Busbar, power module, and power conversion device

Abstract

Embodiments of the present invention provide a busbar of a power module, a power module, and a power conversion device having the power module. On the basis of the busbar, the power module, and the power conversion device provided by the embodiments of the present invention, a first busbar portion and a second busbar portion are both bent towards a first side of the busbar in the thickness direction relative to a third busbar portion, and thus can be bent towards a second heat sink and a third heat sink, respectively. In this way, the distance between the busbar and the second heat sink and the distance between the busbar and the third heat sink are further reduced, which helps to shorten the length of wire harnesses that electrically connects the busbar to a device set mounted on the second heat sink and a device set mounted on the third heat sink, thereby helping reduce stray inductance.

Description

Busbars, power modules and power conversion devices

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 202410956006.X, entitled "Power Module and Power Conversion Device", filed on July 17, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of power electronics technology, and in particular to a busbar suitable for a power module, a power module, and a power conversion device having the power module. Background Technology

[0004] Power conversion devices enable the conversion between direct current (DC) and alternating current (AC), and are widely used in power generation, transmission, and consumption applications. For example, power conversion devices can be used in electric vehicles, acting as a bridge between the battery system and the power grid / load.

[0005] Power modules are the core component of power conversion devices, typically consisting of busbars and groups of capacitors and devices electrically connected to them. Stray inductance in the power module circuitry can affect current balance, negatively impacting the performance of the power conversion device. Therefore, there is a need in this field to improve and reduce stray inductance. Summary of the Invention

[0006] In view of this, embodiments of the present invention provide a busbar suitable for a power module, a power module having the busbar, and a power conversion device having the power module, so as to at least improve the problem of high stray inductance in the power module circuit.

[0007] In one aspect, embodiments of the present invention provide a busbar. This busbar is applicable to power modules. The busbar includes a first busbar portion, a second busbar portion, and a third busbar portion. The third busbar portion is located between the first and second busbar portions in the width direction of the busbar. The first busbar portion is bent relative to the third busbar portion in a first side in the thickness direction of the busbar and is arranged at an angle to the third busbar. The second busbar portion is also bent relative to the third busbar portion in a first side in the thickness direction of the busbar and is arranged at an angle to the third busbar.

[0008] In some embodiments, the first busbar portion and the third busbar portion form an angle γ1, and the second busbar portion and the third busbar portion form an angle γ2. 100° ≤ γ1 ≤ 170°, and / or, 100° ≤ γ2 ≤ 170°.

[0009] In some embodiments, 120°≤γ1≤150°, and / or, 120°≤γ2≤150°

[0010] In some embodiments, γ1 = 135°, and / or γ2 = 135°.

[0011] In some embodiments, the busbar includes a stacked first electrode plate, a second electrode plate, and a third electrode plate. The second electrode plate is located between the first and third electrode plates. The first electrode plate is closer to a first side in the thickness direction of the busbar than the third electrode plate. In the first busbar portion, the first electrode plate is shorter than the second electrode plate. In the second busbar portion, the first electrode plate is shorter than the second electrode plate.

[0012] On the other hand, embodiments of the present invention also provide a power module. The power module includes multiple heat sinks, multiple device groups, and a busbar. The multiple heat sinks include a second heat sink and a third heat sink. A portion of the multiple device groups is mounted on the second heat sink, and another portion of the multiple device groups is mounted on the third heat sink. Both the second and third heat sinks are located on a first side in the thickness direction of the busbar. The busbar includes a first busbar portion, a second busbar portion, and a third busbar portion. The third busbar portion is located between the first and second busbar portions in the width direction of the busbar. The first busbar portion bends towards the second heat sink relative to the third busbar portion and is arranged at an angle to the third busbar. The second busbar portion bends towards the third heat sink relative to the third busbar portion and is arranged at an angle to the third busbar.

[0013] In some embodiments, the first busbar portion and the third busbar portion form an angle γ1, and the second busbar portion and the third busbar portion form an angle γ2. 100° ≤ γ1 ≤ 170°, and / or, 100° ≤ γ2 ≤ 170°.

[0014] In some embodiments, 120°≤γ1≤150°, and / or, 120°≤γ2≤150°

[0015] In some embodiments, γ1 = 135°, and / or γ2 = 135°.

[0016] In some embodiments, the first busbar portion is perpendicular to the second heat sink; and / or, the second busbar portion is perpendicular to the third heat sink.

[0017] In some embodiments, the plurality of device groups includes two first device groups, two second device groups, and two third device groups. One second device group and one third device group are respectively mounted on opposite sides of the second heat sink along its thickness direction, and another second device group and another third device group are respectively mounted on opposite sides of the third heat sink along its thickness direction. Each of the two second device groups and two third device groups is electrically connected to a busbar. One first device group is electrically connected to the second and third device groups on the second heat sink, and the other first device group is electrically connected to the second and third device groups on the third heat sink.

[0018] In some embodiments, the power module further includes a fifth busbar and a sixth busbar. The second device group and the third device group on the second heat sink are electrically connected to the first busbar portion via the fifth busbar and the sixth busbar, respectively. The fifth busbar includes connected fifth A bends and fifth B bends, and the sixth busbar includes connected sixth A bends and sixth B bends. Both fifth A bends and sixth A bends are parallel to the first busbar portion, and both fifth B bends and sixth B bends are parallel to the second heat sink. The fifth A bend bends from the fifth B bend in a direction away from the second heat sink, and the sixth A bend bends from the sixth B bend in a direction away from the second heat sink.

[0019] In some embodiments, the power module further includes a seventh busbar and an eighth busbar. The second device group and the third device group on the third heat sink are electrically connected to the second busbar portion via the seventh busbar and the eighth busbar, respectively. The seventh busbar includes a seventh A bend and a seventh B bend, and the eighth busbar includes a eighth A bend and an eighth B bend. Both the seventh A bend and the eighth A bend are parallel to the second busbar portion, and both the seventh B bend and the eighth B bend are parallel to the third heat sink. The seventh A bend bends from the seventh B bend in a direction away from the third heat sink, and the eighth A bend bends from the eighth B bend in a direction away from the third heat sink.

