1. A power converter frame that houses a power converter, the power converter frame comprising at least: a base frame and a top frame each of which is formed by a plurality of beams that are disposed in a polygonal shape and are coupled to each other; a plurality of struts that are provided on the base frame to couple the base frame and the top frame to each other, and that support the top frame; and a shelf that is provided at a position between the base frame and the top frame and is supported by the struts, wherein at least one of the beam, the strut, and the shelf, positioned near a position at which a DC power main circuit of the power converter is disposed, is formed of a nonmagnetic member with low resistivity, and at least one of the beam, the strut, and the shelf, positioned near a position at which an AC power main circuit of the power converter is disposed, is formed of a nonmagnetic member with high mechanical strength.

2. The power converter frame according to claim 1, wherein the nonmagnetic member with low resistivity is copper, and the nonmagnetic member with high mechanical strength is stainless steel.

3. The power converter frame according to claim 2, wherein 22 the beam, the strut, and the shelf are not positioned near a position at which the DC power main circuit of the power converter is disposed and near a position at which the AC power main circuit of the power converter is disposed, in the beams, the struts, and the shelf, are formed of steel.

4. The power converter frame according to claim 2, wherein the power converter and the AC power main circuit are disposed on the shelf, and the shelf is formed of stainless steel.

5. A power converter configured to be housed in the power converter frame according to claim 1.

BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001]
The present invention relates to a power converter frame
suitable for particularly housing a large-capacity power
converter, and a power converter housed in the power converter
frame.
2. Description of the Related Art
[0002]
JP-H5-300630-A discloses an example of structure of a
frame for housing enclosed bus bars. Conventionally, a frame
for housing enclosed bus bars has a problem in which eddy-current
causes the frame to generate heat while the bus bars are
energized. JP-H5-300630-A shows that the entire frame is
formed of nonmagnetic material such as aluminum and stainless
steel, or a slit is provided in the frame in a direction parallel
to the bus bars and the slit is filled with nonmagnetic material,
to reduce heat generation caused by eddy-current.
[0003]
In addition, JP-2009-171761-A describes an example of
a switchboard in which large-current bus bars are laid near a
board frame formed of steel, board frame and a magnetism shield
3
member formed of an electromagnetic steel plate with high
permeability and high resistance is laid along the board frame.
The board frame described above enables eddy-current to be
reduced by the magnetism shield member to reduce heat generation
caused by the eddy-current.
[0004]
SUMMARY OF THE INVENTION
[0005]
Usually, nonmagnetic stainless steel and nonmagnetic
steel are used as a material of a conventional typical
large-capacity power converter frame. However, in a case where
electric current including many high frequency components
causes linkage, stainless steel and steel cause their reduction
effect of heat generation caused by eddy-current to be reduced
as described latter. Thus, a large-capacity power converter
frame, as described above, requires measures such as disposing
a main circuit of the large-capacity power converter at a place
away from a frame. As a result, the frame increases in size.
[0006]
In addition, since the large-capacity power converter
frame houses a large-capacity power converter being a heavy
object, forming a slit in a beam and a strut of the frame is
not acceptable from viewpoints of mechanical strength and shock
resistance of the frame. Further, laying a magnetism shield
4
member also causes the frame to increase in size and causes high
cost.
[0007]
In light of the problem of a conventional art described
above, it is an object of the present invention to provide a
power converter frame and a power converter housed in the power
converter frame, the power converter frame being capable of
reducing its heat generation caused by eddy-current without
increasing in size as well as deteriorating in mechanical
strength and shock resistance.
