FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ELECTRIC VEHICLE CONTROL DEVICE;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED
AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
5 Field
[0001] The present invention relates to an electric
vehicle control device that controls multiple induction
motors with a single inverter.
10 Background
[0002] Wayside devices serving as a receiver of various
types of signals are provided along a track on which
electric vehicles run. To prevent malfunction of these
wayside devices, electric vehicles are subject to
15 regulations regarding leakage noise. Patent Literature 1
given below describes that a hollow core made of
ferromagnetic material such as ferrite or amorphous metal
is provided around the wiring between an inverter and an
electric motor (hereinafter, simply motor), which is a load,
20 to reduce common mode noise.
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
25 Laid-open No. 2004-187368
Summary
Technical Problem
[0004] Unfortunately, an electric vehicle has limited
30 underfloor space. In some case, there is not a sufficient
space for additional installation of filter elements such
as the cores described in Patent Literature 1. In such a
case, the specifications of the electric vehicle control
3
device may be reconsidered in order to provide a space for
additional installation of filter elements.
[0005] The filtering characteristic of a filter element
needs to be determined in accordance with the impedance
5 including that of the induction motor. The manufacturer of
the induction motor is not necessarily the same as the
manufacturer of the electric vehicle control device. In
this case, relying on additional installation of filter
elements will increase designing manpower for the
10 manufacturer of the electric vehicle control device, and
increase adjustment work on practical vehicles. It is thus
desired to reduce or eliminate leakage noise without
relying on additional installation of filter elements.
[0006] The present invention has been made in view of
15 the foregoing, and it is an object of the present invention
to provide an electric vehicle control device capable of
reducing or eliminating leakage noise without relying on
additional installation of filter elements.
20 Solution to Problem
[0007] To solve the problem and achieve the object
described above, the present invention is an electric
vehicle control device to control a plurality of induction
motors with a single inverter. The electric vehicle
25 control device comprising: a first inverter to control a
first electric motor group defined by a plurality of
induction motors; and a second inverter to control a second
electric motor group defined by a plurality of induction
motors. The induction motors belonging to the first
30 electric motor group are mounted on different bogies, and
the induction motors belonging to the second electric motor
group are mounted on different bogies. The first inverter
and the induction motors belonging to the first electric
4
motor group are connected to each other by a first
conductor, and the second inverter and the induction motors
belonging to the second electric motor group are connected
to each other by a second conductor. Between each of the
5 first and second inverters and the bogies, a first length
is equal to or less than three times an average value of a
second length and a third length, the first length being an
inter-center distance between the first conductor and the
second conductor, the second length being a maximum length
10 of a conductor portion of the first conductor in a cross
section of the first conductor, the third length being a
maximum length of a conductor portion of the second
conductor in a cross section of the second conductor.
15 Advantageous Effects of Invention
[0008] The electric vehicle control device according to
the present invention provides an advantage that the
leakage noise can be reduced or eliminated without relying
on the additional installation of the filter elements.
20
Brief Description of Drawings
[0009] FIG. 1 is a diagram illustrating a circuit
configuration of an electric vehicle control device
according to a first embodiment.
25 FIG. 2 is a diagram illustrating a circuit
configuration of a typical conventional electric vehicle
control device.
FIG. 3 is a diagram illustrating a typical
conventional example arrangement of induction motors in an
30 electric vehicle.
FIG. 4 is a diagram illustrating an example
configuration of a typical conventional inverter main
circuit.
5
FIG. 5 is a diagram for use in describing a technique
for generating a pules width modulation (PWM) control
signal to be provided to the semiconductor devices of each
arm illustrated in FIG. 4.
5 FIG. 6 is a diagram illustrating PWM control signals
generated by the individual phase voltage commands
illustrated in FIG. 5.
FIG. 7 is a diagram illustrating an equivalent circuit
of FIG. 2, for use in describing a leakage current.
10 FIG. 8 is a diagram illustrating a common mode voltage
caused by the PWM control signals illustrated in FIG. 6.
FIG. 9 is a diagram illustrating an example
configuration of an inverter main circuit according to the
first embodiment.
15 FIG. 10 is a diagram illustrating an example
arrangement of the induction motors in the first embodiment.
FIG. 11 is a set of diagrams for use in describing
variations of the voltage command provided to the leg of
each phase of each group in the first embodiment.
20 FIG. 12 is a diagram illustrating PWM control signals
generated by the individual phase voltage commands
illustrated in FIG. 11(a).
FIG. 13 is a diagram of an equivalent circuit of the
circuit of FIG. 1, for use in describing a leakage current
25 in the first embodiment.
FIG. 14 is a diagram for use in describing an interconductor distance in the first embodiment.
FIG. 15 is a diagram illustrating a circuit
configuration of an electric vehicle control device
30 according to a comparative example for the circuit
configuration of FIG. 1.
FIG. 16 is a diagram illustrating an example
arrangement of the induction motors, different from the
6
arrangement of in FIG. 10, in the first embodiment.
FIG. 17 is a diagram illustrating an example
configuration of a cooling device in the first embodiment.
FIG. 18 is a diagram illustrating an in-vehicle
5 configuration of an electric vehicle control device
according to a second embodiment.
FIG. 19 is a diagram illustrating an in-vehicle
configuration of an electric vehicle control device
according to a variation of the second embodiment.
10 FIG. 20 is a diagram illustrating a configuration of
and around a bogie of an electric vehicle control device
according to a third embodiment.
FIG. 21 is a diagram illustrating a configuration of
an inverter connection unit of an electric vehicle control
15 device according to a fourth embodiment.
FIG. 22 is a block diagram illustrating an example of
hardware configuration that implements the functionality of
the control unit in the first embodiment through the fourth
embodiment.
20 FIG. 23 is a block diagram illustrating another
example of hardware configuration that implements the
functionality of the control unit in the first embodiment
through the fourth embodiment.
25 Description of Embodiments
[0010] An electric vehicle control device according to
embodiments of the present invention will be described in
detail below with reference to the accompanying drawings.
Note that the following embodiments are not intended to
30 limit the scope of the present invention. Note also that
the accompanying drawings are not necessarily drawn to
scale, and neither are diagrams in different figures.
[0011] First Embodiment.
