating
current having a phase difference of 2 360 j - 1 M1 degrees with
respect to a coil with a coil number 1 in a group number i of the
first stator and a second alternating current having a phase
difference 3 360 i - 1 M2 degrees with respect to a coil with a
coil number 1 in a group number j of the second stator, to an
output terminal of the inverter to which a coil with a coil number
j in a group number i of the first stator and a coil with a coil
number i in a group number j of the second stator are
connected.
4. The motor/generator as defined in claim 1, wherein the coils in
each group of the first stator are mutually connected by a Y
connection and the coils in each group of the second stator are
mutually connected by a Y connection.
5. The motor/generator as defined in claim 3, wherein a neutral
point resulting from a Y connection of a coils in each group of the
first stator and a neutral point resulting from a Y connection of a
coils in each group of the second stator are respectively earthed
through an impedance component.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the driving efficiency of two
motor/generators driven independently by single inverter.
BACKGROUND OF THE INVENTION
[0002] Tokkai Hei 11-275826 published by the Japanese Patent Office
in 1999 discloses a motor/generator which drives a plurality of
rotors independently by applying a composite polyphase alternating
current to a set of stator coils. The invention disclosed in Tokkai
Hei 11-275826 is also disclosed in U.S. patent application Ser. No.
09/275,785 filed on Mar. 25, 1999 before the priority date of this
invention and was granted as U.S. Pat. No. 6,049,152 after the
priority date of this invention.
[0003] In the motor/generator disclosed in Tokkai Hei 11-275826,
the composite polyphase alternating current with a fixed angular
phase difference is supplied from an inverter to coils of each
phase in the stator.
SUMMARY OF THE INVENTION
[0004] The research carried out by the present inventors has
demonstrated that it is possible to drive two motors independently,
if the rotors have a different number of magnetic poles, by
connecting coils of the two stators to an inverter in parallel.
[0005] However with the above arrangement, the current for driving
the rotation of one motor also flows in the coils of the other
motor. When the number of magnetic poles in respective rotors is
different, the current is actually ineffectual as it does not
create a torque in the other motor. This increases copper loss in
the motor.
[0006] It is therefore an object of this invention to suppress the
generation of an ineffectual current generated when two
motor/generators are driven independently by a single inverter.
[0007] It is a further object of this invention to control an
induced electromotive force generated by the rotations of the
motor/generator.
[0008] In order to achieve the above objects, this invention
provides a motor/generator comprising a first motor/generator unit
comprising a first rotor provided with a magnet and a first stator
provided with a plurality of coils facing the first rotor, and a
second motor/generator unit comprising a second rotor provided with
a magnet and a second stator provided with a plurality of coils
facing the second rotor.
[0009] The motor/generator is further configured as follows.
[0010] Providing that the number of coils in the first stator is
S1, the number of pairs of magnetic poles in the magnet of the
first rotor is P1, and the number of phases in a first alternating
current which drives the first rotor through the coils of the first
stator is M1, the coils of the first stator are divided into groups
of the number of K1 satisfying the equation K1=S1/M1. The coils in
each group of the first stator are mutually connected by either a Y
connection or a delta connection.
[0011] Providing that the number of coils in the second stator is
S2, the number of pairs of magnetic poles in the magnet of the
second rotor is P2, and the number of phases in a second
alternating current which drives the second rotor through the coils
of the second stator is M2, the coils of the second stator are
divided into groups of the number of K2 satisfying the equation
K2=S2/M2. The coils in each group of the second stator are mutually
connected by either a Y connection or a delta connection.
[0012] Providing that the groups of the first stator is numbered
from 1 to K1/A, A being a natural number, the coils in each group
of the first stator is numbered from 1 to M1, the groups of the
second stator is numbered from 1 to K2/B, B being a natural number,
the coils in each group of the second stator is numbered from 1 to
M2, and i and j are natural numbers, a coil with a coil number j in
a group number i of the first stator and a coil of a coil number i
in a group number j of the second stator are connected to each
other.
[0013] The details as well as other features and advantages of this
invention are set forth in the remainder of the specification and
are shown in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1A and 1B are schematic diagrams of motor/generators
according to this invention.
