Electrical energy system for a vehicle

Abstract

An electrical power system. The electrical power system may include a rechargeable energy storage system (RESS) with a high-voltage (HV) interface configured for exchanging HV power with one or more loads and a low-voltage (LV) interface configured for exchanging LV power with a variety of electrical networks, and a redundant distribution system with a variety of busbars configured for redundantly connecting the electrical networks to the LV interface, so that each of the electrical networks remains operational and connected to the LV interface during a disconnection event.

Description

[0001] This description relates to electrical power systems, such as, but not necessarily limited to, electrical power systems that can be operated on board vehicles to redundantly supply electrical power to multiple grids.

[0002] A vehicle may include an electric motor that converts electrical energy into mechanical energy to perform work with the mechanical energy, e.g., to mechanically drive a powertrain and propel the vehicle. Such vehicles may include a rechargeable energy storage system (RESS) for storing and providing electrical energy, with the RESS typically connected to the electric motor via a high-voltage (HV) interface. Given the relatively large amount of electrical energy available from the RESS, it may be desirable to also use this electrical energy to power other devices, systems, etc. onboard the vehicle.A vehicle may contain a variety of electrical loads operating at relatively lower voltages than the electric motor, with some vehicles containing one or more low-voltage grids (LV grids), buses, etc., to supply the corresponding low-voltage loads. Historically, such vehicles contained a separately operated low-voltage battery connected to one or more low-voltage grids to ensure the supply of electrical power to the low-voltage loads in the event of an interruption or other problem with the RESS, rendering the RESS itself and / or its distribution system unable to reliably supply electrical power to the low-voltage grids.

[0003] DE 10 2022 115 005 A1 describes a vehicle system including a modular storage system with dynamically allocated capacity (MODACS) and an active management module. The MODACS includes cell blocks. The active management module is configured to: detect a first state of a first cell block of the cell blocks; determine, based on the first state of the first cell block, whether a safety fault condition of the first cell block exists; isolate the first cell block from further cell blocks in response to detecting the presence of the safety fault condition; actively discharge and detect a second state of the first cell block after isolating the first cell block, and, based on the second state, continue isolating the first cell block or reconnect the first cell block such that the first cell block is no longer isolated.

[0004] DE 10 2014 201 351 A1 describes an on-board electrical system for a motor vehicle, wherein the on-board electrical system has a low-voltage sub-network for at least one low-voltage consumer and a high-voltage sub-network for at least one high-voltage consumer and a starter-generator, wherein the high-voltage sub-network is connected to the low-voltage sub-network via a coupling unit, wherein the on-board electrical system has a battery which is configured to generate the high voltage and to feed it into the high-voltage sub-network, and which has at least two battery units with individual voltage taps which are connected to the coupling unit.It is provided that the coupling unit is configured to provide at least a first and a second operating state, wherein, in the first operating state, the high-voltage sub-network is fed from all battery units of the battery and the low-voltage sub-network is fed from one battery unit, and, in the second operating state, the high-voltage sub-network is fed from one battery unit and the low-voltage sub-network is fed from at least one battery unit. Furthermore, a method for operating such an on-board electrical system and a motor vehicle with such an on-board electrical system are described.

[0005] The task can be considered to be to provide an improved electrical system for a vehicle in order to reliably supply a low-voltage network with electrical energy.

[0006] The invention relates to an electrical vehicle system with a redundant distribution configuration that allows low-voltage grids, buses, etc., to be reliably supplied with electrical energy during an interruption event, e.g., during an event resulting from a busbar or other connection being unavailable due to a trip or other event. The redundant distribution configuration may have the advantage of eliminating the need or reducing the importance of a low-voltage battery or other backup system for supplying the low-voltage grids with electrical energy independent of a rechargeable energy storage system (RESS).

[0007] The invention relates to an electrical energy system for a vehicle having a traction motor and a plurality of electrical grids. The system includes a rechargeable energy storage system (RESS) having a high-voltage (HV) interface configured to exchange HV power with the traction motor and a low-voltage (LV) interface configured to exchange LV power with the electrical grids. The system further includes a redundant distribution system having a plurality of busbars configured to redundantly connect the electrical grids to the low-voltage interface such that each of the electrical grids remains operational and connected to the low-voltage interface during a disconnection event.