7
FIG. 1 is a diagram illustrating a circuit
configuration of an electric vehicle control device
according to a first embodiment. An electric vehicle
control device 10 according to the first embodiment
5 includes, as illustrated in FIG. 1, a capacitor 11, a first
inverter 121, a second inverter 122, and a control unit 20.
The first inverter 121 is connected, by a first conductor
141, to two induction motors 181 and 182 belonging to a
first motor group 161. The second inverter 122 is
10 connected, by a second conductor 142, to two induction
motors 183 and 184 belonging to a second motor group 162.
The four induction motors 181, 182, 183, and 184 are each a
main motor for driving the electric vehicle.
[0012] The first conductor 141 is electrical wiring for
15 electrically interconnecting the first inverter 121 and the
two induction motors 181 and 182. The second conductor 142
is electrical wiring for electrically interconnecting the
second inverter 122 and the two induction motors 183 and 184.
The first conductor 141 and the second conductor 142 may be
20 made of any electrically conductive material that can
provide electrical connection.
[0013] The first inverter 121 and the second inverter
122 are housed in the same enclosure 6. The enclosure 6
includes a positive terminal P and a negative terminal N.
25 [0014] Note that the following description may refer to
the first inverter 121 and the second inverter 122 as
“inverter 12” or “inverters 12” when no distinction is made
therebetween, and the induction motors 181, 182, 183, and
184 as “induction motor 18” or “induction motors 18” when
30 no distinction is made therebetween.
[0015] An overhead line 1 supplies direct current (DC)
power though a current collector unit 2 and a reactor 5 to
the electric vehicle control device 10. There is an
8
electric power substation (not illustrated) beyond the
overhead line 1, and the overhead line 1 serves as an
external power supply for the electric vehicle control
device 10. Note that the voltage of the overhead line 1,
5 i.e., the trolley voltage, applied to the current collector
unit 2, and conversion capacities in the electric vehicle
control device 10 depend on the drive method. The trolley
voltage ranges approximately from 600 to 3000 [V], and the
conversion capacities each range from several tens to
10 several hundred kilovolt-amperes [kVA].
[0016] The positive terminal P of the electric vehicle
control device 10 is connected to the reactor 5. The
negative terminal N of the electric vehicle control device
10 is electrically connected to a rail 4 via a wheel 3.
15 This configuration allows a DC current of the DC power
supplied from the overhead line 1 to flow through the
reactor 5, the electric vehicle control device 10, the
wheel 3, and the rail 4, and then return to the electric
power substation.
20 [0017] Note that although FIG. 1 illustrates the
overhead line 1 as an aerial electrical line, and the
current collector unit 2 as a current collector unit having
a pantograph shape, these elements are not limited thereto.
The overhead line 1 may be a third rail used in a subway or
25 the like, and the current collector unit 2 may be a current
collector unit suitable for such a third rail. In addition,
although FIG. 1 illustrates the overhead line 1 as a DC
overhead line, the overhead line 1 may be an alternating
current (AC) overhead line. Note that in a case in which
30 the overhead line 1 is an AC overhead line, a transformer
is provided in place of the reactor 5 to step down the AC
voltage received, and a converter is provided downstream of
the transformer to convert the AC voltage output from the
9
transformer into a DC voltage.
[0018] The capacitor 11 is connected between the
positive terminal P and the negative terminal N inside the
electric vehicle control device 10. The capacitor 11 is
5 connected in parallel to both ends of the first inverter
121 on the input side of the first inverter 121 and to both
ends of the second inverter 122 on the input side of the
second inverter 122.
[0019] The capacitor 11 smooths the DC voltage applied.
10 In addition, the capacitor 11 is connected to the reactor 5,
and forms an LC filter circuit with the reactor 5. This LC
filter circuit provides protection against a surge voltage
applied from the overhead line 1. The LC filter circuit
also reduces the amplitude of the ripple component of the
15 current flowing to the inverters 12. The inverters 12 are
each a power conversion circuit that supplies electrical
power to the corresponding induction motors 18. The
inverters 12 each operate to convert the DC voltage across
the capacitor 11 into an AC voltage having some voltage
20 value and having some frequency to apply the AC voltage to
corresponding ones of the induction motors 18 under control
of the control unit 20.
[0020] FIG. 2 is a diagram illustrating a circuit
configuration of a typical conventional electric vehicle
25 control device. In FIG. 2, like reference characters
designate elements corresponding to elements illustrated in
FIG. 1.
[0021] An electric vehicle control device according to
conventional technology is typically configured such that,
30 as illustrated in FIG. 2, a single inverter 12 controls all
of four induction motors 18. In a case in which the main
motors are induction motors, a slip, i.e., a difference
between the rotational frequency and the drive voltage
10
frequency, results in generation of torque. The slip
unique to an induction motor can be used to enable a single
inverter to control multiple main motors in parallel.
[0022] FIG. 3 is a diagram illustrating a typical
5 conventional example arrangement of induction motors in an
electric vehicle. In FIG. 3, like reference characters
designate elements corresponding to elements illustrated in
FIG. 2.
[0023] As illustrated in FIG. 3, the four induction
10 motors 18 are mounted in two bogies 24 each of which
includes two of the four induction motors 18. The
configuration is such that each of the bogies 24 is
supported by two axles 56, and a vehicle 40 is supported by
the two bogies 24. The torque generated on the four
15 induction motors 18 is transferred to the axles 56 via a
decelerator (not illustrated), and acts to propel the
vehicle 40.
[0024] FIG. 4 is a diagram illustrating an example
configuration of a typical conventional inverter main
20 circuit. The inverter main circuit includes semiconductor
devices UPI, VPI, and WPI of upper arms and semiconductor
devices UNI, VNI, and WNI of lower arms. Note that as a
single semiconductor device could provide insufficient
current capacity, each arm in FIG. 4 includes two
25 semiconductor devices connected in parallel with each other.
The semiconductor devices connected in parallel with each
other are given the same control signal.
[0025] The pair of semiconductor devices UPI and the
pair of semiconductor devices UNI are connected in series
30 with each other to form a phase-U leg. The pair of
semiconductor devices VPI and the pair of semiconductor
devices VNI are connected in series with each other to form
a phase-V leg. The pair of semiconductor devices WPI and
11
the pair of semiconductor devices WNI are connected in
series with each other to form a phase-W leg. The phase-U,
phase-V, and phase-W legs are connected in parallel with
one another to form a three-phase bridge circuit. The
5 semiconductor devices connected in parallel with each other
in each arm are given the same control signal.