[0008]
A power converter frame according to the present
invention houses a power converter, and includes at least: a
base frame and a top frame each of which is formed of a plurality
of beams that are disposed in a polygonal shape and are coupled
to each other; a plurality of struts that are provided on the
base frame to couple the base frame and the top frame to each
other, and that support the top frame; and a shelf that is
provided at a position between the base frame and the top frame
and is supported by the struts. At least one of the beam, the
strut, and the shelf, positioned near a position at which a DC
power main circuit of the power converter is disposed, is formed
of a nonmagnetic member with low resistivity, and at least one
of the beam, the strut, and the shelf, positioned near a position
at which an AC power main circuit of the power converter is
5
disposed, is formed of a nonmagnetic member with high mechanical
strength.
[0009]
According to the present invention, there is provided
a power converter frame and a power converter housed in the power
converter frame, the power converter frame being capable of
reducing its heat generation caused by eddy-current without
increasing in size as well as deteriorating in mechanical
strength and shock resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
Fig. 1 illustrates an example of a circuit configuration
of a power converter according to an embodiment of the present
invention;
Fig. 2 is a front view of an example of an appearance
of a power converter frame according to the embodiment of the
present invention;
Fig. 3 illustrates an example of framework structure of
the power converter frame according to the embodiment of the
present invention;
Fig. 4 illustrates an example of frequency
characteristics of steel, stainless steel, and copper, with
respect to heating by eddy-current;
6
Fig. 5 illustrates an example of schematic placement of
main circuit copper strips in the power converter frame
according to the embodiment of the present invention; and
Fig. 6 illustrates an example of schematic placement of
main circuit copper strips and placement of semiconductor
switching units, in the power converter frame according to the
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011]
Preferred embodiments of the present invention will be
described in detail below with reference to accompanying
drawings.
[0012]
Fig. 1 illustrates an example of a circuit configuration
of a power converter 1 according to an embodiment of the present
invention. The power converter 1 converts AC power into DC
power, or DC power into AC power. While the circuit
configuration of the power converter 1 of Fig. 1 is similar to
that of a conventional typical power converter, the power
converter 1 of the present embodiment is configured to convert
particularly large power.
[0013]
In Fig. 1, a power converter 1c configured to convert
AC power into DC power is called a converter, and a power
7
converter 1i configured to convert DC power into AC power is
called an inverter. In addition, a device having both the power
converter 1c being a converter and the power converter 1i being
an inverter is often called a power converter. While the power
converter 1 of the present embodiment may be any one to them,
the power converter 1 is any one of the power converter 1c being
a converter and the power converter 1i being an inverter in the
description of Fig. 1 and subsequent drawings.
[0014]
As illustrated in Fig. 1, the power converters 1c and
1i each include three semiconductor switching circuits 10, 11,
and 12. These three semiconductor switching circuits 10, 11,
and 12 each are connected to a positive side DC wiring 7p and
a negative side DC wiring 7n, as well as to an AC power source
2 or a motor 3 through AC wirings 6c and 6i having U-phase,
V-phase, and W-phase, or R-phase, S-phase, and T-phase.
[0015]
The semiconductor switching circuits 10, 11, and 12 each
include two switching elements 4p and 4n that are connected in
series between the positive side DC wiring 7p and the negative
side DC wiring 7n. In Fig. 1, while an insulating gate bipolar
transistor (IGBT) is used for each of the switching elements
4p and 4n, a switching element other than the IGBT may be used.
In a case where the switching elements 4p and 4n each are the
IGBT, the corresponding one of diodes 5p and 5n in a reverse
8
direction is connected between an emitter and a collector each
of the switching elements 4p and 4n.
[0016]
In addition, each of the AC wirings 6c and 6i having
U-phase, V-phase, and W-phase, or R-phase, S-phase, and T-phase,
from the AC power source 2 or the motor 3, is connected to
respective nodes to which the upper and lower two switching
elements 4p and 4n constituting each of the semiconductor
switching circuit 10, 11, and 12 are connected. A control signal
(gate input signal of the IGBT) controlling the switching
elements 4p and 4n (IGBT) to be switched is supplied from a
control device (not illustrated).