[0008] According to the invention, the electrical networks each comprise an LV busbar configured to distribute the LV power to one or more loads, and the busbars are arranged in a redundant configuration characterized in that each of the LV busbars can be independently connected to two or more busbars.

[0009] The system according to the invention comprises a plurality of generator units, each having a plurality of inputs that can be collectively connected to an output. The generator units each comprise an output connected to one of the low-voltage busbars of the electrical networks and inputs separately connected to one of the two or more busbars.

[0010] According to the invention, the RESS comprises a plurality of cell groups and a plurality of power converters, wherein the power converters are each operable to convert electrical power from one or more cell groups into a plurality of LV outputs, wherein optionally each of the LV outputs supplies corresponding LV power to a location connected to one of the busbars.

[0011] According to the invention, the electrical networks comprise a first network and a second network, and the aggregate units comprise a first unit and a second unit, such that the unit inputs of the first unit comprise a first primary input and a first secondary input, the unit output of the first unit is connected to the first network, the unit inputs of the second unit comprise a second primary input and a second secondary input, and the unit output of the second unit is connected to the second network.

[0012] In one embodiment, the LV outputs of each power converter comprise a first LV output and a second LV output, and the busbars comprise a first and a second busbar such that the first busbar is connected to each of the first LV outputs and the first and second primary inputs and the second busbar is connected to each of the second LV outputs and the first and second secondary inputs.

[0013] In one embodiment, the LV outputs of each of the power converters comprise a first LV output and a second LV output. The system further comprises a distributor having a first distributor input connectable to a distributor output via a first switch or a first fuse, and a second distributor input connectable to the distributor output via a second switch or a second fuse. The busbars may comprise a first busbar, a second busbar, and a third busbar such that the first busbar is connected to each of the first LV outputs, the first primary input, and the first distributor input, the second busbar is connected to each of the second LV outputs, the second secondary input, and the second distributor input, and the third busbar is connected to the first secondary input, the second primary input, and the distributor output.

[0014] In one embodiment, the LV outputs of each power converter comprise a first LV output, a second LV output, and a third LV output, and the busbars comprise a first busbar, a second busbar, and a third busbar such that the first busbar is connected to each of the first LV outputs and the first primary input, the second busbar is connected to each of the second LV outputs and the second secondary input, and the third busbar is connected to each of the third LV outputs, the first secondary input, and the second primary input.

[0015] In one embodiment, the LV outputs of each power converter may include a first LV output, a second LV output, and a third LV output. The system further includes a distribution box having a distribution input connected to a first distribution output via a first switch or fuse and a second switch or fuse, and to a second distribution output via the first switch or fuse and a third switch or fuse.The busbars may comprise a first busbar, a second busbar, and a third busbar such that the first busbar is connected to each of the first LV outputs and the first primary input, the second busbar is connected to each of the second LV outputs and the second secondary input, and the third busbar is connected to each of the third LV outputs, the first secondary input, the second primary input, the distribution input, and the first and second distribution outputs.

[0016] In one embodiment, the LV outputs of a primary side of the power converters each comprise a first LV output and a second LV output, and the LV outputs of a secondary side of the power converters each comprise a third LV output and a fourth LV output. The busbars may comprise a first busbar, a second busbar, a third busbar, and a fourth busbar, such that the first busbar is connected to each of the first LV outputs and the first primary input, the second busbar is connected to each of the second LV outputs and the first secondary input, the third busbar is connected to each of the third LV outputs and the second secondary input, and the fourth busbar is connected to each of the fourth LV outputs and the first primary input.

[0017] In one embodiment, the LV outputs of a primary side of a first plurality of power converters each comprise a first LV output, and a second plurality of power converters each comprise a second LV output, and the LV outputs of a secondary side of a third plurality of power converters each comprise a third LV output, and a fourth plurality of power converters each comprise a fourth LV output. The busbars comprise a first busbar, a second busbar, a third busbar, and a fourth busbar, such that the first busbar is connected to each of the first LV outputs and the second secondary input, the second busbar is connected to each of the second LV outputs and the second primary input, the third busbar is connected to each of the third LV outputs and the first secondary input, and the fourth busbar is connected to each of the fourth LV outputs and the first primary input.