[0020] In some embodiments, the busbar includes a stacked first electrode plate, a second electrode plate, and a third electrode plate. The second electrode plate is located between the first and third electrode plates. The first electrode plate is closer to a first side in the thickness direction of the busbar than the third electrode plate. Two second device groups are electrically connected to both the second and third electrode plates. Two third device groups are electrically connected to both the first and second electrode plates. The two third device groups are located inside the second and third heat sinks, respectively. In the first busbar portion, the first electrode plate is shorter than the second electrode plate. Alternatively or supplementarily, in the second busbar portion, the first electrode plate is shorter than the second electrode plate.

[0021] In some embodiments, the power module further includes a plurality of capacitors electrically connected to the busbar, the plurality of capacitors being located on a second side opposite to the first side in the thickness direction of the busbar and mounted on a third busbar portion.

[0022] In some embodiments, each of the multiple device groups includes multiple IGBT devices connected in parallel.

[0023] On the other hand, this invention provides a power conversion device. The power conversion device includes a cabinet and a DC fuse, a DC disconnect switch, a power module provided in the foregoing, a reactor, an AC filter capacitor, and an AC circuit breaker housed within the cabinet and electrically connected in sequence.

[0024] According to embodiments of the present invention, the busbar, power module, and power conversion device both have a first busbar portion and a second busbar portion bent relative to the third busbar portion towards a first side in the busbar thickness direction, thus enabling them to bend towards the second and third heat sinks, respectively. This further reduces the distance from the busbar to the second and third heat sinks, which helps to shorten the length of the busbar connecting the busbar to the device groups mounted on the second and third heat sinks, thereby helping to reduce stray inductance. Attached Figure Description

[0025] Figure 1 is a schematic diagram of the structure of a power module according to an embodiment of the present invention.

[0026] Figure 2 is a structural schematic diagram of the power module in Figure 1 viewed from another direction.

[0027] Figure 3 is an exploded view of a portion of the power module in Figure 1.

[0028] Figure 4 is a schematic diagram of the heat sink with device assembly mounted on the power module in Figure 1.

[0029] Figure 5 is a partial enlarged view of the power module in Figure 2.

[0030] Figure 6 is another enlarged view of the power module in Figure 2.

[0031] Figure 7 is another enlarged view of the power module in Figure 2.

[0032] Figure 8 is another enlarged view of the power module in Figure 2.

[0033] Figure 9 is a schematic diagram of the structure of a power module according to another embodiment of the present invention.

[0034] Figure 10 is a schematic diagram of the structure of a power module according to another embodiment of the present invention. Detailed Implementation

[0035] Numerous specific details are set forth below to provide an understanding of the structure, function, and use of the embodiments described and illustrated in the specification and figures. It is to be understood that the embodiments described and illustrated herein are non-limiting examples, and thus it will be appreciated that the particular structural and functional details disclosed herein are representative and exemplary. Variations and changes may be made to these embodiments without departing from the scope of the claims.

[0036] <Example Power Module>

[0037] This invention provides a power module 10. For ease of understanding, the overall structure of the power module 10 will be described below as an example. It should be understood that the structure of the power module 10 is not limited to the following description. For example, one or more elements (components or parts) mentioned below may be omitted or replaced, and their layout relationships may be changed.

[0038] Referring to Figures 1 to 4, the power module 10 may include a busbar 11, multiple capacitors 12, multiple device groups 13, multiple AC terminals 14, multiple busbars 15, multiple gate plates 16, and multiple heat sinks 17.

[0039] Busbar 11 can provide multiple DC terminals. For example, the multiple DC terminals may include the P terminal, the N terminal, and the O terminal. The P terminal can be electrically connected to the positive terminal of the DC power supply or DC load in the energy storage system. The N terminal can be electrically connected to the negative terminal of the DC power supply or DC load. The O terminal can be connected to the neutral point of the energy storage system, that is, the O terminal can be grounded.

[0040] By way of example only, busbar 11 may include a stacked first electrode plate 11-1, a second electrode plate 11-2, and a third electrode plate 11-3. The second electrode plate 11-2 may be located between the first electrode plate 11-1 and the third electrode plate 11-3. The third electrode plate 11-3 may be located on the side of the first electrode plate 11-1 away from the three heat sinks 17. The first electrode plate 11-1 may provide the N terminal, the second electrode plate 11-2 may provide the O terminal, and the third electrode plate 11-3 may provide the P terminal.

[0041] Multiple capacitors 12 can be electrically connected to busbar 11. Specifically, the multiple capacitors 12 can be directly mounted on busbar 11, located on the side of busbar 11 facing away from the multiple heat sinks 17 in the thickness direction. For example, the multiple capacitors 12 can help maintain voltage stability when the operating current fluctuates, reducing the impact of current on voltage and preventing faults such as overvoltage or undervoltage. Furthermore, the multiple capacitors 12 can filter out noise and interference signals, smoothing the current and improving operational stability and performance.

[0042] The multiple device groups 13 may include multiple first device components 13a, multiple second device groups 13b, and multiple third device groups 13c. A first device component 13a, a second device group 13b, and a third device group 13c may constitute a phase unit. Each phase unit may be electrically connected to the P terminal, N terminal, and O terminal of the busbar 11, and an AC terminal 14.

[0043] Multiple device groups 13 can collectively form six phase units, which are electrically connected to six AC terminals 14a to f. These six phase units can be divided into three pairs of phase units. Each pair of phase units is electrically connected to one phase of the three-phase AC power supply or AC load in the energy storage system via a corresponding pair of AC terminals 14. For example, a pair of AC terminals 14a and 14b can be electrically connected to the U phase of the AC power supply or AC load, a pair of AC terminals 14c and 14d can be electrically connected to the V phase of the AC power supply or AC load, and a pair of AC terminals 14e and 14f can be electrically connected to the W phase of the AC power supply or AC load.

[0044] Gate plate 16 can also be called a drive plate. Multiple gate plates 16 are used to control multiple device groups 13 respectively. During the operation of power module 10, multiple gate plates 16 convert control signals into drive signals. The drive signals act on the gates of multiple device groups 13 to control the on / off state of multiple device groups 13, thereby realizing the power conversion from DC to AC or from AC to DC.

[0045] During operation, the device group 13 generates heat. To prevent overheating, multiple device groups 13 are mounted on multiple heat sinks 17. As a non-limiting example, the heat sink 17 can be implemented as a liquid-cooled plate with flow paths for coolant to flow through, thereby removing heat through the flowing coolant. Of course, other types of heat sinks 17, such as air-cooled heat sinks with heat dissipation fins or gas-liquid phase change plates, are also envisioned.