[0015] FIGS. 2A and 2B are schematic diagrams of rotors and stators
of the motor/generators.
[0016] FIG. 3 is a drive circuit diagram of the
motor/generators.
[0017] FIGS. 4A and 4B are similar to FIGS. 2A and 2B, but showing
a variation of the connecting structure of coils in the
stators.
[0018] FIGS. 5A and 5B are schematic diagrams of the stators
according to a second embodiment of this invention.
[0019] FIGS. 6A and 6B are schematic diagrams of stators and rotors
according to a third embodiment of this invention.
[0020] FIG. 7 shows a drive circuit diagram of motor/generators
according to the third embodiment of this invention.
[0021] FIGS. 8A and 8B are schematic diagrams of stators and rotors
according to a fourth embodiment of this invention.
[0022] FIG. 9 shows a drive circuit diagram of motor/generators
according to a fifth embodiment of this invention.
[0023] FIG. 10 is a diagram showing a relationship between an
impedance Z of an impedance component and a current/flowing in the
coils connected to the impedance component.
[0024] FIG. 11 is a diagram showing a relationship between the
impedance Z of the impedance component and an induced voltage
E.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] Referring to FIG. 1A of the drawings, a motor/generator 10
comprises a right motor/generator unit 10A and a left
motor/generator unit 10B housed in a single case 100. The right
motor/generator unit 10A is provided with a right rotor 42, a right
stator 40 and a right rotation shaft 44. The left motor/generator
unit 10B is provided with a left rotor 43, a left stator 41 and a
left rotation shaft 45.
[0026] The right rotation shaft 44 and the left rotation shaft 45
are disposed co-axially so that the right rotation shaft 44
overlaps with a part of the left rotation shaft 45. The right rotor
42 is provided with magnets having four pairs of magnetic
poles.
[0027] The left rotor 43 is provided with magnets having three
pairs of magnetic poles. Herein a pair of magnetic poles denotes a
pair of an N pole and S pole. Each of the right stator 40 and the
left stator 41 is provided with twelve coils in order to form a
rotating magnetic field. However the number of pairs of magnetic
poles of the rotating magnetic field in the right motor/generator
unit 10A differs from the number of pairs of poles of the rotating
magnetic field in the left motor/generator unit 10B.
[0028] The right stator 40 is so arranged that a magnetic field
having four pairs of magnetic poles is formed by supplying a
three-phase alternating current to the coils. The left rotor 41 is
so arranged that a magnetic field having three pairs of magnetic
poles is formed by supplying a four-phase alternating current to
the coils.
[0029] Referring to FIG. 1B, motor/generators 11 correspond to the
motor/generator 10 separated into two independent motor/generators.
Each motor/generator 11 is provided with a rotor 42(43), a stator
41(42) and a rotation 44(45). The structure of the rotor 42(43) and
the stator 40(41) is identical to those of the motor/generator
10.
[0030] Although this embodiment may be applied to the
motor/generator 10 or a pair of motor/generators 11, the following
description will describe an application to the motor/generator 10.
Referring now to FIGS. 2A and 2B, the right rotor 42 is provided
with magnets having four pairs of magnetic poles. The left rotor 43
is provided with a magnet having three pairs of magnetic poles.
Here the term "pairs of magnetic poles" refers to pairs of N poles
and S poles.
[0031] The right stator 40 and the left stator 41 are respectively
provided with twelve coils in order to form a rotating magnetic
field. However the number of pairs of magnetic poles in the
resultant rotating magnetic field in the right motor/generator unit
10A differs from the number in the left motor/generator unit 10B.
The right stator 40 of the right motor/generator unit 10A forms a
rotating magnetic field with four pairs of magnetic poles by
supplying a three-phase alternating current. The left stator 41 of
the left motor/generator unit 10B forms a rotating magnetic field
with three pairs of magnetic poles by supplying a four-phase
alternating current. The number of pairs of magnetic poles in the
rotating magnetic field formed by the stator 40(41) in order to
rotate the rotor 42(43) is equal to the number of pairs of magnetic
poles of the rotor 42(43).