[0018] In one embodiment, the electrical networks comprise a first network and a second network, and the genset units comprise a first unit and a second unit. The unit inputs of the first unit comprise a first primary input, a first secondary input, and a first tertiary input, wherein the unit output of the first unit is connected to the first network. The unit inputs of the second unit comprise a second primary input, a second secondary input, and a second tertiary input, wherein the unit output of the second unit is connected to the second network. The LV outputs of a primary side of the power converters each comprise a first LV output and a second LV output, and the LV outputs of a secondary side of the power converters each comprise a third LV output and a fourth LV output.The busbars include a first busbar, a second busbar, a third busbar, a fourth busbar, and a fifth busbar such that the first busbar is connected to each of the first LV outputs and the second primary input, the second busbar is connected to each of the second LV outputs and the second secondary input, the third busbar is connected to each of the third LV outputs and the first secondary input, the fourth busbar is connected to each of the fourth LV outputs and the first primary input, and the fifth busbar is connected to the first tertiary input and the second tertiary input.

[0019] In one embodiment, the units each comprise a plurality of fuses to connect one of the LV busbars to the two or more busbars.

[0020] In one embodiment, the aggregate units each comprise a plurality of switches for selectively connecting and disconnecting the inputs and the output.

[0021] In one embodiment, the busbars may each have approximately the same length and the same impedance.

[0022] In one embodiment, the interruption event is accompanied by the occurrence of an open circuit on one of the busbars.

[0023] In one embodiment, the disconnection event is accompanied by an open circuit at one of the LV outputs. Fig. 1 shows a schematic view of a vehicle. Fig. Figure 2 shows a schematic diagram of an electrical power system with a redundant distribution configuration. Fig. Figure 3 shows a schematic diagram of an electrical power system with a redundant distribution configuration. Fig. Figure 4 shows a schematic diagram of an electrical power system with a redundant distribution configuration. Fig. Figure 5 shows a schematic diagram of an electrical power system with a redundant distribution configuration. Fig. Figure 6 shows a schematic diagram of an electrical power system with a redundant distribution configuration. Fig. Figure 7 shows a schematic diagram of an electrical power system with a redundant distribution configuration. Fig. Figure 8 shows a schematic diagram of an electrical power system with a redundant distribution configuration.

[0024] Fig. 1 shows a schematic view of a vehicle 10. The vehicle 10, which may be interchangeably referred to as an electric or hybrid vehicle 10, may include an electric motor 12 operable to convert electrical energy into mechanical energy for the purpose of performing work, such as mechanically driving a drivetrain 16 to propel the vehicle. The vehicle 10 is depicted as a hybrid vehicle because the drivetrain 16 optionally includes an internal combustion engine (ICE) 18 for generating mechanical energy. The drivetrain 16 may include a transmission, a driveshaft, a differential, axles, and / or other components to facilitate the transfer of rotational power from the electric motor 12 to one or more of the wheels 20, 22, 24, 26.The vehicle 10 may include a rechargeable energy storage system (RESS) 30, which may be referred to as a battery pack 30, to store and supply electrical energy to the electric motor 12 and / or other systems, buses, etc., connected to one or more electrical grids 34 onboard the vehicle 10. The vehicle 10 may include a battery monitoring system or controller 32 to facilitate monitoring, controlling, measuring, and otherwise controlling operation, performance, etc., onboard the vehicle 10.

[0025] Fig. 2 shows a schematic diagram of an electrical power system 40 with a redundant distribution configuration. The power system 40 may be operated to redundantly supply electrical power from the RESS 30 to the electrical grids 34, which are exemplified by a first electrical grid 34A and a second electrical grid 34B, although more or fewer electrical grids may be included. The RESS 30 may be equipped with a plurality of battery cells arranged according to a plurality of battery groups 42, each battery group connected to a power converter 44. The power converters 44 may be unidirectional and / or bidirectional direct current (DC-DC) converters or other types of devices that may be used to control power transmission.The RESS 30 may include a high-voltage interface 48 and a low-voltage interface 50, wherein the high-voltage interface 48 is operable to exchange high-voltage electrical power with the electric motor 12 and / or a high-voltage bus, and the low-voltage interface 50 is operable via a first connection 52 and a second connection 54 to exchange low-voltage electrical power with the first and second grids 34A, 34B, respectively. The electrical grids 34A, 34B are described as relying on direct current for non-limiting purposes, as this description contemplates one or more of the electrical grids using alternating current (AC), which in this context may include one or more of the power converters 44, which are DC-to-AC converters.