[0046] The multiple heat sinks 17 may include a first heat sink 17a, a second heat sink 17b, and a third heat sink 17c. The length directions (i.e., the directions perpendicular to the plane of the paper in Figure 2) of the first heat sink 17a, the second heat sink 17b, and the third heat sink 17c may be parallel. The three pairs of phase units may be arranged along the length direction of the heat sinks 17.

[0047] Figure 4 clearly shows three device groups 13 mounted on one side of a heat sink 17 in the thickness direction. These three device groups 13 are arranged along the length of the heat sink 17 and belong to three phase units respectively. Referring to Figure 4, each device group 13 may include multiple devices 131 connected in parallel, and the multiple devices 131 may be arranged along the length of the heat sink 17. As an example, device 131 can be an IGBT device. It is understood that the IGBT device mentioned herein may be the same as conventional IGBT devices; for the sake of brevity, the construction and working principle of the IGBT device will not be described in detail here.

[0048] It is understood that although each device group 13 in FIG. 4 includes four devices 131, in other embodiments of the present invention, each device group 13 may include other numbers of devices 131. For example, in some examples, each device group 13 may include two, three, five or more devices 131.

[0049] As discussed above, each pair of phase units includes six device groups 13: two first device groups 13a, two second device groups 13b, and two third device groups 13c. Here, the two first device groups 13a are electrically connected to two AC terminals 14, which are connected to the same AC phase of the AC power supply or AC load. For example, both AC terminals 14 can be electrically connected to the U phase, or both to the V phase, or both to the W phase. Each second device group is electrically connected to both the P and O terminals, and each third device group is electrically connected to both the N and O terminals. The arrangement of these six device groups 13 on the three heat sinks 17 will be described below.

[0050] Referring to Figures 2 and 3, two first device groups 13a are respectively mounted on opposite sides of the first heat sink 17a in the thickness direction. A second device group 13b and a third device group 13c are respectively mounted on opposite sides of the second heat sink 17b in the thickness direction. Another second device group 13b and another third device group 13c are respectively mounted on opposite sides of the third heat sink 17c in the thickness direction. One first device group 13a on the first heat sink 17a is electrically connected to the second device group 13b and the third device group 13c on the second heat sink 17b to form a phase unit. The other first device group 13a on the first heat sink 17a is electrically connected to the second device group 13b and the third device group 13c on the third heat sink 17c to form another phase unit.

[0051] With this arrangement, under the premise of ensuring that the distance from each first device group 13a to the corresponding second device group 13c and the distance to the corresponding third device group 13c are short and close, the six device groups 13 are arranged on three heat sinks 17, and both sides of each heat sink 17 are fully utilized. This improves the operating power of the power module 10 without significantly increasing the number of heat sinks 17.

[0052] Referring again to Figure 2, the second heat sink 17b and the third heat sink 17c can be located on opposite sides of the first heat sink 17a in the thickness direction. This means that the second and third device groups 13b and 13c on the second heat sink 17b, and the first device group 13a connected to them, will be located on the same side of the first heat sink 17a in the thickness direction, and the second and third device groups 13b and 13c on the third heat sink 17c, and the first device group 13a connected to them, will also be located on the same side of the first heat sink 17a in the thickness direction. This helps to shorten the length of the connecting busbar 15, thereby helping to reduce stray inductance.

[0053] Referring again to Figure 2, the second heat sink 17b and the third heat sink 17c can be located between the first heat sink 17a and the busbar 11. Accordingly, the distances from each second device group 13b to the busbar 11 and to its corresponding first device group 13a are both shorter, and the distances from each third device group 13c to the busbar 11 and to its corresponding first device group 13a are also shorter. Therefore, this arrangement helps to shorten the length of the busbar 15 connecting the two device groups 13 and the length of the busbar 15 connecting the busbar 11 and the device group 13, thereby helping to reduce stray inductance.

[0054] Referring again to Figure 2, the first heat sink 17a and the second heat sink 17b can be arranged at an angle, and / or the first heat sink 17a and the third heat sink 17c can be arranged at an angle, and / or the second heat sink 17b and the third heat sink 17c can be arranged at an angle. Arranging two or three heat sinks 17 at an angle can help improve space utilization and reduce stray inductance.

[0055] It should be noted that in this article, two elements arranged at an angle means that the two elements are not parallel, that is, the angle between the two elements is greater than 0 degrees and less than 180 degrees.

[0056] Referring again to Figure 2, the second heat sink 17b can be tilted towards the first heat sink 17a in a direction away from the busbar 11. Viewed from the perspective of Figure 2, the second heat sink 17b tilts downwards and gradually to the left. If the first heat sink 17a and the second heat sink 17b are arranged parallel to each other, the distance from the second device group 13b on the second heat sink 17b to the corresponding first device group 13a is relatively large, while the distance from the third device group 13c on the second heat sink 17b to the corresponding first device group 13a is relatively small. The difference between the two distances is large, which will result in a large difference in length between the first busbar 15a and the second busbar 15b, increasing stray inductance. In contrast, in this embodiment of the invention, since the second heat sink is arranged to tilt towards the first heat sink 17a in a direction away from the busbar 11, the distance from the second device group 13b on the second heat sink 17b to the corresponding first device group 13a will be shortened, and the distance from the third device group 13c on the second heat sink 17b to the corresponding first device group 13a will be increased, resulting in a smaller difference between the two distances. Therefore, the length difference between the first busbar 15a and the second busbar 15b will be smaller, which helps to reduce stray inductance.

[0057] Referring to Figure 2, the first heat sink 17a and the second heat sink 17b can have an included angle α1, which can satisfy 110°≤α1≤160°.

[0058] If the included angle α1 is too large, close to 180°, the first heat sink 17a and the second heat sink 17b will be arranged nearly parallel. As discussed above, this will result in a large length difference between the corresponding first busbar 15a and the corresponding second busbar 15b, increasing stray inductance. If the included angle α1 is too small, close to 90°, the distance from the second device group 13b on the second heat sink 17b to the corresponding first device group 13a will be small, while the distance from the third device group 13c on the second heat sink 17b to the first device group 13a will be large. The large difference between these two distances will result in a large length difference between the first busbar 15a and the second busbar 15b, increasing stray inductance. Setting the included angle α1 to satisfy the above-described range of the embodiments of the present invention helps to ensure that the length difference between the first busbar 15a and the second busbar 15b is small, thereby helping to reduce stray inductance.