[0026] FIG. 5 is a diagram for use in describing a
technique for generating a PWM control signal to be
provided to the semiconductor devices of each arm
10 illustrated in FIG. 4. FIG. 5 illustrates a phase-U
voltage command 26U, a phase-V voltage command 26V, and a
phase-W voltage command 26W, each of which is a sine wave;
and a carrier 28 that is a triangular wave. The horizontal
axis represents the phase angle, and the vertical axis
15 represents the amplitude value. A value of 1 [Vpu] along
the vertical axis is equivalent to a half (1/2) of the
amplitude of the voltage applied to the inverters 12. That
is, the value of 1 [Vpu] is equivalent to 1/2 of the DC
voltage that is the voltage across the capacitor 11.
20 [0027] FIG. 6 is a diagram illustrating PWM control
signals generated by the individual phase voltage commands
illustrated in FIG. 5. FIG. 6 illustrates a phase-U PWM
control signal, a phase-V PWM control signal, and a phase-W
PWM control signal in that order from the top. The
25 horizontal axis of FIG. 6 represents the phase angle, as in
FIG. 5.
[0028] The control unit 20 compares the phase-U voltage
command 26U and the triangular wave signal, i.e., the
carrier 28. The phase-U PWM control signal becomes “ON”
30 with the phase-U voltage command 26U greater than the
carrier 28, and becomes “OFF” with the phase-U voltage
command 26U less than or equal to carrier 28. The thus
generated phase-U PWM control signal is illustrated in the
12
top portion of FIG. 6. The phase-V PWM control signal and
the phase-W PWM control signal are also generated by
comparison of each of the phase-V voltage command 26V and
the phase-W voltage command 26W with the carrier 28, as in
5 the phase-U PWM control signal. The phase-V PWM control
signal and the phase-W PWM control signal generated in this
manner are illustrated in the middle and bottom portions of
FIG. 6, respectively.
[0029] FIG. 7 is a diagram illustrating an equivalent
10 circuit of FIG. 2, for use in describing a leakage current.
FIG. 7 illustrates the induction motor 18, using a set of
circuit symbols of inductor. Three-phase motors, which are
not to limited to dielectric motors, have neutral point
potentials varying when driven with three-phase inverters.
15 This results in an equivalent circuit, as illustrated in
FIG. 7, in which a stray capacitor 34 is connected between
a neutral point potential 32 of the induction motor 18 and
a reference potential 31 that is the ground potential. The
neutral point potential 32 contains a high-frequency
20 component caused by PWM control. As a result of
application of a phase-U voltage 33U, a phase-V voltage 33V,
and a phase-W voltage 33W to the induction motor 18,
therefore, a leakage current 35 flows through the stray
capacitor 34.
25 [0030] Note that the potential difference between the
neutral point potential 32 and the reference potential 31
is called “common mode voltage”. In the case of a threephase inverter, the common mode voltage is calculated by
(Vu+Vv+Vw)/3, where Vu is the amplitude of the phase-U
30 voltage 33U, Vv is the amplitude of the phase-V voltage 33V,
and Vw is the amplitude of the phase-W voltage 33W.
[0031] FIG. 8 is a diagram illustrating a common mode
voltage caused by the PWM control signals illustrated in
13
FIG. 6. In FIG. 8, the horizontal axis represents the
phase angle, and the vertical axis represents the amplitude
of the common mode voltage.
[0032] A leakage current flows each time the common mode
5 voltage changes. In addition, as illustrated in FIG. 8,
the common mode voltage varies in a period shorter than the
period of the carrier. This shows that a reduction in the
leakage current 35 flowing through the stray capacitor 34
is important for reduction or elimination of leakage noise.
10 [0033] FIG. 9 is a diagram illustrating an example
configuration of an inverter main circuit according to the
first embodiment. The inverter main circuit according to
the first embodiment includes the first inverter 121 and
the second inverter 122. The first inverter 121 and the
15 second inverter 122 are connected , on the input side
thereof, to both ends of the capacitor 11 in parallel.
[0034] The first inverter 121 includes a phase-U leg 22U,
a phase-V leg 22V, and a phase-W leg 22W that correspond to
three phases, and each leg has the semiconductor device of
20 the upper arm and the semiconductor device of the lower arm
that are connected in series with each other. The phase-U
leg 22U, the phase-V leg 22V, and the phase-W leg 22W are
connected in parallel with one another to form a threephase bridge circuit.
25 [0035] The second inverter 122 includes a phase-X leg
22X, a phase-Y leg 22Y, and a phase-Z leg 22Z that
correspond to three phases, and each leg has the
semiconductor device of the upper arm and the semiconductor
device of the lower arm that are connected in series with
30 each other. The phase-X leg 22X, the phase-Y leg 22Y, and
the phase-Z leg 22Z are connected in parallel with one
another to form a three-phase bridge circuit.
[0036] As long as the total capacitance of the three-
14
phase motors is unchanged, the number of the semiconductor
devices to be used may also be the same. Twelve
semiconductor devices are used in both the conventional
example and the first embodiment. While the conventional
5 example illustrated in FIG. 4 is characterized in that each
arm has a parallel configuration, the first embodiment
illustrated in FIG. 9 is characterized in that the
inverters are connected in parallel.
[0037] FIG. 10 is a diagram illustrating an example
10 arrangement of the induction motors in the first embodiment.
In FIG. 10, like reference characters designate elements
corresponding to elements illustrated in FIG. 1.
[0038] In FIG. 10, the first inverter 121 and the second
inverter 122 are disposed under the floor in a central
15 portion of the vehicle 40, and are housed in the enclosure
6. In addition, the two induction motors 181 and 182
belonging to the first motor group 161 are mounted on a
first bogie 241 and a second bogie 242, respectively.
Similarly, the two induction motors 183 and 184 belonging
20 to the second motor group 162 are also mounted on the first
bogie 241 and the second bogie 242, respectively. That is,
one induction motor 181 belonging to the first motor group
161 and one induction motor 183 belonging to the second
motor group 162 are mounted on the first bogie 241, and the
25 other induction motor 182 belonging to the first motor
group 161 and the other induction motor 184 belonging to
the second motor group 162 are mounted on the second bogie
242.