[0026] The energy system 40 may be configured to provide a redundant distribution system having a plurality of bus bars 60, 62 configured to redundantly connect the electrical networks 34A, 34B to the low-voltage interface 50. The redundant configuration may serve to maintain the operability of the electrical networks 34A, 34B during an interruption event, for example, during an event resulting from one of the bus bars 60, 62 and / or another connection being unavailable due to travel or another event. The redundant distribution configuration may have the advantage of eliminating or reducing the need for a low-voltage battery or other backup system to supply electrical energy to the low-voltage networks 34A, 34B independently of the RESS 30 during normal operation, i.e.The electrical grids 34A, 34B may be entirely dependent upon an exchange of electrical energy with the RESS 30. The vehicle 10 may include charging modules or other features (not shown) to facilitate charging the RESS 30 and / or supplying the electrical grids 34A, 34B via charging stations, utility grids, etc., from additional sources external to the vehicle. Other configurations of the RESS 30 are contemplated within the scope of this description, including those that do not rely on separate taps for each battery group 42 and the power converters 44, which in turn may result in different arrangements for the bus bars 60, 62.

[0027] In the illustrated configuration, each of the power converters 44 may be configured to provide a first LV output 64 and a second LV output 66, where the first and second LV outputs 64, 66 may be approximately the same or different. The busbars may include the first busbar 60 connected to each of the first LV outputs 64 and the second busbar 62 connected to each of the second LV outputs 66. The first electrical grid 34A may include a first genset unit 70 that facilitates connection of a first LV busbar 72 to the first and second busbars 60, 62, and the second electrical grid 34B may also include a second genset unit 74 that facilitates connection of a second LV busbar 76 to the first and second busbars 60, 62.The first power unit 70 may include a first primary input 80 and a first secondary input 82 commonly connected to a first output 84, and the second power unit 74 may also include a second primary input 86 and a second secondary input 88 commonly connected to a second output 90. The inputs and outputs 80, 82, 86, 88 are illustrated as being connectable to the outputs 84, 90 via a variety of switches, such as semiconductor, transistor, etc., switches that can be actuated between open and / or closed positions according to commands received from the control unit. A ground (not labeled) is illustrated to represent the power converters 44, the electrical networks 34A, 34B, etc., connected to a vehicle ground, as will be understood by one of ordinary skill in the art to facilitate the operations and configurations contemplated herein.

[0028] Fig. 3 shows a schematic diagram of an electrical power system 40A with a redundant distribution configuration. The electrical system 40A can be distinguished by including a third bus bar 92 and a distribution box 94. The power converters 44 can be configured to provide a first LV output 64 and a second LV output 66. The distribution box 94 can include a first distribution input 96 connectable to a distribution output 98 via a first switch or fuse, and a second distribution input 100 connectable to the distribution output 98 via a second switch or fuse. The first bus bar 60 can be connected to any of the first LV outputs 64, the first primary input 80, and the first distribution input 96.The second busbar 62 can be connected to each of the second LV outputs 66, the second secondary input 88, and the second distribution input 100. The third busbar 92 can be connected to the first secondary input 82, the second primary input 86, and the distribution output 98.

[0029] Fig. 4 shows a schematic diagram of an electrical power system 40B with a redundant distribution configuration. The electrical system 40B can be distinguished by including a third bus bar 92 and each of the power converters with a third LV output 102. The power converters 44 can be configured to provide a first LV output 64 and a second LV output 66. The first bus bar 60 can be connected to any of the first LV outputs 64 and the first primary input 80. The second bus bar 62 can be connected to any of the second LV outputs 66 and the second secondary input 88. The third bus bar 92 can be connected to any of the third LV outputs 102, the first secondary input 82, and the second primary input 86.

[0030] Fig. 5 shows a schematic diagram of an electrical power system 40C with a redundant distribution configuration. The electrical system 40C can be distinguished based on a third bus bar 92, a third LV output 102, and a distribution box 106 having an input 108 and first and second outputs 110, 112. The first bus bar 60 can be connected to any of the first LV outputs 64 and the first primary input 80. The second bus bar 62 can be connected to any of the second LV outputs 66 and the second secondary input 88. The third bus bar 92 can be connected to any of the third LV outputs 102, the first secondary input 82, the second primary input 86, the distribution box input 108, and the first and second distribution box outputs 110, 112.