[0059] Preferably, the included angle α1 can satisfy 120°≤α1≤150°.

[0060] In this way, the bending angle of the cable strip 15 between the first heat sink 17a and the second heat sink 17b can be avoided to prevent it from being too large, thereby effectively avoiding the risk of the cable strip 15 breaking.

[0061] More preferably, the included angle α1 can satisfy α1=135°.

[0062] This allows the distance between the wires 15 between the first heat sink 17a and the second heat sink 17b to become more consistent, thereby further reducing stray inductance.

[0063] Alternatively, the included angle α1 can also be any value among 115°, 125°, 130°, 140°, 145°, 155°, 160°, 165°, 170°, and 175°.

[0064] Referring again to Figure 2, the third heat sink 17c can be tilted towards the first heat sink 17a in a direction away from the busbar 11. Viewed from the perspective of Figure 2, the third heat sink 17c tilts downwards and gradually to the right. If the first heat sink 17a and the third heat sink 17c are arranged parallel to each other, the distance from the second device group 13b on the third heat sink 17c to the corresponding first device group 13a will be large, while the distance from the third device group 13c on the third heat sink 17c to the corresponding first device group 13a will be small, resulting in a large difference between the two distances. This will lead to a large difference in length between the third busbar 15c and the fourth busbar 15d, increasing stray inductance. In contrast, in this embodiment of the invention, since the third heat sink 17c is arranged to tilt towards the first heat sink 17a in a direction away from the busbar 11, the distance from the second device group 13b on the third heat sink 17c to the corresponding first device group 13a will be shortened, while the distance from the third device group 13c on the third heat sink 17c to the corresponding first device group 13a will be increased, resulting in a smaller difference between the two distances. Therefore, the length difference between the third busbar 15c and the fourth busbar 15d will be smaller, which helps to reduce stray inductance.

[0065] Referring again to Figure 2, the first heat sink 17a and the third heat sink 17c can have an included angle α2, which satisfies 110°≤α2≤160°. If the included angle α2 is too large, i.e., close to 180°, the first heat sink 17a and the third heat sink 17c will be arranged nearly parallel; as discussed above, this will result in a large difference in length between the third busbar 15c and the fourth busbar 15d, increasing stray inductance. If the included angle α2 is too small, i.e., close to 90°, the distance from the second device group 13b on the third heat sink 17c to the corresponding first device group 13a will be small, while the distance from the third device group 13c on the third heat sink 17c to the corresponding first device group 13a will be large. The large difference between these two distances will result in a large difference in length between the third busbar 15c and the fourth busbar 15d, increasing stray inductance. Setting the included angle α2 to satisfy the above-mentioned range of the embodiments of the present invention helps to ensure that the distance difference between the third line 15c and the fourth line 15d is small, thereby helping to reduce stray inductance.

[0066] Preferably, the included angle α2 can satisfy 120°≤α2≤150°.

[0067] In this way, the bending angle of the cable strip 15 between the first heat sink 17a and the third heat sink 17c can be avoided to prevent it from being too large, thereby effectively avoiding the risk of the cable strip 15 breaking.

[0068] More preferably, the included angle α2 can satisfy α2=135°.

[0069] This allows the distance between the wires 15 between the first heat sink 17a and the third heat sink 17c to become more consistent, thereby further reducing stray inductance.

[0070] Alternatively, the included angle α2 can also be any value among 115°, 125°, 130°, 140°, 145°, 155°, 160°, 165°, 170°, and 175°.

[0071] In a preferred embodiment, continuing to refer to FIG2, the second heat sink 17b and the third heat sink 17c can be arranged symmetrically relative to the first heat sink 17a. This allows the current curves output by the three phase units on the left to converge with those output by the three phase units on the right, reducing mutual interference between the output currents.

[0072] Referring again to Figure 2, the second heat sink 17b can be arranged at an angle to the busbar 11. If the second heat sink 17b is arranged parallel to the busbar 11, the distance from the second device group 13b on the second heat sink 17b to the electrical connection portion 111 (e.g., conductive post) of the busbar 11 is larger, and the distance from the third device group 13c on the second heat sink 17b to the electrical connection portion 111 is smaller. The difference between the two distances is large, which will result in a larger length difference between the fifth busbar 15e and the sixth busbar 15f, increasing stray inductance. In contrast, in this embodiment of the invention, since the second heat sink 17b is arranged at an angle to the busbar 11, the distance from the second device group 13b on the second heat sink 17b to the electrical connection portion 111 will be shortened, and the distance from the third device group 13c on the second heat sink 17b to the electrical connection portion 111 will be increased, resulting in a smaller difference between the two distances. Accordingly, the length difference between the fifth busbar 15e and the sixth busbar 15f will be smaller, which helps to reduce stray inductance.

[0073] Referring again to Figure 2, the second heat sink 17b and the busbar 11 can have an included angle β1, which can satisfy 20°≤β1≤70°.

[0074] If the included angle β1 is too small, i.e., close to 0°, the second heat sink 17b and the busbar 11 will be arranged nearly parallel. As discussed above, this will result in a large length difference between the fifth busbar 15e and the sixth busbar 15f, increasing stray inductance. If the included angle β1 is too large, i.e., close to 90°, the distance from the second device group 13b on the second heat sink 17b to the electrical connection portion 111 will be small, while the distance from the third device group 13c on the second heat sink 17b to the electrical connection portion 111 will be large. The large difference between the two distances will result in a large length difference between the fifth busbar 15e and the sixth busbar 15f, increasing stray inductance. Setting the included angle β1 to satisfy the above-described range of the embodiments of the present invention helps to ensure that the length difference between the two is small, reducing stray inductance.

[0075] Preferably, the included angle β1 can satisfy 30°≤β1≤60°.

[0076] In this way, the bending angle of the busbar 15 between the second heat sink 17b and the busbar 11 can be avoided to prevent it from being too large, thereby effectively avoiding the risk of breakage of the busbar 15.

[0077] More preferably, the included angle β1 can satisfy β1=45°.

[0078] This further makes the distance between the second heat sink 17b and the busbar 11 more consistent, thereby further reducing stray inductance.