[0039] According to the above arrangement, the first
30 conductor 141 is installed between first bogie 241 and the
second bogie 242 via the first inverter 121 disposed in a
central portion of the vehicle 40. The second conductor
142 is also installed between the first bogie 241 and the
15
second bogie 242 via the second inverter 122 disposed in a
central portion of the vehicle 40. When the first
conductor 141 and the second conductor 142 are installed,
the first conductor 141 and the second conductor 142 are
5 arranged close to each other. Note that a description will
be made later as to how small the inter-distance between
the first conductor 141 and the second conductor 142 should
be when the first conductor 141 and the second conductor
142 are arranged.
10 [0040] FIG. 11 is a set of diagrams for use in
describing variations of the voltage command provided to
the leg of each phase of each group in the first embodiment.
Parts (a) to (c) of the top portion of FIG. 11 illustrate
patterns of the different groups of phases rotating in the
15 same direction. Parts (d) to (f) of the bottom portion of
FIG. 11 illustrate patterns of the different groups of
phases rotating in the opposite directions.
[0041] In FIG. 11, the symbol “U” represents the voltage
command of phase U, which is a first phase of the first
20 inverter 121. Similarly, the symbol “V” represents the
voltage command of phase V, which is a second phase of the
first inverter 121, and the symbol “W” represents the
voltage command of phase W, which is a third phase of the
first inverter 121.
25 [0042] The voltage command for each phase is a vector,
whose rotational direction is defined as the
counterclockwise direction with respect to phase U. In
addition, the vectors of phases U,V,W rotate in the order
of U,V,W. Accordingly, the vector of phase V lags 120
30 degrees behind that of phase U in the rotational direction,
and the vector of phase W lags 120 degrees behind that of
phase V (i.e., 240 degrees behind that of phase U) in the
rotational direction.
16
[0043] In addition, the symbol “X” represents the
voltage command of phase X, which is a first phase of the
second inverter 122. Similarly, the symbol “Y” represents
the voltage command of phase Y, which is a second phase of
5 the second inverter 122, and the symbol “Z” represents the
voltage command of phase Z, which is a third phase of the
second inverter 122.
[0044] The voltage command for each phase is a vector,
whose rotational direction is defined as the
10 counterclockwise direction with respect to phase X. In
addition, the vectors of phases X,Y,Z rotate in the order
of X,Y,Z. Accordingly, the vector of phase Y lags 120
degrees behind that of phase X in the rotational direction,
and the vector of phase Z lags 120 degrees behind that of
15 phase Y (i.e., 240 degrees behind that of phase X) in the
rotational direction.
[0045] FIG. 11(a) illustrates an example in which the
vectors of phase-U and phase-X are in opposite directions,
that is, the vector of phase-X is 180 degrees out of phase
20 with that of phase-U. FIG. 11(b) illustrates an example in
which the vectors of phase-U and phase-Y are in opposite
directions, that is, the vector of phase-Y is 180 degrees
out of phase with that of phase-U. FIG. 11(c) illustrates
an example in which the vectors of phase-U and phase-Z are
25 in opposite directions, that is, the vector of phase-Z is
180 degrees out of phase with that of phase-U.
[0046] The group of phases U, V, and W and the group of
phases X, Y, and Z rotating in the opposite direction to
that of phases U,V,W provide three patterns, as in parts
30 (a) to (c) above. These patters are illustrated in the
bottom portion in the order of parts (d), (e), and (f) from
the left.
[0047] Any one of the above patterns of parts (a) to (f)
17
shows that the three phase pairs, each of which is a
combination of one phase of phases U, V, and W and a
corresponding one phase of phases X, Y, and Z, each have an
opposite phase relationship.
5 [0048] FIG. 12 is a diagram illustrating PWM control
signals generated by the individual phase voltage commands
illustrated in FIG. 11(a). FIG. 13 is a diagram of an
equivalent circuit of the circuit of FIG. 1, for use in
describing a leakage current in the first embodiment.
10 [0049] In FIG. 12, the first PWM control signals are PWM
control signals provided to the first inverter 121 that
controls the first motor group 161. The second PWM control
signals are PWM control signals provided to the second
inverter 122 that controls the second motor group 162.
15 [0050] An equivalent circuit of the circuit of FIG. 1 is
illustrated in FIG. 13. A phase-U voltage 33U, a phase-V
voltage 33V, and a phase-W voltage 33W are applied to the
induction motor 181 belonging to the first motor group 161.
As a neutral point potential 321 of the induction motor 181
20 varies, a leakage current 351 flows between the point at
the neutral point potential 321 and the line at the
reference potential 31 through a stray capacitor 341.
[0051] In addition, a phase-X voltage 33X, a phase-Y
voltage 33Y, and a phase-Z voltage 33Z are applied to the
25 induction motor 183 belonging to the second motor group 162.
As a neutral point potential 323 of the induction motor 183
varies, a leakage current 352 flows between the point at
the neutral point potential 323 and the line at the
reference potential 31 through a stray capacitor 343.
30 [0052] In FIG. 12, one of the waveform of the PWM
control signal for phase U and the waveform of the PWM
control signal for phase X is a vertically inverted
waveform of the other waveform. The same is true of the
18
relationship between the PWM control signal for phase V and
the PWM control signal for phase Y, and between the PWM
control signal for phase W and the PWM control signal for
phase Z. That is, the individual phases in the first PWM
5 control signals correspond one-to-one to the individual
phases in the second PWM modulation control signals, and a
pair of the PWM control signals has signal waveforms in
opposite phases to each other.
[0053] Thus, the common mode voltage generated at the
10 neutral point potential 321 of the induction motor 181 and
the common mode voltage generated at the neutral point
potential 323 of the induction motor 183 provide vertically
inverted pulse waveforms. As a result, the leakage current
351 flowing through the stray capacitor 341 and the leakage
15 current 352 flowing through the stray capacitor 343 are in
opposite phases to each other. In addition, the leakage
current 351 flowing through the first conductor 141 and the
leakage current 352 flowing through the second conductor
142 are in opposite phases to each other. More
20 specifically, leakage currents flow in opposite directions
in each of pairs of phase U and phase X, of phase V and
phase Y, and of phase W and phase Z. Magnetic fields
generated by leakage currents are thus canceled out in the
section where the electrical wirings for the corresponding
25 phases of each group are installed close to each other.