[0017]
In the power converter 1 (1c and 1i) as described above,
each of the AC wirings 6c and 6i connected to the AC power source
2 or the motor 3 is often called an AC power main circuit 6,
and each of the positive side DC wiring 7p and the negative side
DC wiring 7n is called a DC power main circuit 7. At this time,
a frequency of electric current flowing through the AC power
main circuit 6 is mainly determined in conjunction with a
frequency of the AC power source 2, a rotation speed of the motor
3, and the like. Thus, there is a predominance of low frequency
components in frequency components of the electric current.
Meanwhile, electric current flowing through the DC power main
circuit 7 is controlled by a control signal in the shape of a
9
rectangle, controlling the switching elements 4p and 4n to be
switched. Thus, there is a predominance of high frequency
components in frequency components of the electric current
flowing through the DC power main circuit 7.
[0018]
Fig. 2 is a front view of an example of an appearance
of power converter frames 81 and 82 according to the embodiment
of the present invention. As illustrated in Fig. 2, each of
the power converter frames 81 and 82 is formed in the shape of
a box and has hinged double doors, for example. The power
converter frames 81 and 82 house semiconductor switching units
90 to 95 to which one of the AC wirings 6c and 6i having U-phase,
V-phase, and W-phase, or R-phase, S-phase, and T-phase, is
connected. Each of the semiconductor switching units 90 to 95
is a substantially rectangular unit packaging one of the
semiconductor switching circuits 10, 11, and 12 illustrated in
Fig. 1, each of which has a switching element 4 and a diode 5,
mounted on a board.
[0019]
That is, the power converter frame 81 for the power
converter 1c (converter) houses the semiconductor switching
units 90, 91, and 92 to which the AC wiring 6c with R-phase,
S-phase, and T-phase is connected. The power converter frame
82 for the power converter 1i (inverter) houses the
10
semiconductor switching units 93, 94, and 95 to which the AC
wiring 6i with U-phase, V-phase, and W-phase is connected.
[0020]
In the example of Fig. 2, each of the semiconductor
switching units 90 to 95 is disposed in an upper portion inside
the corresponding one of the power converter frame 81 and 82.
That is, since the semiconductor switching units 90 to 95 through
which large current flows to have a large heating value are
disposed in the corresponding upper portions inside the power
converter frames 81 and 82, the heat can be efficiently diffused
through a top portion (ceiling) of each of the power converter
frames 81 and 82. In addition, an exhaust heat device, such
as a fan, is provided in an upper portion outside the power
converter frames 81 and 82, and a vent hole and the like are
provided in the hinged double doors in a front face.
[0021]
In a lower portion inside the power converter frames 81
and 82, a control circuit configured to control each of the
semiconductor switching circuits 10, 11, and 12 is disposed.
[0022]
In a case where the semiconductor switching units 90 to
95 are disposed as described above, each of the positive side
DC wiring 7p and the negative side DC wiring 7n illustrated in
Fig. 1 is disposed at a position behind the semiconductor
switching units 90 to 95 (a back side in a paper-surface), the
11
position being illustrated by thick broken lines P and N. In
addition, each of the AC wiring 6c with R-phase, S-phase, and
T-phase, and the AC wiring 6i with U-phase, V-phase, and W-phase,
is disposed on a side of the corresponding one of the
semiconductor switching units 90 to 95, in a direction from a
front face side of the power converter frames 81 and 82 to a
rear side thereof (perpendicular to the paper-surface).
Placement of the DC power main circuit 7 and the AC power main
circuit 6 will be separately described in detail with reference
to Figs. 5 and 6.
[0023]
Fig. 3 illustrates an example of framework structure of
the power converter frame 81 according to the embodiment of the
present invention. Since each of the power converter frames
81 and 82 has the same framework structure, the framework
structure of only one of them (power converter frame 81) is
illustrated.