[0079] Alternatively, the included angle β1 can also be any value among 25°, 35°, 40°, 50°, 55°, and 65°.

[0080] Referring again to Figure 2, the third heat sink 17c and the busbar 11 can be arranged at an angle. If the third heat sink 17c and the busbar 11 are arranged parallel to each other, the distance from the second device group 13b on the third heat sink 17c to the electrical connection portion 111 of the busbar 11 will be larger, while the distance from the third device group 13c on the third heat sink 17c to the electrical connection portion 111 will be smaller. The difference between the two distances will be large, which will result in a large difference in length between the seventh busbar 15g and the eighth busbar 15h, increasing stray inductance. In contrast, in this embodiment of the invention, since the third heat sink 17c and the busbar 11 are arranged at an angle, the distance from the second device group 13b on the third heat sink 17c to the electrical connection portion 111 will be shortened, while the distance from the third device group 13c on the third heat sink 17c to the electrical connection portion 111 will be increased, resulting in a smaller difference in distance. Accordingly, the difference in length between the seventh busbar 15g and the eighth busbar 15h will be smaller, which helps to reduce stray inductance.

[0081] Referring to Figure 2, the third heat sink 17c and the busbar 11 can have an included angle β2, which can satisfy 20°≤β2≤70°.

[0082] If the included angle β2 is too small, i.e., close to 0°, the third heat sink 17c and the busbar 11 will be arranged nearly parallel. As discussed above, this will result in a large length difference between the seventh busbar 15g and the eighth busbar 15h, increasing stray inductance. If the included angle β2 is too large, i.e., close to 90°, the distance from the second device group 13b on the third heat sink 17c to the electrical connection portion 111 will be small, and the distance from the third device group 13c on the third heat sink 17c to the electrical connection portion 111 will be large. The large difference between the two distances will result in a large length difference between the seventh busbar 15g and the eighth busbar 15h, increasing stray inductance. Setting the included angle β2 to satisfy the above-described range of the embodiments of the present invention helps to ensure that the length difference between the seventh busbar 15g and the eighth busbar 15h is small, reducing stray inductance.

[0083] Preferably, the included angle β2 can satisfy 30°≤β2≤60°.

[0084] In this way, the bending angle of the busbar 15 between the third heat sink 17c and the busbar 11 can be avoided to prevent it from being too large, thus effectively avoiding the risk of breakage of the busbar 15.

[0085] More preferably, the included angle β2 can satisfy β2=45°.

[0086] This allows the distance between the third heat sink 17c and the busbar 11 to be more consistent, thereby further reducing stray inductance.

[0087] Alternatively, the included angle β2 can also be any value among 25°, 35°, 40°, 50°, 55°, and 65°.

[0088] Referring again to Figure 2, in a preferred example, the first heat sink 17a, the second heat sink 17b, and the third heat sink 17c can be arranged in a Y-shape, and the busbar 11, the second heat sink 17b, and the third heat sink 17c can be arranged in a triangular shape. This arrangement of the first heat sink 17a, the second heat sink 17b, the third heat sink 17c, and the busbar 11 has several advantages. On the one hand, according to this arrangement, the second heat sink 17b and the third heat sink 17c will be located on opposite sides in the thickness direction of the first heat sink 17a, and between the first heat sink 17a and the busbar 11. This helps to shorten the length of the busbar 15 connecting them, thereby helping to reduce stray inductance. On the other hand, according to this arrangement, the angles α1 between the first heat sink 17a and the second heat sink 17b, α2 between the first heat sink 17a and the third heat sink 17b, β1 between the second heat sink 17b and the busbar 11, and β2 between the third heat sink 17b and the busbar 11 will satisfy the value range mentioned above, making the length difference of each pair of busbars 15 smaller, which helps to further reduce stray inductance. Furthermore, according to this arrangement, any two of the first heat sink 17a, the second heat sink 17b, the third heat sink 17c, and the busbar 11 will form spaces instead of being in close contact; these spaces help to reduce their mutual influence and improve heat dissipation performance.

[0089] As described above, the multiple busbars 15 may include a first busbar 15a, a second busbar 15b, a third busbar 15c, a fourth busbar 15d, a fifth busbar 15e, a sixth busbar 15f, a seventh busbar 15g, and an eighth busbar 15h. The second device group 13b on the second heat sink 17b can be electrically connected to the corresponding first device group 13a via the first busbar 15a, and the third device group 13c on the second heat sink 17b can be electrically connected to the first device group 13a via the second busbar 15b. The second device group 13b on the third heat sink 17c can be electrically connected to the corresponding first device group 13a via the third busbar 15c, and the third device group 13c on the third heat sink 17c can be electrically connected to the first device group 13a via the fourth busbar 15d. The second device group 13b on the second heat sink 17b can be electrically connected to the P and O terminals of the busbar 11 via the fifth busbar 15e. The third device group 13c on the second heat sink 17b can be electrically connected to the N and O terminals of the busbar 11 via the sixth busbar 15f. The second device group 13b on the third heat sink 17c can be electrically connected to the P and O terminals of the busbar 11 via the seventh busbar 15g. The third device group 13c on the third heat sink 17c can be electrically connected to the N and O terminals of the busbar 11 via the eighth busbar 15h.

[0090] Referring to Figures 2 and 5, the first busbar 15a may include a first A-bend 151a, a first B-bend 152a, and a first C-bend 153a connected in sequence, and the second busbar 15b may include a second A-bend 151b and a second B-bend 152b connected in sequence. Both the first A-bend 151a and the second A-bend 151b are parallel to the first heat sink 17a, and both the first C-bend 153a and the second B-bend 152b may be parallel to the second heat sink 17b. Along the direction away from the busbar 11, i.e., along the downward direction in the figure, both the first A-bend 151a and the second A-bend 151b extend beyond the second heat sink 17b. Thus, the second heat sink 17b will not obstruct the first A-bend 151a and the second A-bend 151b, making it easier to connect the first A-bend 151a and the second A-bend 151b to the first device group 13a, for example, by fasteners.