This results in reduction in a voltage induced in a wayside
device on the ground.
[0054] Note that FIG. 13 illustrates the pair of closely
arranged conductors for phase U and phase X, the pair of
30 closely arranged conductors for phase V and phase Y, and
the pair of closely arranged conductors for phase W and
phase Z. The arrangement of the conductors as illustrated
in FIG. 13 is advantageous in cancelling out the magnetic
19
fields generated by the leakage currents. A method of
installing a pair of conductors close to each other may be
to twist together a pair of conductors of corresponding
phases and install the twisted conductors. Note that all
5 the six conductors may be twisted together if the
production is feasible.
[0055] FIG. 14 is diagram for use in describing an
inter-conductor distance in the first embodiment. FIG. 14
illustrates the cross-sectional shapes of two conductors
10 501 and 502. In FIG. 14, the conductor 501 is, for example,
the conductor for phase U, and the conductor 502 is, for
example, the conductor for phase X.
[0056] Each of the conductors 501 and 502 includes a
conductor portion 52 and a sheath 54 that is an electrical
15 insulator covering the outer surface of the conductor
portion 52. The conductors 501 and 502 each have a
circular cross section. The inter-conductor distance
between the conductor 501 and the conductor 502 is herein
defined as the distance between the cross-sectional center
20 of the conductor 501 and the cross-sectional center of the
conductor 502. This distance is referred to as intercenter distance, which is denoted by “d”. As to how small
the foregoing inter-conductor distance should be, the first
embodiment is based on the assumption that the relationship
25 of Expression (1) below is satisfied, where a diameter “a”
of the conductor portion 52 is the reference length.
[0057] d≤3a … (1)
[0058] That is, in the first embodiment, the intercenter distance between the conductor 501 and the conductor
30 502 is equal to or less than three times the diameter “a”
of the conductor portion 52.
[0059] Note that although the conductors 501 and 502
illustrated in FIG. 14 each have a circular cross section,
20
the shape thereof is not limited thereto. That is, each
cross section may be non-circular. A non-circular shape
may be a shape other than a circle, such as a polygon such
as a triangle or a quadrangle, an elliptic shape, or a
5 shape defined by multiple curves.
[0060] In addition, although the conductor portions 52
of the conductors 501 and 502 illustrated in FIG. 14 have
the same diameter “a”, the conductor portions 52 may have
different diameters. Note that when the cross-sectional
10 shapes of the conductors 501 and 502 are not circular, and
differ from each other, Expression (1) above is modified as
follows.
[0061] First, the inter-center distance between the
conductor 501 and the conductor 502 is referred to as
15 “first length”, which is denoted by “b”. Then, the maximum
length of the conductor portion in the cross section of the
conductor 501 is referred to as “second length”, which is
denoted by “c1”. In addition, the maximum length of the
conductor portion in the cross section of the conductor 502
20 is referred to as “third length”, which is denoted by “c2”.
With “b”, “c1”, and “c2”, Expression (1) above can be
modified as shown by Expression (2) below.
[0062] b≤(c1/2+c2/2)×3 … (2)
[0063] That is, in the first embodiment, the first
25 length, i.e., the inter-center distance between the
conductor 501 and the conductor 502, is equal to or less
than three times the average value of the second length and
the third length, where the second length is the maximum
length of the conductor portion in the cross section of the
30 conductor 501, and the third length is the maximum length
of the conductor portion in the cross section of the
conductor 502.
[0064] Next, a description will be made as to some
21
considerations to take in providing the electric vehicle
control device according to the first embodiment.
[0065] FIG. 15 is a diagram illustrating a circuit
configuration of an electric vehicle control device
5 according to a comparative example for the circuit
configuration of FIG. 1. In FIG. 15, like reference
characters designate elements corresponding to elements
illustrated in FIG. 1.
[0066] In FIG. 15, a capacitor 111 and a filter reactor
10 761 are connected to a DC-side portion of the first
inverter 121. The capacitor 111 and the filter reactor 761
jointly form a first filter circuit. Similarly, a
capacitor 112 and a filter reactor 762 are connected to a
DC-side portion of the second inverter 122. The capacitor
15 112 and the filter reactor 762 jointly form a second filter
circuit. That is, FIG. 15 illustrates a configuration in
which the first inverter 121 and the second inverter 122
have filter circuits, separately.
[0067] As described above, in the electric vehicle
20 control device of the first embodiment, the first inverter
121 and the second inverter 122 perform switching operation
in opposite phases to each other. As a result, current
ripples generated in DC-side portions of the individual
inverters are in opposite phases. For the separate filter
25 circuits, thus, the capacitor voltages of the respective
inverters will differ between the first motor group 161 and
the second motor group 162. This will break symmetry of
the leakage currents generated in the groups.
[0068] In contrast, the configuration of FIG. 1 uses a
30 common capacitor, and a DC-side portion of the first
inverter 121 and a DC-side portion of the second inverter
122 are connected to the common capacitor in parallel.
This configuration allows the common capacitor to remove
22
current ripples that are in opposite phases to each other
and generated into DC-side portions of the individual
inverters. This maintains symmetry of the leakage currents
generated in the individual groups.
5 [0069] FIG. 16 is a diagram illustrating an example
arrangement of the induction motors, different from the
arrangement of FIG. 10, in the first embodiment. In FIG.
16, like reference characters designate elements
corresponding to elements illustrated in FIG. 10.
10 [0070] For a reason of underfloor space, or in view of
weight balance of each vehicle, inverters and motors may be
mounted on different vehicles in railroad vehicles. In
this case, as illustrated in FIG. 16, the induction motors
181 to 184 are mounted on a vehicle 401, and the first
15 inverter 121 and the second inverter 122 are mounted on a
vehicle 402. Bridge wiring 60, which is an inter-vehicle
electrical wiring, is provided between the vehicle 401 and
the vehicle 402.