[0032] The coils of the stator 40 are mutually connected as shown
in FIG. 2A. In the figure, the number of a coil is expressed by (i,
j). i is a group number. j is a number expressing the coil order in
the group or the phase number in a group. In the stator 40, there
are four groups of coils and each group is constituted by three
coils.
[0033] In the same manner, coils of the stator 41 are mutually
connected as shown in FIG. 2B. In the figure, the number of a coil
is expressed by (i, j) in the same manner as the stator 40. In the
stator 41, there are three groups of coils and each group is
constituted by four coils.
[0034] In the stator 40, each end of the three adjacent coils in
the same group forms a neutral point connected by a Y connection.
In the stator 41, each end of the four adjacent coils in the same
group forms a neutral point connected by a Y connection.
[0035] Referring now to FIG. 3, an alternating current from the
inverter 32 is supplied to the respective terminal of each coil
positioned on the opposite side to the neutral point. The inverter
is provided with twelve inverter units U1-U12. Each unit comprises
two transistors and two diodes. In total, the inverter 32 comprises
twenty four transistors Tr1-Tr24 and twenty four diodes D1-D24.
Twelve types of affirmative and negative pulse modulation signals
(hereafter referred to as a PWM signal) from a control circuit 33
are input into the base of the transistors Tr1-Tr24. A twelve
-phase alternating current can be output in response to the PWM
signal from each inverter unit U1-U12 of the inverter 32.
[0036] The coils of the stator 40 and 41 and the inverter 32 are
connected as shown in FIG. 3.
[0037] A coil (x, y) of the stator 40 and a coil (y, x) of the
stator 41 are connected to the same inverter unit U1-U12 of the
inverter 32. That is to say, a coil (1, 1) of the stator 40 and a
coil (1, 1) of the stator 41 are connected to the inverter unit U1.
A coil (1, 2) of the stator 40 and a coil (2, 1) of the stator 41
are connected to the inverter unit U2. A coil (1, 3) of the stator
40 and a coil (3, 1) of the stator 41 are connected to the inverter
unit U3. The other coils are connected to the inverter units U4-U12
in the same manner. Thus the coil (4, 3) of the stator 40 and the
coil (3, 4) of the stator 41 are connected to the inverter unit
U12.
[0038] The control of the output current of the inverter 32 will be
described below.
[0039] When the right motor/generator unit 10A is driven, in the
stator 40, an equiphase current is supplied to the four coils
(i,1), an equiphase current is supplied to the four coils (i, 2),
and an equiphase current is supplied to the four coils (i, 3). In
this manner, the stator 40 forms a rotating magnet field provided
with four pairs of magnetic poles by supplying respective
three-phase alternating currents to the four groups.
[0040] The same current is also applied to the coil (i, j) of the
stator 41 connected to each inverter unit U1-U12. However in the
stator 41, an equiphase current is applied to the four coils (1, j)
in the first group, an equiphase current is applied to the four
coils (2, j) in the second group and an equiphase current is
applied to the four coils (3, j) in the third group. Thus a current
does not flow in the coil (i, j) of the stator 41.
[0041] When the left motor/generator unit 10B is driven, in the
stator 41, an equiphase current is supplied to the three coils
(i,1), an equiphase current is supplied to the three coils (i, 2),
an equiphase current is supplied to the three coils (i, 3) and an
equiphase current is supplied to the three coils (i, 4). In this
manner, the stator 41 forms a rotating magnet field provided with
three pairs of magnetic poles by supplying four-phase alternating
currents to the three groups.
[0042] The same current is also applied to the stator 40 connected
to each inverter unit U1-U12. However in the stator 40, an
equiphase current is applied to the three coils (1, j) in the first
group, an equiphase current is applied to the three coils (2, j1)
in the second group, an equiphase current is applied to the four
coils (3, j) in the third group and an equiphase current is applied
to the four coils (4, j) in the fourth group. Thus a current does
not flow in the coil (i, j) of the stator 40.
[0043] When the right motor/generator unit 10A and the left
motor/generator unit 10B are driven at the same time, a composite
twelve-phase current combining the current flowing when the
respective motor/generators are driven is supplied to each pair of
coils, i.e., a coil (x, y) of the stator 40 and a coil (y, x) of
the stator 41, from each inverter unit U1-U12 of the inverter 32.