[0091] Referring to Figures 2 and 6, the third busbar 15c may include a third A bend 151c, a third B bend 152c, and a third C bend 153c connected in sequence, and the fourth busbar 15d may include a fourth A bend 151d and a fourth B bend 152d connected in sequence. The third A bend 151c and the fourth A bend 151d are both parallel to the first heat sink 17a, and the third C bend 153c and the fourth B bend 152d are both parallel to the third heat sink 17c. Along the direction away from the busbar 11, i.e., along the downward direction in the figure, the third A bend 151c and the fourth A bend 151d both extend beyond the third heat sink 17c. In this way, the third heat sink 17c will not block the third A bend 151c and the fourth A bend 151d, making it easier to connect the third A bend 151c and the fourth A bend 151d to the first device group 13a, for example, by fasteners.

[0092] Referring to Figures 2 and 7, the fifth busbar 15e may include a fifth A bend 151e, a fifth B bend 152e, and a fifth C bend 153e connected in sequence, and the sixth busbar 15f includes a sixth A bend 151f and a sixth B bend 152f connected in sequence. Both the fifth A bend 151e and the sixth A bend 151f are parallel to the busbar 11, and both the fifth C bend 153e and the sixth B bend 152f are parallel to the second heat sink 17b. Along a direction away from the first heat sink 17a, i.e., to the right in the figure, both the fifth A bend 151e and the sixth A bend 151f extend beyond the second heat sink 17b. In this way, the second heat sink 17b will not block the fifth A bend 151e and the sixth A bend 151f, making it easier to connect the fifth A bend 151e and the sixth A bend 151f to the electrical connection portion 111 of the busbar 11, for example, by fasteners.

[0093] Referring to Figures 2 and 8, the seventh busbar 15g may include a seventh A bend 151g, a seventh B bend 152g, and a seventh C bend 153g connected in sequence, and the eighth busbar 15h includes an eighth A bend 151h and an eighth B bend 152h connected in sequence. Both the seventh A bend 151g and the eighth A bend 151h are parallel to the busbar 11, and both the seventh C bend 153g and the eighth B bend 152h are parallel to the third heat sink 17c. Along a direction away from the first heat sink 17a, i.e., to the left in the figure, both the seventh A bend 151g and the eighth A bend 151h extend beyond the third heat sink 17c. In this way, the third heat sink 17c will not block the seventh A bend 151g and the eighth A bend 151h, making it easier to connect the seventh A bend 151g and the eighth A bend 151h to the electrical connection portion 111 of the busbar 11, for example, by fasteners.

[0094] Another embodiment of the present invention also provides a power module 10a, which is shown in FIG9. The power module 10a is generally the same as the aforementioned power module 10, the main difference being the busbar 11.

[0095] Referring to Figure 9, the busbar 11 includes a first busbar portion 11a, a second busbar portion 11b, and a third busbar portion 11c. The third busbar portion 11c is located between the first busbar portion 11a and the second busbar portion 11b in the width direction of the busbar 11 (i.e., the left-right direction in Figure 9). Both the first busbar portion 11a and the second busbar portion 11b are bent relative to the third busbar portion 11c towards the first side in the thickness direction of the busbar (i.e., the up-down direction in Figure 9) (i.e., the lower side in Figure 9, the side where the multiple heat sinks 17 are located). That is, the first busbar portion 11a is bent towards the second heat sink 17b, and the second busbar portion 11b is bent towards the third heat sink 17c. This means that the first busbar portion 11a and the third busbar portion 11c are arranged at an angle, and the second busbar portion 11a is also arranged at an angle to the third busbar portion 11c. In this way, the distance from busbar 11 to the second heat sink 17b and the third heat sink 17c will be further reduced, which helps to shorten the lengths of busbars 15e, 15f, 15g, and 15h, thereby helping to reduce stray inductance. Furthermore, the first busbar portion 11a can be perpendicular to the second heat sink 17b, and the second busbar portion 11b can be perpendicular to the third heat sink 17c. This helps to reduce the length difference between busbars 15e and 15f, as well as the length difference between busbars 15g and 15h, thereby reducing stray inductance.

[0096] Further, referring to Figure 9, the first busbar portion 11a and the third busbar portion 11c form an angle γ1, and the second busbar portion 11b and the third busbar portion 11c form an angle γ2. The included angle γ1 can satisfy 100°≤γ1≤170°, and / or the included angle γ2 can satisfy 100°≤γ2≤170°.

[0097] The included angles γ1 and γ2 should not be too large or too small. If the included angle γ1 is too large, that is, close to 180 degrees, the first busbar section 11a will be arranged almost parallel to the third busbar section 11c. This will result in a greater distance between the first busbar section 11a and the device group 13 on the second heat sink 17b, resulting in longer connecting bars 15e and 15f, which in turn will lead to a larger stray inductance. If the included angle γ1 is too small, that is, close to 90 degrees, the bending angle of the first busbar section 11a relative to the third busbar section 11c will be too large, which will increase the risk of busbar 11 breakage. Correspondingly, if the included angle γ2 is too large, that is, too close to 180 degrees, the second busbar portion 11b will be arranged nearly parallel to the third busbar portion 11c. This will result in a greater distance between the second busbar portion 11b and the device group 13 on the third heat sink 17c, leading to longer connecting bars 15h and 15g, and consequently, a larger stray inductance. If the included angle γ2 is too small, that is, close to 90 degrees, the bending angle of the second busbar portion 11b relative to the third busbar portion 11c will be too large, which will also increase the risk of busbar 11 breakage. Setting the included angles γ1 and γ2 to satisfy the above-described ranges of the embodiments of the present invention helps to reduce stray inductance without significantly increasing the risk of busbar 11 breakage.

[0098] Preferably, the included angle γ1 can satisfy 120°≤γ1≤150°, and / or the included angle γ2 can satisfy 120°≤γ2≤150°. On the one hand, according to this range of values, the included angle between the first busbar portion 11a and the third busbar portion 11c, and the included angle between the second busbar portion 11b and the third busbar portion 11c will not be too small, that is, not less than 120 degrees. This ensures that at the bend of the busbar 11, that is, at B1 and B2, the length difference between the first electrode plate 11-1 and the second electrode plate 11-3 will not be too large. On the other hand, based on this range, the angle between the first busbar portion 11a and the third busbar portion 11c, and / or the angle between the second busbar portion 11b and the third busbar portion 11c, will not be too large, i.e., not greater than 150 degrees. This makes the distance from the first busbar portion 11a to the device group 13 on the second heat sink 17b shorter, and the distance from the second busbar portion 11b to the device group 13 on the third heat sink 17c shorter. Combining these two aspects, stray inductance will be further reduced.