[0071] The structure of the bridge wiring needs to be
20 flexibly deformable in view of the vehicle travelling in a
curved section and the vehicle vibration. Accordingly, the
bridge wiring is installed with some downward slack. The
bridge wiring would be thus more likely to have undesirable
effects on a wayside device as a distance between the
25 bridge wiring and a wayside device is shorter than between
wiring of the other portions and the wayside device. This
problem can be addressed employing the foregoing technique
of the first embodiment that enables the leakage currents
in the individual groups to be in opposite phases in the
30 bridge wiring 60 as well. This can cancel out the magnetic
fields in the bridge wiring 60 as well, thereby reducing a
voltage induced in a wayside device.
[0072] FIG. 17 is a diagram illustrating an example
23
configuration of a cooling device in the first embodiment.
FIG. 17 illustrates an example in which the six
semiconductor devices included in the first inverter 121
and the six semiconductor devices included in the second
5 inverter 122, i.e., the twelve semiconductor devices in
total, are mounted on a fin base 82 of a cooling device 80.
[0073] When the foregoing technique of the first
embodiment is used, it is more desirable that the
electrical wirings of the individual groups be installed in
10 parallel in a longer section. In addition, as described
above, the first inverter 121 and the second inverter 122
are preferably connected to a common capacitor. This
facilitates the first inverter 121 and the second inverter
122 sharing the cooling device with a reduced distance
15 between the first inverter 121 and the second inverter 122.
This enables downsizing the inverter unit including the
first inverter 121 and the second inverter 122.
[0074] For the electric vehicle control device according
to the first embodiment, as describe above, a first
20 inverter and induction motors belonging to a first motor
group are connected to each other by a first conductor, and
a second inverter and induction motors belonging to a
second motor group are connected to each other by a second
conductor. Between each of the first and second inverters
25 and the bogies having the induction motors mounted thereon,
a first length is equal to or less than three times the
average value of a second length and a third length, the
first length being the inter-center distance between the
first and second conductors, the second length being the
30 maximum length of a conductor portion of the first
conductor in the cross section of the first conductor, the
third length being the maximum length of a conductor
portion of the second conductor in the cross section of the
24
second conductor. This configuration cancels out magnetic
fields generated by leakage currents, thereby reducing a
voltage induced in a wayside device on the ground. This
can also reduce or eliminate leakage noise without relying
5 on additional installation of filter elements.
[0075] Note that, in the foregoing configuration, the
first inverter and the second inverter may be housed in the
same enclosure. This enables downsizing the device. In
addition, a variation in impedance between the leakage
10 current paths can be reduced. Moreover, the length of the
section where the wiring of each group is installed alone
can be reduced.
[0076] Also in the foregoing configuration, a single
capacitor for smoothing the DC voltage is provided, and a
15 DC-side portion of the first inverter and a DC-side portion
of the second inverter are both connected to the single
capacitor in parallel. This improves symmetry of output
voltages in the first motor group and the second motor
group, thereby improving the effect of canceling magnetic
20 fields generated by leakage currents.
[0077] Also in the foregoing configuration, the first
and second conductors may be twisted together, and
installed, between the first or second inverter and the
bogies. Installation of the first and second conductors
25 twisted together can reduce the distance between the first
conductor and the second conductor, thereby improving the
effect of canceling magnetic fields.
[0078] Note that when one of the first inverter 121 and
the second inverter 122 stops operating, the other inverter
30 preferably stops operating, too. Such control can prevent
generation of excess leakage noise.
[0079] Second Embodiment.
FIG. 18 is a diagram illustrating an in-vehicle
25
configuration of an electric vehicle control device
according to a second embodiment. In FIG. 18, like
reference characters designate elements corresponding to
elements illustrated in FIG. 10.
5 [0080] If the pulse-shaped voltage applied from each
inverter to corresponding motors is an ideal pulse-shaped
voltage that has a zero rise time or a zero fall time, the
common mode voltages in the respective groups will be
completely symmetric with respect to each other. Moreover,
10 if the impedances of the respective leakage current paths
are the same, the magnetic fields will be completely
canceled out. In fact, however, the rise time and the fall
time of a voltage waveform are not the same, because of a
delay time of a gate drive circuit or a variation in
15 characteristic among semiconductor devices. The impedances
of the leakage current paths are not the same, either.
[0081] In view of this, in the second embodiment, the
first conductor 141 and the second conductor 142, which are
wirings of the individual groups, are surrounded by the
20 same duct 70 as illustrated in FIG. 18. In the second
embodiment, the duct 70 is used as a shielding member.
[0082] Surrounding the wirings of the individual groups
with the same duct 70 can shield magnetic fields that
remain without being canceled out. In addition, capability
25 of shielding a very low level of magnetic field component
affecting the surrounding environment can reduce the effect
on a wayside device. Note that surrounding the wirings
with the same duct also provides an effect of preventing a
variation in impedance between the leakage current paths of
30 the individual groups. Note also that, needless to say,
the number of components is smaller than when a duct is
individually installed for the wiring of each group.
[0083] Meanwhile, FIG. 19 is a diagram illustrating an
26
in-vehicle configuration of an electric vehicle control
device according to a variation of the second embodiment.
In FIG. 19, like reference characters designate elements
corresponding to elements illustrated in FIG. 16.
5 [0084] Since no duct can be installed in the section of
the bridge wiring, ducts are installed in other sections
where the wirings run in parallel than the section of the
bridge wiring. FIG. 19 illustrates an example in which a
duct 701 is installed in the vehicle 401, and a duct 702 is
10 installed in the vehicle 402 other than the section of the
bridge wiring 60. Note that, from a viewpoint of reducing
a variation in leakage impedance, the wirings of the
individual groups are desirably contained in the duct in
sections of the same length. In other words, a smaller
15 difference between the wiring lengths of the portions of
the wirings of the individual groups contained in the duct
is more desirable.
[0085] As described above, in the electric vehicle
control device according to the second embodiment, the
20 first and second conductors are surrounded with the same
shielding member between the first or the second inverter
and the bogies. This configuration allows the shielding
member to shield the magnetic fields that has not been
canceled out, thereby reducing the effect on a wayside
25 device. In addition, a variation in impedance between the
leakage current paths of the individual groups can be
reduced.
[0086] Third Embodiment.
FIG. 20 is a diagram illustrating a configuration of
30 and around a bogie of an electric vehicle control device
according to a third embodiment. In FIG. 20, like
reference characters designate elements corresponding to
elements illustrated in FIG. 10.