[0031] Fig. 6 shows a schematic diagram of an electrical power system 40D with a redundant distribution configuration. The electrical system 40D may include a first bus bar 60, a second bus bar 62, a third bus bar 92, a fourth bus bar 114, a fifth bus bar 116, and the generators 70, 74 with an additional tertiary input 120, 122. A primary side 124 of the power converters 44 may each include a first LV output 64 and a second LV output 66, and a secondary side 126 of the power converters 44 may each include a third LV output 130 and a fourth LV output 132. The first bus bar 60 may be connected to each of the first LV outputs 64 and the first primary input 80. The second busbar 62 can be connected to each of the second LV outputs 66 and the first secondary input 82.The third busbar 92 can be connected to any of the third LV outputs 130 and the second tertiary input 122. The fourth busbar 114 can be connected to any of the fourth LV outputs 132 and the second secondary input 88. The fifth busbar 116 can be connected to the first tertiary input 120 and the second primary input 86.

[0032] Fig. 7 shows a schematic diagram of an electrical power system 40E with a redundant distribution configuration. The electrical system 40E can be distinguished by including a third bus bar 92 and a fourth bus bar 114. The LV outputs of a primary side 124 of the power converters 44 can each include a first LV output 64 and a second LV output 66, and the LV outputs of a secondary side 126 of the power converters 44 can each include a third LV output 130 and a fourth LV output 132. The first bus bar 60 can be connected to each of the first LV outputs 64 and the first primary input 80. The second bus bar 62 can be connected to each of the second LV outputs 66 and the second primary input 86. The third bus bar 92 can be connected to each of the third LV outputs 130 and the second secondary input 88.The fourth busbar 114 can be connected to each of the fourth LV outputs 132 and the first secondary input 82.

[0033] Fig.8 shows a schematic diagram of an electrical power system 40F with a redundant distribution configuration. The electrical system 40F can be distinguished in that the third and fourth busbars 92, 114 are connected in different ways. The LV outputs of a primary side 124 of a first plurality of power converters 44 can each include a first LV output 64 and a second plurality of power converters 44 can each include a second LV output 66, and the LV outputs of a secondary side 126 of a third plurality of power converters 44 can each include a third LV output 130 and a fourth plurality of power converters 44 can each include a fourth LV output 132. The first busbar 60 can be connected to each of the first LV outputs 64 and the first primary input 80. The second busbar 62 can be connected to each of the second LV outputs 66 and the first secondary input 82.The third busbar 92 can be connected to any of the third LV outputs 130 and the second secondary input 88. The fourth busbar 114 can be connected to any of the fourth LV outputs 132 and the second primary input 86. The length, diameter, connection to one of the power converters, shape, etc., of the busbars 60, 62, 92, 114 can be varied or dimensioned to adjust the resistances between the power converters 44 and the busbars 72, 76 accordingly.