[0024]
As shown in Fig. 3, a basic framework of the power
converter frame 81 includes: a base frame formed of four beams
21 to 24 that are disposed in a quadrangular shape and are coupled
to each other; a top frame formed of four beams 26 to 29 that
are disposed in a quadrangular shape and are coupled to each
other; and four struts 31 that vertically couple four corners
of the base frame and the corresponding four corners of the top
12
frame. In this case, the four struts 31 are provided on the
corresponding four corners of the base frame (the beams 21 to
24) so as to be substantially perpendicular to a face of the
base frame, and support the top frame. As the beams 21 and 24,
the beams 26 to 29, and the strut 31, angle steel with an L-shaped
cross section and the like are used, for example.
[0025]
Each of the four beams 21 to 24 of the base frame and
the corresponding one of the four struts 31 are firmly coupled
to each other at the corresponding one of the four corners of
the base frame with a corner member 40. Likewise, each of the
four beams 26 to 29 of the top frame and the corresponding one
of the four struts 31 are firmly coupled to each other at the
corresponding one of the four corners of the top frame with a
corner member 45. The corner member 40 (45) has three planes
orthogonal to each other, and a notch is formed at each of
portions where the three planes intersect with each other. The
three planes are brought into contact with the corresponding
side faces of two of the beams and one of the struts, and are
firmly coupled to each other with a rivet, by welding, or the
like. This allows the power converter frame 81 to secure
mechanical strength and shock resistance.
[0026]
In addition, a shelf 43 is provided at an intermediate
height position between the base frame (the beams 21 to 24) and
13
the top frame (the beams 26 to 29) so that the semiconductor
switching units 90 to 92 are mounted thereon. At this time,
auxiliary struts 35 and 38 are provided at respective positions
between two of the struts 31 on the front face side and the
corresponding two of the struts 31 on the rear side, and the
shelf 43 is supported by the two of the struts 31 on the front
face side and the two auxiliary struts 35 and 38. Further, the
auxiliary struts 35 and 38 are respectively coupled to the beams
21 and 23 of the base frame, and the beams 26 and 28 of the top
frame, as well as are coupled to each other through auxiliary
beams 25 and 30.
[0027]
The shelf 43, for example, includes: two auxiliary beams
43a provided so as to couple the two struts 31 on the front face
side and the two auxiliary struts 35 and 38 to each other at
the intermediate height position between the base frame and the
top frame in a substantially horizontal manner; and a shelf plate
43b disposed between the two auxiliary beams 43a. It is
preferable that the shelf plate 43b is provided with vent holes
within a range without deteriorating its mechanical strength.
In consideration of mounting the semiconductor switching units
90 to 92 each of which is a heavy object on the shelf plate 43b,
auxiliary struts 36 and 37 are further provided at respective
intermediate positions of the two auxiliary beams 43a to support
14
the two auxiliary beams 43a at the respective intermediate
positions.
[0028]
There are provided beams 41 and 42 between the auxiliary
struts 35 and 38 at an intermediate height position between the
shelf 43 and the top frame (the beams 26 to 29) to couple the
auxiliary struts 35 and 38 to each other in a substantially
horizontal manner. The beams 41 are cantilever beams
protruding backward from the respective struts 35 and 38, and
the beams 42 each couple ends of the respective two cantilever
beams 41 to each other. The beams 41 and 42 are provided to
support wiring members (main circuit copper strips 56 in Fig.
5) of the DC power main circuit 7.
[0029]
Fig. 4 illustrates an example of frequency
characteristics of steel, stainless steel, and copper, with
respect to heating by eddy-current. The graph of Fig. 4 has
a horizontal axis representing a frequency of electric current
to be a cause of eddy-current, and a vertical axis representing
a temperature rise value of material to be heated by
eddy-current. In the present embodiment, electric current to
be a cause of eddy-current indicates electric current flowing
through the AC power main circuit 6 or the DC power main circuit
7.