27
[0087] FIG. 20 is a diagram of the first bogie 241
illustrated in FIG. 10 viewed from the rails. FIG. 20
illustrates wheels 57, axles 56 each interconnecting a pair
of the wheels 57, the first bogie 241 supported by the
5 axles 56, and the two induction motors 181 and 183 mounted
on the first bogie 241. The two induction motors 181 and
183 are each illustrated with a motor connection unit 58
that is an electrical connection unit for electrical
connection to the first conductor 141 or the second
10 conductor 142. The following description may designate the
motor connection unit 58 on each of the induction motors
belonging to the first motor group 161 as “first motor
connection unit”, and the motor connection unit 58 on each
of the induction motors belonging to the second motor group
15 162 as “second motor connection unit”.
[0088] Near the motor connection units 58 of the two
induction motors 181 and 183, there is a section where the
first conductor 141 and the second conductor 142 cannot be
installed in parallel. In the third embodiment, the length
20 of the section where the wirings of the individual groups
are not parallel is minimized as much as possible.
Specifically, the wirings of the individual groups are
routed along a middle position L, between the motor
connection unit 58 of the induction motor 181 and the motor
25 connection unit 58 of the induction motor 183 in the
vehicular travelling direction, and are then separated from
each other at the middle position L such that each of the
thus separated wirings is connected to the corresponding
one of the motor connection units 58. This configuration
30 provides an increased length of the section where the first
conductor 141 and the second conductor 142 run in parallel,
thereby reducing the residual magnetic field components
that have not been canceled out. This results in reduction
28
in the effect of leakage current on a wayside device near
the motor connection unit 58 as well.
[0089] Fourth Embodiment.
FIG. 21 is a diagram illustrating a configuration of
5 an inverter connection unit of an electric vehicle control
device according to a fourth embodiment. An inverter
connection unit 64 includes a first terminal portion 661
for connecting the first conductor 141 to the first
inverter 121, and a second terminal portion 662 for
10 connecting the second conductor 142 to the second inverter
122. The first terminal portion 661 includes three
terminals U, V, and W, and the second terminal portion 662
includes three terminals X, Y, and Z. Note that the
inverter connection unit 64 may be formed on any surface of
15 the enclosure 6 housing the first inverter 121 and the
second inverter 122.
[0090] In FIG. 21, the inverter connection unit 64 has a
transversely long, rectangular shape. The terminals U, V,
and W in the first terminal portion 661 are equidistantly
20 arranged along the longitudinal direction near a first side
68 of the two long sides of the inverter connection unit 64.
In addition, the terminals X, Y, and Z in the second
terminal portion 662 are equidistantly arranged along the
longitudinal direction near a second side 69 of the two
25 long sides of the inverter connection unit 64. Note that
although FIG. 21 illustrates the terminal X as being
positioned at a longitudinally offset position with respect
to the terminal U, the terminal X and the terminal U may be
longitudinally aligned with each other. This relationship
30 is also applicable to the terminal Y and the terminal V,
and to the terminal Z and the terminal W.
[0091] Meanwhile, as illustrated in FIG. 21, assume that
the center distance between the terminal U and the terminal
29
V is denoted by d1. Although not illustrated, the center
distance between the terminal V and the terminal W is d1,
and the center distance between the terminal U and the
terminal W is 2d1. Similarly, although not illustrated,
5 the center distance between the terminal X and the terminal
Y is d1, the center distance between the terminal Y and the
terminal Z is d1, and the center distance between the
terminal X and the terminal Z is 2d1. The distance d1 is
therefore the minimum distance between phase terminals of
10 the first terminal portion 661, and is also the minimum
distance between phase terminals of the second terminal
portion 662.
[0092] In addition, as illustrated in FIG. 21, assume
that the center distance between the terminal U and the
15 terminal X is denote by d2. Although not illustrated, the
center distance between the terminal V and the terminal Y,
and the center distance between the terminal W and the
terminal Z are also d2. Note that the center distance
between the terminal U and the terminal Y, and the center
20 distance between the terminal U and the terminal Z are
longer than d2. The center distance between the terminal X
and the terminal V, and the center distance between the
terminal X and the terminal W are also longer than d2. The
distance d2 is therefore the minimum distance between the
25 first terminal portion 661 and the second terminal portion
662.
[0093] These distances d1 and d2 satisfy the
relationship of Expression (3) below.
[0094] d2≤d1 … (3)
30 [0095] Radiation noise generated in the enclosure 6 is
shielded and prevented from leaking out. Meanwhile, a
magnetic field generated by leakage current may have an
effect on a wayside device at near the inverter connection
30
unit 64 to which the conductors are connected. Thus, in
the fourth embodiment, the terminals are arranged, as
expressed by Expression (3) above, such that the intercenter distance between the terminals of phases providing
5 the PWM control signals in opposite phases is equal to or
less than the inter-center distance between the terminals
of phases of the same group. In other words, the terminals
are arranged such that the minimum distance between the
first terminal portion 661 and the second terminal portion
10 662 is equal to or less than the minimum distance between
phase terminals in the first terminal portion 661 or the
minimum distance between phase terminals in the second
terminal portion 662. Such a configuration can reduce
radiation noise emitted from or from near the enclosure 6
15 housing the first inverter 121 and the second inverter 122.
[0096] The functionality of the control unit 20 in the
first embodiment through the fourth embodiment described
above can be implemented in a hardware configuration
illustrated in FIG. 22 or 23. FIG. 22 is a block diagram
20 illustrating an example of hardware configuration that
implements the functionality of the control unit in the
first embodiment through the fourth embodiment. FIG. 23 is
a block diagram illustrating another example of hardware
configuration that implements the functionality of the
25 control unit in the first embodiment through the fourth
embodiment.
[0097] The functionality of the control unit 20 in the
first embodiment can be implemented, as illustrated in FIG.
22, in a configuration including a processor 300, which
30 performs computation, a memory 302, which stores a program
to be read by the processor 300, and an interface 304,
which inputs and outputs a signal.
[0098] The processor 300 may be computing means such as
31
a computing unit, a microprocessor, a microcomputer, a
central processing unit (CPU), or a digital signal
processor (DSP). In addition, the memory 302 may be a nonvolatile or volatile semiconductor memory such as a random
5 access memory (RAM), a read-only memory (ROM), a flash
memory, an erasable programmable ROM (EPROM), or an
electrically EPROM (EEPROM) (registered trademark); a
magnetic disk, a flexible disk, an optical disk, a compact
disc, a MiniDisc, or a digital versatile disc (DVD).