As a result, the same current is applied to each pair of coils, but
a current component to drive the rotor 43 does not flow in the
coils of the stator 40 which drives the rotor 42 and a current
component to drive the rotor 42 does not flow in the coils of the
stator 41 which drives the rotor 43.
[0044] Thus in the motor/generator 10 the current supplied to the
stator 40(41) to drive one of the rotors 42(43) does not flow at
all in the coils of the stator 41(40) which drives the other rotor
43(42). As a result, an ineffectual current is not generated.
[0045] Although the motor/generator 10 has been described above,
the same wiring can be applied to the stators 40 and 41 of two
independent motor/generators 11.
[0046] In this embodiment, the coils of the stators 40 and 41 in
the same group are connected by a Y connection. However as shown in
FIGS. 4A and 4B, it is possible to connect the coils in the same
group with a delta connection which is equivalent to a Y
connection.
[0047] In this embodiment, the number of coils S1(S2) of the stator
40(41) of the right motor/generator unit 10A (left motor/generator
unit 10B), the number of pairs of magnetic poles P1(P2) of the
rotor 42(43) and the phase number M1(M2) of the alternating current
supplied to the coils (i, j) of the stator 40(41) are summarized as
follows.
[0048] right motor/generator unit 10A: S1=12, P1=4, M1=3
[0049] left motor/generator unit 10B: S1=12, P1=3, M2=4
[0050] A second embodiment of this invention will be described with
reference to FIGS. 5A and 5B.
[0051] In the first embodiment, the groups were constituted by
connecting adjacent coils with a Y connection. In this embodiment,
groups are constituted by connecting coils disposed at a fixed
angular interval with a Y connection.
[0052] Stators 40A and 41A in this embodiment are also provided
with twelve coils. The stator 40A forms a rotating magnetic field
provided with four pairs of magnetic poles due to the supply of a
three-phase alternating current. The stator 41A forms a rotating
magnetic field provided with three pairs of magnetic poles due to
the supply of a four-phase alternating current.
[0053] This embodiment differs from the first embodiment with
respect to the connection to the neutral point. In the stator 40A
of this embodiment, a single group is formed by connecting three
coils disposed at 120-degree intervals to the neutral point by a Y
connection. In the stator 41A of this embodiment, a single group is
formed by connecting four coils disposed at 90-degree intervals to
the neutral point by a Y connection. The structure of the drive
circuit is the same as that in the first embodiment.
[0054] In this embodiment, when the right motor /generator unit 10A
is driven, in the stator 40A, an equiphase current is supplied to
the four coils (i, 1), an equiphase current is supplied to the four
coils (i, 2), and an equiphase current is supplied to the four
coils (i, 3). As a result, in the stator 41A, an equiphase current
is applied to the four coils (1, j) in the first group, an
equiphase current is applied to the four coils (2, j) in the second
group and an equiphase current is applied to the four coils (3, j)
in the third group. Thus a current does not flow in the coils (i,
j) of the stator 41A.
[0055] On the other hand, when the left motor/generator unit 10B is
driven, in the stator 41A, an equiphase current is supplied to the
three coils (i,1), an equiphase current is supplied to the three
coils (i, 2), an equiphase current is supplied to the three coils
(i, 3) and an equiphase current is supplied to the three coils (i,
4). As a result, in the stator 40A, an equiphase current is applied
to the three coils (1, j) in the first group, an equiphase current
is applied to the three coils (2, j) in the second group, an
equiphase current is applied to the four coils (3, j) in the third
group and an equiphase current is applied to the four coils (4, j)
in the fourth group. Thus a current does not flow in the coil (i,
j) of the stator 40A.
[0056] Thus this embodiment also prevents the generation of an
ineffectual current. A third embodiment of this invention will be
described with reference to FIGS. 6A and 6B and FIG. 7. The stators
40B and 41B in this embodiment are respectively provided with nine
coils (i, j). The rotor 42B and 43B is provided with magnets having
three pairs of magnetic poles. In the stator 40B, three adjacent
coils are connected with a Y connection to provide a neutral point.