[0099] More preferably, the included angle γ1 can satisfy γ1 = 135°, and / or the included angle γ2 can satisfy γ2 = 135°. With these values ​​of included angle γ1 and included angle γ2, combined with the perpendicular arrangement of the first busbar portion 11a and the second heat sink 17b, and the perpendicular arrangement of the second busbar portion 11b and the third heat sink 17c, and with the included angles α1 and α2 between the second heat sink 17b and the third heat sink 17c and the first heat sink 17a being 135°, the second heat sink 17b and the third heat sink 17c will be arranged in a triangular shape with the third busbar portion 11c, and the first heat sink 17a, the second heat sink 17b, and the third heat sink 17c will be arranged in a Y-shape. According to this configuration, the power module 10a will have a lower stray inductance.

[0100] Alternatively, the included angle γ1 can also be any value among 105°, 110°, 115°, 125°, 130°, 140°, 145°, 155°, 160°, and 165°; the included angle γ2 can also be any value among 105°, 110°, 115°, 125°, 130°, 140°, 145°, 155°, 160°, and 165°.

[0101] Referring again to Figure 9, the fifth busbar 15e may include connected fifth A bend 151e and fifth B bend 152e, and the sixth busbar 15f may include connected sixth A bend 151f and sixth B bend 152f. Both fifth A bend 151e and sixth A bend 151f are parallel to the first busbar portion 11a, and both fifth B bend 152e and sixth B bend 152f are parallel to the second heat sink 17b. The fifth A bend 151e bends away from the second heat sink 17b from the fifth B bend 152e, and the sixth A bend 151f bends away from the second heat sink 17b from the sixth B bend 152f. In this way, the second heat sink 17b will not block the fifth A bend 151e and the sixth A bend 151f, making it easier to connect the fifth A bend 151e and the sixth A bend 151f to the busbar 11, for example, by fasteners.

[0102] Referring again to Figure 9, the seventh busbar 15g may include the connected seventh A bend 151g and seventh B bend 152g, and the eighth busbar 15h may include the connected eighth A bend 151h and eighth B bend 152h. Both the seventh A bend 151g and the eighth A bend 151h are parallel to the second busbar portion 11b, and both the seventh B bend 152g and the eighth B bend 152h are parallel to the third heat sink 17c. The seventh A bend 151g bends away from the third heat sink 17c from the seventh B bend 152g, and the eighth A bend 151h bends away from the third heat sink 17c from the eighth B bend 152h. In this way, the third heat sink 17c will not block the seventh A bend 151g and the eighth A bend 151h, making it easier to connect the seventh A bend 151g and the eighth A bend 151h to the busbar 11, for example, by fasteners.

[0103] Preferably, the plane containing the first busbar portion 11a can be perpendicular to the second heat sink 17b; and / or the second busbar portion 11b can be perpendicular to the third heat sink 17c.

[0104] In this way, the distance between the busbar 11 and the device groups 13 on both sides of any heat sink 17 is kept consistent, that is, the current path of the device groups 13 on both sides of the first busbar portion 11a and the second heat sink 17b is the same, and / or the current path of the device groups on both sides of the second busbar portion 11b and the third heat sink 17c is the same, which can reduce stray inductance.

[0105] Referring again to Figure 9, in the first busbar section 11b, the first electrode plate 11-1 is shorter than the second electrode plate 11-2. This allows the fifth A bend 151e to directly face the second electrode plate 11-2, and the sixth A bend 151f to directly face the first electrode plate 11-1. This configuration helps reduce the difficulty of electrically connecting the second device group 13b and the third device group 13c on the second heat sink 17b to the busbar 11.

[0106] Referring again to Figure 9, in the second busbar section 11b, the first electrode plate 11-1 is shorter than the second electrode plate 11-2. This allows the seventh A bend 151g to directly face the second electrode plate 11-2, and the eighth A bend 151h to directly face the first electrode plate 11-1. This configuration helps reduce the difficulty of electrically connecting the second device group 13b and the third device group 13c on the third heat sink 17c to the busbar 11.

[0107] As shown in Figure 9, multiple capacitors 12 can be located on the second side of the busbar 11 in the thickness direction (i.e., the upper side in Figure 9, the side facing away from the multiple heat sinks 17) and mounted on the third busbar section 11c. In this way, the multiple heat sinks 17 and multiple capacitors 12 will be located on opposite sides of the busbar 11 in the thickness direction, and multiple device groups 13 are connected to the first and second busbar sections 11a and 11b, while the multiple capacitors 12 are connected to the third busbar section 11c. According to this arrangement, the electrical connection paths between the multiple device groups 13 and the busbar 11 are shorter, and the electrical connection paths between the multiple capacitors 12 and the busbar 11 are also shorter. Furthermore, all parts of the busbar 11 in the width direction and both sides in the thickness direction are occupied. Therefore, this arrangement balances stray inductance and space utilization, maximizing space utilization while ensuring a low stray inductance, thus achieving the advantages of both low stray inductance and low space occupation.

[0108] The power module according to embodiments of the present invention has been illustrated above. It is understood that the power module according to embodiments of the present invention is not limited to the above description. For example, in a prospective example, as shown in FIG10, the second heat sink 17b and the third heat sink 17c can be arranged in parallel, and the first heat sink 17a can be arranged perpendicular to both of them, such that the three heat sinks 17 as a whole form a T-shaped structure.

[0109] <Exemplary Power Conversion Device>

[0110] This invention provides a power conversion device. The power conversion device includes a cabinet and a DC fuse, a DC disconnect switch, a power module provided in the foregoing, a reactor, an AC filter capacitor, and an AC circuit breaker housed in the cabinet and connected in sequence.

[0111] In particular, the power conversion device provided by the present invention may include two reactors. One reactor can be electrically connected to the AC terminals 14a, 14c, and 14e of three phase units, and the other reactor can be electrically connected to the AC terminals 14b, 14d, and 14f of another three phase units.

[0112] It should be understood that the terms "parallel" and "perpendicular" mentioned in this article should be interpreted as "basically parallel" and "basically perpendicular," respectively, and a reasonable range of error should be included. For example, the range of error can be ±5°.

[0113] It should be understood that the term "comprising" and its variations used in the embodiments of the present invention are open-ended, meaning "including but not limited to". The term "according to" means "at least partially according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least another embodiment".