10 [0099] The memory 302 stores a program for implementing
the functionality of the control unit 20 in the first
embodiment through the fourth embodiment. The processor
300 provides and receives necessary information via the
interface 304, and executes a program stored in the memory
15 302, and can thus perform processing described above. The
result of computation by the processor 300 can be stored in
the memory 302.
[0100] Alternatively, the functionality of the control
unit 20 in the first embodiment through the fourth
20 embodiment can also be implemented by using processing
circuitry 305 illustrated in FIG. 23.
[0101] In FIG. 23, the processing circuitry 305 may be a
single circuit, a set of multiple circuits, an application
specific integrated circuit (ASIC), a field-programmable
25 gate array (FPGA), or a combination thereof. The
processing circuitry 305 can obtain information input to
the processing circuitry 305 and information output from
the processing circuitry 305 via an interface 306.
[0102] Note that the configurations described in the
30 foregoing embodiments are merely examples of various
aspects of the present invention. These configurations may
be combined with a known other technology, and moreover, a
part of such configurations may be omitted and/or modified
32
without departing from the spirit of the present invention.
Reference Signs List
[0103] 1 overhead line; 2 current collector unit; 3,
5 57 wheel; 4 rail; 5 reactor; 6 enclosure; 10 electric
vehicle control device; 11, 111, 112 capacitor; 12
inverter; 121 first inverter; 122 second inverter; 141
first conductor; 142 second conductor; 161 first motor
group; 162 second motor group; 18, 181, 182, 183, 184
10 induction motor; 20 control unit; 22U phase-U leg; 22V
phase-V leg; 22W phase-W leg; 22X phase-X leg; 22Y
phase-Y leg; 22Z phase-Z leg; 24 bogie; 241 first bogie;
242 second bogie; 26U phase-U voltage command; 26V
phase-V voltage command; 26W phase-W voltage command; 28
15 carrier; 31 reference potential; 32, 321, 323 neutral
point potential; 33U phase-U voltage; 33V phase-V
voltage; 33W phase-W voltage; 33X phase-X voltage; 33Y
phase-Y voltage; 33Z phase-Z voltage; 34, 341, 343 stray
capacitor; 35, 351, 352 leakage current; 40, 401, 402
20 vehicle; 501, 502 conductor; 52 conductor portion; 54
sheath; 56 axle; 58 motor connection unit; 60 bridge
wiring; 64 inverter connection unit; 661 first terminal
portion; 662 second terminal portion; 68 first side; 69
second side; 70, 701, 702 duct; 761, 762 filter reactor;
25 80 cooling device; 82 fin base; UNI, VNI, WNI, UPI, VPI,
WPI semiconductor device.

We Claim :
1. An electric vehicle control device to control a
plurality of induction motors with a single inverter, the
electric vehicle control device comprising:
5 a first inverter to control a first electric motor
group defined by a plurality of induction motors; and
a second inverter to control a second electric motor
group defined by a plurality of induction motors, wherein
the induction motors belonging to the first electric
10 motor group are mounted on different bogies,
the induction motors belonging to the second electric
motor group are mounted on different bogies,
the first inverter and the induction motors belonging
to the first electric motor group are connected to each
15 other by a first conductor,
the second inverter and the induction motors belonging
to the second electric motor group are connected to each
other by a second conductor, and
between each of the first and second inverters and the
20 bogies, a first length is equal to or less than three times
an average value of a second length and a third length, the
first length being an inter-center distance between the
first conductor and the second conductor, the second length
being a maximum length of a conductor portion of the first
25 conductor in a cross section of the first conductor, the
third length being a maximum length of a conductor portion
of the second conductor in a cross section of the second
conductor.
30 2. The electric vehicle control device according to claim
1, comprising:
a control unit to output first pulse width modulation
control signals to the first inverter, and to output second
34
pulse width modulation control signals to the second
inverter, wherein
individual phases in the first pulse width modulation
control signals correspond in one-to-one to individual
5 phases in the second pulse width modulation control signals,
and a pair of the first and second pulse width modulation
control signals have signal waveforms in opposite phases to
each other.
10 3. The electric vehicle control device according to claim
1 or 2, wherein
the first and second conductors are surrounded with
the same shielding member between the first or second
inverter and the bogies.
15
4. The electric vehicle control device according to any
one of claims 1 to 3, wherein
the first and second conductors are twisted together,
and installed, between the first or second inverter and the
20 bogies.
5. The electric vehicle control device according to any
one of claims 1 to 4, wherein
the induction motors belonging to the first electric
25 motor group each include a first motor connection unit to
be connected to the first conductor,
the induction motors belonging to the second electric
motor group each include a second motor connection unit to
be connected to the second conductor, and
30 the first conductor and the second conductor are
installed such that the first conductor and the second
conductor are routed along a middle position between the
first motor connection unit and the second motor connection
35
unit.
6. The electric vehicle control device according to any
one of claims 1 to 5, wherein
5 the first and second inverters are housed in the same
enclosure.
7. The electric vehicle control device according to claim
6, wherein
10 the enclosure comprises
a first terminal portion to be connected to the
first conductor, and
a second terminal portion to be connected to the
second conductor, and
15 a minimum distance between the first terminal portion
and the second terminal portion is equal to or less than a
minimum distance between phase terminals in the first
terminal portion or a distance between phase terminals in
the second terminal portion.
20
8. The electric vehicle control device according to claim
6 or 7, wherein
the enclosure comprises a single capacitor to smooth a
direct current voltage, and
25 a direct current-side portion of the first inverter
and a direct current-side portion of the second inverter
are both connected to the capacitor in parallel.
9. The electric vehicle control device according to any
30 one of claims 6 to 8, wherein
a plurality of semiconductor devices included in the
first inverter and a plurality of semiconductor devices
included in the second inverter comprises are mounted on
36
the same cooling device for cooling the semiconductor
devices included in the first and second inverters.
10. The electric vehicle control device according to any
5 one of claims 1 to 9, wherein
when one of the first and second inverters stops
operating, the other inverter stops operating.