In the stator 41B, three adjacent coils are connected with a Y
connection in the same manner to provide a neutral point. Thus the
coils of the stators 40B and 41B are respectively divided into
three groups.
[0057] An inverter 32B to supply composite alternating current to
the coils of the stator 40B and 41B comprises nine inverter units
U1-U9. The inverter 32B and the coils of the stators 40B and 41B
are connected as shown in FIG. 7.
[0058] A coil (x, y) of the stator 40B and a coil (y, x) of the
stator 41B are connected to the same inverter unit U1-U9. That is
to say, a coil (1, 1) of the stator 40B and a coil (1, 1) of the
stator 41B are connected to the inverter unit U3. A coil (1, 2) of
the stator 40B and a coil (2, 1) of the stator 41B are connected to
the inverter unit U2. A coil (1, 3) of the stator 40B and a coil
(3, 1) of the stator 41B are connected to the inverter unit U1. A
coil (2, 1) of the stator 40B and a coil (1, 2) of the stator 41B
are connected to the inverter unit U6. A coil (2, 2) of the stator
40B and a coil (2, 2) of the stator 41B are connected to the
inverter unit U5. A coil (2, 3) of the stator 40B and a coil (3, 2)
of the stator 41B are connected to the inverter unit U4. A coil
(3,1) of the stator 40B and a coil (1, 3) of the stator 41B are
connected to the inverter unit U9. A coil (3,2) of the stator 40B
and a coil (2, 3) of the stator 41B are connected to the inverter
unit U8. A coil (3,3) of the stator 40B and a coil (3, 3) of the
stator 41B are connected to the inverter unit U7.
[0059] In this embodiment, when the right motor/generator unit 10A
is driven, a three-phase alternating current is supplied to three
coils in the same group of the stator 40B. As a result, in the
stator 40B, an equiphase current is supplied to the three coils (i,
1), an equiphase current is supplied to the three coils (i, 2), and
an equiphase current is supplied to the three coils (i, 3). Thus
the stator 40 forms a rotating magnetic field provided with three
pairs of magnetic poles.
[0060] The same current is also applied to the coil (i, j) of the
stator 41B connected to each inverter unit U1-U9. However in the
stator 41 B, an equiphase current is applied to the three coils
(1,j) in the first group, an equiphase current is applied to the
three coils (2,j) in the second group and an equiphase current is
applied to the three coils (3, j) in the third group. Thus a
current does not flow in the coils (ij) of the stator 41B.
[0061] When the left motor/generator unit 10B is driven, a
three-phase alternating current is supplied to three coils in the
same group of the stator 41B. As a result, in the stator 41B, an
equiphase current is supplied to the three coils (i, 1), an
equiphase current is supplied to the three coils (i, 2), and an
equiphase current is supplied to the three coils (i, 3). Thus the
stator 41B forms a rotating magnetic field provided with three
pairs of magnetic poles.
[0062] The same current is also applied to the coil of the stator
40B connected to each inverter unit U1-U9. However in the stator
40B, an equiphase current is applied to the three coils (1,j) in
the first group, an equiphase current is applied to the three coils
(2,j) in the second group and an equiphase current is applied to
the three coils (3, j) in the third group. Thus a current does not
flow in the coils (i,j) of the stator 40B.
[0063] Thus in the motor/generator 10(11), the current supplied to
the stator 40B(41B) to drive one of the rotors 42(43) does not flow
at all in the coils of the stator 41B(40B) which drives the other
rotor 43(42). As a result, an ineffectual current is not
generated.
[0064] In this embodiment, the coils are connected by a Y
connection. However it is possible to connect the coils with a
delta connection which is equivalent to a Y connection.
[0065] In this embodiment, the number of coils S 1(S2) of the
stator 40B(41B) of the right motor/generator unit 10A (left motor
/generator unit 10B), the number of pairs of magnetic poles P1(P2)
of the rotor 42(43) and the phase number M1(M2) of the alternating
current supplied to the coils (i, j) of the stator 40B(41B) are
summarized as follows.
[0066] right motor/generator unit 10A: S1=9, P1=3, M1=3
[0067] left motor/generator unit 10B: S1=9, P1=3, M2=3
[0068] A fourth embodiment of this invention will be described with
reference to FIGS. 8A and 8B.