[0030]
15
As illustrated in Fig. 4, there is no large difference
in a temperature rise value of material to be heated by
eddy-current among steel, stainless steel, and copper when a
frequency of electric current is low. However, while the copper
has a temperature rise value that increases little even if a
frequency increases, the steel and the stainless steel each have
a temperature rise value that significantly increases with
increase in frequency. Then, the steel increases in the value
more than the stainless steel.
[0031]
Fig. 5 illustrates an example of schematic placement of
main circuit copper strips 51, 54, and 56 in the power converter
frame 81 according to the embodiment of the present invention.
Fig. 6 illustrates schematic placement of the main circuit
copper strips 51, 54, and 56, and an example of placement of
the semiconductor switching units 90 to 92. Since the placement
of the main circuit copper strips 51, 54, and 56 in each of the
power converter frames 81 and 82 is similar, the placement in
the power converter frame 81 will be described.
[0032]
The semiconductor switching unit 90 to 92 each being a
main component of the power converter 1 are mounted on the shelf
43 and fixed, as illustrated in Fig. 6. Then, three main circuit
copper strips 54 corresponding to the AC power main circuit 6,
or respective wiring members of R-phase, S-phase, and T-phase
16
of the AC wiring 6c, are disposed on a side of the corresponding
one of the semiconductor switching units 90, 91, and 92. In
addition, two main circuit copper strips 56 corresponding to
the DC power main circuit 7, or respective wiring members of
the positive side DC wiring 7p and the negative side DC wiring
7n, are disposed behind the semiconductor switching units 90
to 92. The copper strip represents a conductor (wiring member)
for large current formed in the shape of an elongated plate or
a tape with a predetermined thickness.
[0033]
As described above, there is a feature in which electric
current flowing through the AC power main circuit 6 has a
predominance of low frequency components, and electric current
flowing through the DC power main circuit 7 has a predominance
of high frequency components. In the present embodiment, the
semiconductor switching units 90 to 92 each being a heavy object
are mounted on the shelf 43 as illustrated in Figs. 5 and 6.
Then, the main circuit copper strips 54 constituting the AC power
main circuit 6 are disposed above a top face of the shelf 43
through insulation so as to be substantially parallel to each
other.
[0034]
That is, since the main circuit copper strips 54 of the
AC power main circuit 6 are disposed near the shelf 43, electric
current flowing through the main circuit copper strips 54 causes
17
eddy-current in the shelf 43. However, since the electric
current flowing through the main circuit copper strips 54 has
a predominance of low frequency components, the shelf 43 is
formed of stainless steel with large mechanical strength in the
present embodiment.
[0035]
As illustrated in Figs. 5 and 6, the three main circuit
copper strips 54 extends toward the rear of the respective
semiconductor switching units 90, 91, and 92, and connected to
respective other three main circuit copper strips 51 provided
below the semiconductor switching units (in Fig. 5, copper
strips connecting the main circuit copper strips 54 and 51 are
not illustrated). Then, each of the main circuit copper strips
51 is connected to the AC power source 2 or the motor 3 through
a three-phase AC power cable or the like.
[0036]
Meanwhile, the main circuit copper strips 56 of the DC
power main circuit 7 are supported by the beams 41 and 42, and
are disposed near the beams 41 and 42. Thus, electric current
flowing through the DC power main circuit 7 causes eddy-current
in the beams 41 and 42. Since the electric current flowing
through the DC power main circuit 7 has a predominance of high
frequency components, the beams 41 and 42 is formed of copper
in the present embodiment.
[0037]
18
In the present embodiment, the beams 41 and 42 supporting
the main circuit copper strips 56 include the beams 41 protruding
backward from the respective struts 35 and 38, and the beams
42 coupling the ends of the respective beams 41 to each other,
as described above. That is, the main circuit copper strips
56 each are disposed at a position away from the shelf 43 and
the struts 35 and 38. Thus, even if the shelf 43 and the struts
35 and 38 are formed of stainless steel or steel, eddy-current
to be generated in them can be reduced in the present embodiment.