Claims

[1] Electrical energy system (40) for a vehicle (10) having a traction motor (12) and a plurality of electrical networks (34), comprising: a rechargeable energy storage system, RESS (30), having a high-voltage interface, HV (48), configured to exchange high-voltage energy with the traction motor (12), and a low-voltage interface, LV (50), configured to exchange low-voltage energy with the electrical grids (34); and a redundant distribution system having a plurality of bus bars (60, 62, 92, 114, 116) configured to redundantly connect the electrical grids (34) to the low-voltage interface (50) such that each of the electrical grids (34) remains operational and connected to the low-voltage interface (50) during a disconnection event; where: the electrical networks (34) each comprise an LV busbar (72, 76) configured to distribute the LV power to one or more consumers; and the busbars (60, 62, 92, 114, 116) are arranged in a redundant configuration, characterized by that each of the LV busbars (72, 76) can be independently connected to two or more of the busbars (60, 62, 92, 114, 116); wherein the electrical power system (40) further comprises: a plurality of aggregate units (70, 74), each having a plurality of inputs (80, 82, 86, 88) which can be commonly connected to an output (84, 90), wherein the aggregate units (70, 74) each comprise the output (84, 90) which is connected to one of the LV busbars (72, 76) of the electrical networks (34), and the inputs (80, 82, 86, 88) are separately connected to one of the two or more of the busbars (60, 62, 92, 114, 116); where: the RESS (30) comprises a plurality of cell groups (42) and a plurality of power converters (44), each of the power converters (44) being operable to convert electrical power from one or more of the cell groups (42) to a plurality of LV outputs (64, 66), each of the LV outputs (64, 66) supplying corresponding LV power to a location connected to one of the busbars (60, 62, 92, 114, 116); and where: the electrical networks (34) comprise a first and a second network (34A, 34B); and the aggregate units (70, 74) comprise a first unit (70) and a second unit (74), and wherein the electrical energy system (40) characterized by is that: the unit inputs (80, 82) of the first unit (70) comprise a first primary input (80) and a first secondary input (82); the unit output (84) of the first unit is connected to the first network (34A); the unit inputs (86, 88) of the second unit (74) comprise a second primary input (86) and a second secondary input (88); and the unit output (90) of the second unit is connected to the second network (34B). [2] Electrical energy system (40) according to claim 1, wherein: the LV outputs (64, 66) of each of the power converters (44) comprise a first LV output (64) and a second LV output (66); and the busbars (60, 62, 92, 114, 116) comprise a first busbar (60) and a second busbar (62), wherein: the first busbar (60) is connected to each of the first LV outputs (64) and the first and second primary inputs (80, 86); and the second busbar (62) is connected to each of the second LV outputs (66) and the first and second secondary inputs (82, 88). [3] Electrical energy system (40) according to claim 1, further comprising: the LV outputs (64, 66) of each of the power converters (44) comprise a first LV output (64) and a second LV output (66); a distribution box (94) having a first distribution input (96) connectable to a distribution output (98) via a first switch or fuse, and a second distribution input (100) connectable to the distribution output (98) via a second switch or fuse; and the busbars (60, 62, 92, 114, 116) comprise a first busbar (60), a second busbar (62), a third busbar (92), wherein: the first busbar (60) is connected to each of the first LV outputs (64), the first primary input (80) and the first distribution input (96); the second busbar (62) is connected to each of the second LV outputs (66), the second secondary input (88) and the second branch input (100); and the third busbar (92) is connected to the first secondary input (82), the second primary input (86) and the distributor output (98). [4] Electrical energy system (40) according to claim 1, wherein: the LV outputs (64, 66, 102) of each of the power converters (44) comprise a first LV output (64), a second LV output (66) and a third LV output (102); and the busbars (60, 62, 92, 114, 116) comprise a first busbar (60), a second busbar (62) and a third busbar (92), wherein: the first busbar (60) is connected to each of the first LV outputs (64) and the first primary input (80); the second busbar (62) is connected to each of the second LV outputs (66) and the second secondary input (88); and the third busbar (92) is connected to each of the third LV outputs (102), the first secondary input (82) and the second primary input (86). [5] The electrical power system (40) of claim 1, further comprising: that the LV outputs (64, 66, 102) of each of the power converters (44) comprise a first LV output (64), a second LV output (66) and a third LV output (102); a distribution box (106) having a distribution input (108) connected via a first switch or a fuse and a second switch or a fuse is connected to a first distribution output (110) and via the first switch or the first fuse and a third switch or a third fuse is connected to a second distribution output (112); and the busbars (60, 62, 92, 114, 116) comprise a first busbar (60), a second busbar (62), a third busbar (92), wherein: the first busbar (60) is connected to each of the first LV outputs (64) and the first primary input (80); the second busbar (62) is connected to each of the second LV outputs (66) and the second secondary input (88); and the third busbar (92) is connected to each of the third LV outputs (102), the first secondary input (82), the second primary input (86), the distribution input (108) and the first and second distribution outputs (110, 112). [6] Electrical energy system (40) according to claim 1, wherein: the LV outputs (64, 66) of a primary side (124) of the power converters (44) each comprise a first LV output (64) and a second LV output (66), and the LV outputs (130, 132) of a secondary side (125) of the power converters (44) each comprise a third LV output (130) and a fourth LV output (132); and the busbars (60, 62, 92, 114, 116) comprise a first busbar (60), a second busbar (62), a third busbar (92) and a fourth busbar (114), wherein: the first busbar (60) is connected to each of the first LV outputs (64) and the first primary input (80); the second busbar (62) is connected to each of the second LV outputs (66) and the first secondary input (82); the third busbar (92) is connected to each of the third LV outputs (130) and the second secondary input (88); and the fourth busbar (114) is connected to each of the fourth LV outputs (132) and the first primary input (80).

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