[0069] The stator 40C according to this embodiment is provided with
eighteen coils (i, j). The rotor 42C is provided with a magnet
having six pairs of magnetic poles. The structure of the control
circuit, the inverter and the stator 41C and rotor 43C is the same
as that described with reference to the third embodiment.
[0070] Three adjacent coils of the stator 40C are connected with a
Y connection to provide a neutral point. Thus six neutral points
are provided in the stator 40C.
[0071] Further, the coils of two adjacent groups are connected in
parallel to the inverter.
[0072] For example, two coils (1, 1) of the first group and the
second group are connected to the inverter unit U3 of the inverter
32B of the third embodiment. The coil (1, 1) of the stator 41C is
also connected to the inverter unit U3.
[0073] In this manner, two coils (x, y) of the stator 40C and one
coil (y, x) of the stator 41C are connected to the same inverter
unit U1-U9.
[0074] In this embodiment, when the right motor/generator unit 10A
is driven, a three-phase alternating current is supplied to six
coils (i,1) of the first and second groups, to six coils (i,2) of
the third and fourth groups, and to six coils (i,3) of the fifth
and sixth groups in the stator 40C. As a result, in the stator 40C,
an equiphase current is supplied to the six coils (i, 1), an
equiphase current is supplied to the six coils (i, 2) and an
equiphase current is supplied to the six coils (i, 3). Thus the
stator 40C forms a rotating magnetic field provided with six pairs
of magnetic poles.
[0075] In this case, the same current is applied to the coils of
the stator 41C which is connected to each inverter unit U1-U9.
However in the stator 41C, an equiphase current is applied to the
three coils (1, j) of the first group, an equiphase current is
applied to the three coils (2, j) of the second group, and an
equiphase current is applied to the three coils (3, j) of the third
group. Thus a current does not flow in the coil (i, j) of the
stator 41C.
[0076] On the other hand, when the left motor/generator unit 10B is
driven, in the stator 41C, a three-phase alternating current is
supplied to the three coils in the same group of the stator 41C. As
a result in the stator 41C, an equiphase current is supplied to the
three coils (i,1), an equiphase current is supplied to the three
coils (i, 2), and the same phase is supplied to the three coils (i,
3). Thus the stator 41B forms a rotating magnetic field provided
with three pairs of magnetic poles.
[0077] The same current is applied to the coils of the stator 40C
connected to each inverter unit U1-U9. However in the stator 40C,
an equiphase current is applied to the six coils (1, j) of the
first and second groups, an equiphase current is applied to the six
coils (2, j) of the third and fourth groups, and an equiphase
current is applied to the six coils (3, j) of the fifth and sixth
groups. Thus a current does not flow in the coil (i, j) of the
stator 40C.
[0078] Thus in the motor/generator 10(11), the current supplied to
the stator 40C(41C) to drive one of the rotors 42C(43C) does not
flow at all in the coils of the stator 41C(40C) which drives the
other rotor 43C(42C). As a result, an ineffectual current is not
generated.
[0079] In this embodiment, the coils are connected by a Y
connection. However it is possible to connect the coils with a
delta connection which is equivalent to a Y connection.
[0080] In this embodiment, the number of coils S1(S2) of the stator
40C(41C) of the right motor/generator unit 10A (left
motor/generator unit 10B), the number of pairs of magnetic poles
P1(P2) of the rotor 42C(43C) and the phase number M1(M2) of the
alternating current supplied to the coils (i, j) of the stator
40C(41C) are summarized as follows.
[0081] right motor/generator unit 10A: S1=18, P1=6, M1=3
[0082] left motor/generator unit 10B: S1=9, P1=3, M2=3
[0083] A fifth embodiment of this invention will be described with
reference to FIGS. 9 to 11 and FIGS. 12A and 12B.
[0084] In this embodiment, neutral points A1, B1, C1, D1 of the
coils in the first to fourth groups of the first stator 40 of the
second embodiment are earthed through respective impedance
components Z1-Z4 as shown in FIG. 9. Furthermore neutral points A2,
B2, C2 of the coils in the first to third groups of the second
stator 41 of the second embodiment are earthed through respective
impedance components Z5-Z7.