[0038]
As described above, the beam, the strut, and the shelf,
positioned near the DC power main circuit 7, in the beams, the
struts, and the shelf, constituting the power converter frame
81, are formed of copper in the present embodiment. In addition,
the beam, the strut, and the shelf, positioned near the AC power
main circuit 6 to be used as a strength member for supporting
a heavy object, are formed of nonmagnetic stainless steel with
large mechanical strength. Further, the beam, the strut, the
shelf, the corner member, and the like, other than the above,
are formed of steel with large mechanical strength.
[0039]
As described above, since the power converter frame 81
according to the present embodiment uses steel, stainless steel,
and copper according to their characteristics, heat generation
caused by eddy-current in the power converter frame 81 can be
19
reduced, and required mechanical strength and shock resistance
can be secured. In addition, the DC power main circuit 7 and
the AC power main circuit 6 can be disposed closer to the beams,
the struts, and the shelf, constituting the power converter
frame 81, as compared with a conventional frame, and thus the
power converter frame 81 can be reduced in size.
[0040]
While basic structure of the framework of the power
converter frame 81 and 82 described above includes: the base
frame formed of the four beams that are disposed in a
quadrangular shape and are coupled to each other; the top frame
formed of the four beams that are disposed in a similar shape
to that of the base frame and are coupled to each other; and
the four struts 31 that vertically couple both the base frame
and the top frame to each other, the base frame and the top frame
are not limited to the shape of a quadrangular. The base frame
and the top frame each may be formed of six or eight beams to
be formed in the shape of a hexagon or an octagonal.
[0041]
In the embodiment described above, while the circuit
configuration of the electric power conversion has two levels
(p and n), three levels may be available. In this case, the
DC power main circuit 7 includes a neutral point DC wiring in
addition to the positive side DC wiring 7p and the negative side
DC wiring 7n.
20
[0042]
In addition, while a three-phase AC is used as the AC
for electric power conversion in the embodiment described above,
a single-phase AC may be available. In that case, the power
converter frame 81 (82) houses two semiconductor switching units
90 and 91 (93 and 94) instead of three units.
[0043]
The present invention is not limited to the embodiment,
and includes various modifications. The embodiment above is
described in detail to easily understand the present invention,
and thus the present invention is not necessarily limited to
the embodiment provided with all structure described above. In
addition, a part of structure of an embodiment can be substituted
with a part of structure of another embodiment, and it is also
possible to add a part of or all of structure of an embodiment
to structure of another embodiment.

We claim:
1. A power converter frame that houses a power converter,
the power converter frame comprising at least:
a base frame and a top frame each of which is formed by
a plurality of beams that are disposed in a polygonal shape and
are coupled to each other;
a plurality of struts that are provided on the base frame
to couple the base frame and the top frame to each other, and
that support the top frame; and
a shelf that is provided at a position between the base
frame and the top frame and is supported by the struts,
wherein at least one of the beam, the strut, and the shelf,
positioned near a position at which a DC power main circuit of
the power converter is disposed, is formed of a nonmagnetic
member with low resistivity, and
at least one of the beam, the strut, and the shelf,
positioned near a position at which an AC power main circuit
of the power converter is disposed, is formed of a nonmagnetic
member with high mechanical strength.
2. The power converter frame according to claim 1, wherein
the nonmagnetic member with low resistivity is copper,
and the nonmagnetic member with high mechanical strength is
stainless steel.
3. The power converter frame according to claim 2, wherein
22
the beam, the strut, and the shelf are not positioned
near a position at which the DC power main circuit of the power
converter is disposed and near a position at which the AC power
main circuit of the power converter is disposed, in the beams,
the struts, and the shelf, are formed of steel.
4. The power converter frame according to claim 2, wherein
the power converter and the AC power main circuit are
disposed on the shelf, and the shelf is formed of stainless
steel.
5. A power converter configured to be housed in the power
converter frame according to claim 1.