[0114] It should be understood that although terms such as "first" or "second" may be used in embodiments of the present invention to describe various elements, such as a first heat sink and a second heat sink, these elements are not defined by these terms, which are only used to distinguish one element from another.

[0115] The scope of protection of this invention is not limited to the above embodiments. Any variations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A busbar suitable for use in a power module, characterized in that The busbar includes a first busbar portion, a second busbar portion, and a third busbar portion, the third busbar portion is located between the first busbar portion and the second busbar portion in a width direction of the busbar, and the first busbar portion is bent toward a first side in a thickness direction of the busbar relative to the third busbar portion and arranged at an angle to the third busbar, and the second busbar portion is bent toward the first side in the thickness direction of the busbar relative to the third busbar portion and arranged at an angle to the third busbar.

2. The busbar of claim 1, wherein, The first busbar portion and the third busbar portion form an angle γ1, and the second busbar portion and the third busbar portion form an angle γ2, wherein 100°≤γ1≤170°, and / or 100°≤γ2≤170° 3. The busbar of claim 2, wherein, 120°≤γ1≤150°, and / or 120°≤γ2≤150° 4. The busbar of claim 3, wherein, γ1=135°, and / or γ2=135°.

5. The busbar of any one of claims 1 to 4, wherein, The busbar includes a first busbar portion, a second busbar portion, and a third busbar portion, the third busbar portion is located between the first busbar portion and the second busbar portion in a width direction of the busbar, and the first busbar portion is bent toward a first side in a thickness direction of the busbar relative to the third busbar portion and arranged at an angle to the third busbar, and the second busbar portion is bent toward the first side in the thickness direction of the busbar relative to the third busbar portion and arranged at an angle to the third busbar. In the first busbar portion, the first busbar portion is shorter than the second busbar portion; and / or In the second busbar portion, the first busbar portion is shorter than the second busbar portion.

6. A power module, characterized by Comprise: A plurality of heat dissipation plates, the plurality of heat dissipation plates including a second heat dissipation plate and a third heat dissipation plate; A plurality of device groups, a part of the plurality of device groups are mounted on the second heat dissipation plate, and another part of the plurality of device groups are mounted on the third heat dissipation plate; And A busbar, the second heat dissipation plate and the third heat dissipation plate are located on a first side in a thickness direction of the busbar, the busbar includes a first busbar portion, a second busbar portion, and a third busbar portion, the third busbar portion is located between the first busbar portion and the second busbar portion in a width direction of the busbar, the first busbar portion is bent toward the second heat dissipation plate relative to the third busbar portion and arranged at an angle to the third busbar, and the second busbar portion is bent toward the third heat dissipation plate relative to the third busbar portion and arranged at an angle to the third busbar.

7. The power module of claim 6, wherein, The first busbar portion and the third busbar portion form an angle γ1, and the second busbar portion and the third busbar portion form an angle γ2, wherein 100°≤γ1≤170°, and / or 100°≤γ2≤170° 8. The power module of claim 7, wherein, 120°≤γ1≤150°, and / or 120°≤γ2≤150° 9. The power module of claim 8, wherein, γ1=135°, and / or γ2=135°.

10. The power module of any one of claims 6 to 9, characterized in that, The first busbar portion and the second heat dissipation plate are perpendicular to each other, and / or the second busbar portion and the third heat dissipation plate are perpendicular to each other.

11. The power module according to any one of claims 6 to 10, characterized in that The plurality of device groups comprises two first device groups, two second device groups and two third device groups, one second device group and one third device group are respectively mounted on opposite sides of the second heat sink in the thickness direction, the other second device group and the other third device group are respectively mounted on opposite sides of the third heat sink in the thickness direction, each of the two second device groups and the two third device groups is electrically connected with the busbar, one first device group is electrically connected with the second device group and the third device group on the second heat sink, and the other first device group is electrically connected with the second device group and the third device group on the third heat sink.

12. The power module of claim 11, wherein, The power module further comprises a fifth wire row and a sixth wire row, the second device group and the third device group on the second heat sink are respectively electrically connected with the first busbar part through the fifth wire row and the sixth wire row, the fifth wire row comprises a fifth A bending part and a fifth B bending part connected with each other, the sixth wire row comprises a sixth A bending part and a sixth B bending part connected with each other, the fifth A bending part and the sixth A bending part are both parallel to the first busbar part, the fifth B bending part and the sixth B bending part are both parallel to the second heat sink, the fifth A bending part bends away from the second heat sink from the fifth B bending part, and the sixth A bending part bends away from the second heat sink from the sixth B bending part; and / or The power module further comprises a seventh wire row and an eighth wire row, the second device group and the third device group on the third heat sink are respectively electrically connected with the second busbar part through the seventh wire row and the eighth wire row, the seventh wire row comprises a seventh A bending part and a seventh B bending part connected with each other, the eighth wire row comprises an eighth A bending part and an eighth B bending part connected with each other, the seventh A bending part and the eighth A bending part are both parallel to the second busbar part, the seventh B bending part and the eighth B bending part are both parallel to the third heat sink, the seventh A bending part bends away from the third heat sink from the seventh B bending part, and the eighth A bending part bends away from the third heat sink from the eighth B bending part.

13. The power module according to claim 11 or 12, characterized in that The busbar comprises a first pole plate, a second pole plate and a third pole plate stacked, the second pole plate is located between the first pole plate and the third pole plate, the first pole plate is closer to the first side in the thickness direction of the busbar than the third pole plate, the two second device groups are electrically connected with the second pole plate and the third pole plate, the two third device groups are electrically connected with the first pole plate and the second pole plate, and the two third device groups are respectively located on the inner side of the second heat sink and the third heat sink, wherein In the first busbar part, the first pole plate is shorter than the second pole plate; and / or In the second busbar part, the first pole plate is shorter than the second pole plate.

14. The power module of any one of claims 6 to 13, characterized in that, The power module further includes a plurality of capacitors electrically connected with the busbar, the plurality of capacitors being located on a second side opposite to the first side in the thickness direction of the busbar and mounted on the third busbar portion.

15. The power module of any one of claims 6 to 14, characterized in that, Each of the plurality of device groups includes a plurality of IGBT devices in parallel.

16. A power conversion device, characterized by, The power module is the power module according to any one of claims 6 to 15. The power module is the power module according to any one of claims 6 to 15.

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