[0085] In other respects, the fifth embodiment is the same as the
second embodiment.
[0086] FIG. 10 shows the relationship between impedance Z of the
impedance components Z1-Z7 and the ineffectual current I2 and the
effectual current I1 of the coil (i, j).
[0087] When the neutral point of the coils is not earthed as in the
case of the first to fourth embodiments, the impedance Z of the
impedance components Z1-Z7 is equal to an infinite value. In this
case, the ineffectual current I2 flowing in the coil is zero and
the entire current flowing in the coils becomes the effectual
current I1.
[0088] On the other hand, when the neutral point is directly
earthed, the impedance Z of the impedance components Z1-Z7 is equal
to zero. In this case, the ineffectual current I2 as shown in the
figure exceeds the effectual current I1.
[0089] Thus it is possible to arbitrarily set the ratio of
effectual current I1 and the ineffectual current I2 by setting the
impedance Z of the impedance components Z1-Z7. Although it is
preferred to maximize the impedance Z in terms of energy
efficiency, allowing an arbitrary setting of the effectual current
I1 and the ineffectual current I2 has the following advantages.
[0090] In the motor/generator 10 according to the first to fourth
embodiments, the alternating current driving the motor/generator
unit 10A is also applied to the motor/generator unit 10B. However
the current applied to the coils in the same group of the
motor/generator unit 10B is all equiphase.
[0091] In this case, the neutral points of the coils are not
earthed and not connected with each other.
[0092] There is no current to the outside from the neutral points.
Thus even when an equiphase alternating current is applied to all
the coils of the same group which is connected by a Y connection to
the neutral point, there is no current in the coils.
[0093] In other words, the alternating current which drives the
motor /generator unit 10A does not flow in the coils of the
motor/generator unit 10B. In the same manner, the alternating
current which drives the motor /generating unit 10B does not flow
in the coils of the motor/generator unit 10A.
[0094] The composite current which drives the motor/generator units
10A and 10B requires a total potential difference of E1+E2. The
potential difference E1 exists between the output terminals of the
inverter 32 required to drive the motor/generator unit 10A and the
neutral points of the coils of the motor/generator unit 10A. The
potential difference E2 exists between the output terminals of the
inverter 32 required to drive the motor/generator unit 10B and the
neutral points of the coils of the motor/generator unit 10B.
[0095] In other words, the potential of the neutral points of the
coils of the motor/generator unit 10A is E2 and the potential of
the neutral points of the coils of the motor/generator unit 10B is
E1. This is equivalent to connecting the coils of the
motor/generator unit 10A and the coils of the motor/generator unit
10B in series to the output terminal of the inverter 32.
[0096] An induced electromotive force is generated in these coils
by the rotation of the motor/generator units 10A and 10B. The
induced electromotive force increases with increases in the
rotation speed of the motor/generator units 10A and 10B. When the
sum of the induced electromotive force in the motor/generator units
10A and 10B exceeds the voltage of the output terminals of the
inverter 32, current does not flow to the motor/generator units 10A
and 10B from the inverter 32, and operation of the motor/generator
units 10A and 10B is no longer possible.
[0097] It is possible to control the induced electromotive force by
earthing the coils of each group of the motor/generator units 10A
and 10B through the impedance components Z1-Z7. FIG. 11 shows the
relationship of the induced voltage E and the impedance Z of the
impedance components Z1-Z7. As clearly shown in the figure, it is
possible to prevent the induction voltage E from over-increasing by
setting the impedance Z of the impedance components Z1-Z7.
[0098] The contents of Tokugan Hei 11-351613 with a filing date of
Dec. 10, 1999 in Japan, and Tokugan 2000-358004 with a filing date
of Nov. 27, 2000 in Japan, are hereby incorporated by
reference.
[0099] Although the invention has been described above by reference
to certain embodiments of the invention, the invention is not
limited to the embodiments described above. Modifications and
variations of the embodiments described above will occur to those
skilled in the art, in light of the above teachings.
[0100] The embodiments of this invention in which an exclusive
property or privilege is claimed are defined as follows:
* * * * *