Abstract:
A battery charging system which includes an input circuit configured to receive an input power and provide an output power on a first output terminal and a second output terminal. An output circuit has a first input terminal connected to the first output terminal and a second input terminal connected to the second output terminal to receive the output power and configured to condition the output power for a battery charging process. A first conductive plate with a first bus surface extends between the first input terminal and the first output terminal. An insulator plate has a first insulator surface disposed in an abutting relationship with the first bus surface and a second insulator surface. A second conductive plate has a second bus surface which extend between the second input terminal and the second output terminal and is disposed in an abutting relationship with the second insulator surface.

Description:
REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     The present invention relates generally to battery charging systems and, more particularly, to a planar bus for a fast-charging battery charging systems. 
     BACKGROUND OF THE INVENTION 
     Fast-charging, battery charging systems are distinguished from other battery charging systems in that they operate to produce a battery charging output with a higher kilowatt output and approximately twice, or greater, the charging rate than traditional battery charging systems. An industrial-type, fast charging, battery charging system can include a power supply connected to one or more charging stations, and the charging stations can have output currents up to 500 A or greater, and power outputs up to 30 kW and greater. Compatible battery voltages are typically 12 to 80 volts from a lead-acid battery or battery bank. The industrial-type, fast charging, battery chargers can typically be used for charging lift trucks, fork lifts, golf carts, and the like, which chargers operate at relatively higher electrical power levels to charge a 12-80 volts direct current (VDC) battery system. In these systems, the battery is the main power source for driving the fork lift, golf cart, and the like. 
     These fast charging systems can have a primary side switched-mode power supply that converts a mains alternating current (AC) electrical power into a suitable direct current (DC) electrical power. A chopping circuit may also be included to convert the DC electrical power to charging power. In general terms, the switched-mode power supply can include input terminals for mains input, and an input rectifier and filter for filtering and rectifying the mains input, an inverter for converting the rectified input power to a higher frequency, a high frequency transformer which converts the voltage up or down to the required output level on its secondary winding(s), and another rectifier and/or output chopper circuit to provide a suitable DC battery charging power. Mains power can be 120, 240, 480, 600, or higher, VAC, and single phase or multiphase being typical for the higher voltages. A switched-mode power supply has the advantage of providing a relatively high frequency to the transformer, which allows the transformer to be smaller for a given current capacity, as transformer size is inversely related to operating frequency. 
     Fast-charging, battery charger, power supplies can generally require a number of heat generating electrical devices such as transformers, power modules which may have insulated gate bipolar transistor (IGBT) switching modules, inductors, rectifiers, transducers and the like interconnected through busses or bus bars, circuit boards, connectors, cables, etc. Because of the high current and/or voltages involved, such power supplies can have electrical devices as mentioned that generate a considerable amount of heat which needs to be dissipated in order to prevent damage to the battery charging power supply, and to increase the reliability of the battery charging power supply. Some of these devices (e.g., transformers) are relatively robust, whereas other (e.g., the integrated circuits used on the power modules and other circuit boards) are susceptible to contaminants and other elements such as static electricity. 
     Typically, the initial rectified voltage is provided to a bus (i.e., a conductor or conductors that provides a fixed or varying potential to a variety of components), which is disposed across a capacitor bank for filtering. The inverter (switched circuit) then inverts the electrical power and converts it to a higher frequency. Some designs, such as those including chopper circuits, have a second bus which is further processed by the output circuit. 
     It is also well know that fast-charging battery charging systems can become hot during use. Components can be cooled by blowing air past them, but it is also known that blowing air can bring particles past sensitive components, such as integrated circuits, switches, etc., which could damage them. Thus, there are competing concerns, cooling components and keeping components safe from dirt, other contaminants, etc. 
     Higher output fast-charging battery charging systems have a bus or bus bar that can become very hot due to the high currents and corresponding I 2 R heating. Generally, as the battery charging current output rises, the bus or bus bar must be able to dissipate more heat. Prior art designs do not adequately address the design of bus or bus bars to reduce/dissipate heat so that they do not need to have air blown past them. Bus or bus bar(s), as used herein, can refer to one bus or bar (or bar at one potential), or multiple busses or bars at different potentials, and bus or bar refers to the conductor, not a particular shape. 
     Accordingly, what is needed in the art is a fast-charging battery charging system power supply that has a bus and/or a bus assembly that can be used at high current without overheating, and which has inherent heat dissipation capabilities. 
     SUMMARY OF THE INVENTION 
     Generally, the invention provides for a battery-charging power supply with a planar bus, wherein the layers include an insulator plate sandwiched between two bus bars, preferably in the shape of plates. The bus bars are at different potentials in operations, and the bus voltage is the voltage difference across the bars. Planar bus, as used herein includes a bus comprised of layers in a fixed relation to one another. They can be fixed with adhesive, fasteners, etc. Insulator plate, as used herein, includes an insulating material where the surface area is large relative to the thickness. Conductive plate, as used herein, includes a conductor having a surface area large relative to the thickness. 
     The invention comprises, in one form thereof, a battery charging system which includes an input circuit configured to receive an input power and provide an output power on a first output terminal and a second output terminal. An output circuit has a first input terminal connected to the first output terminal and a second input terminal connected to the second output terminal to receive the output power and configured to condition the output power for a battery charging process. A first conductive plate with a first bus surface extends between the first input terminal and the first output terminal. An insulator plate has a first insulator surface disposed in an abutting relationship with the first bus surface and a second insulator surface. A second conductive plate has a second bus surface which extend between the second input terminal and the second output terminal and is disposed in an abutting relationship with the second insulator surface. 
     The invention comprises, in another form thereof, a battery charging system which includes an input circuit with a rectifier for receiving and rectifying an input electrical power thereby producing a rectified electrical power, the input circuit having a first output terminal and a second output terminal for outputting the rectified electrical power. A switched circuit has a first input terminal and a second input terminal for receiving the rectified electrical power, and the switched circuit includes at least one switch for transforming the rectified electrical power to a switched power. An output circuit is connected to the switched circuit to receive the switched power and produce a battery charging power. Battery charging cables are connected to the output circuit to receive the battery charging power. A bus assembly connects the input circuit to the switched circuit. The bus assembly includes a first bus plate extending along a first plane and configured to carry a positive charge and a second bus plate extending along a second plane and configured to carry a negative charge. 
     The invention comprises, in yet another form thereof, a method of manufacturing a bus assembly in a battery charger, where the bus assembly connects an input circuit which has a first output terminal and a second output terminal, and a switched circuit which has a first input terminal and a second input terminal. The method comprises the steps of: providing a bus including a first conductive plane and a second conductive plane separated by an insulating layer; connecting the first conductive plane to the first output terminal and the first input terminal; connecting the second conductive layer to the second output terminal and the second input terminal; and isolating the first conductive plane from the second conductive plane by arranging a substantially planar electrical isolator to abut the first conductive plane along a first side and the second conductive plane along a second side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of an embodiment of a battery charging system according to the present invention, shown with a lift truck and a forklift; 
         FIG. 2  is a perspective view of the power supply of the battery charging system of  FIG. 1 ; 
         FIG. 3  is a perspective view of the power supply of  FIG. 2 , with part of the cover removed; 
         FIG. 4  is a perspective view of the bus assembly used in the power supply of  FIG. 2 ; 
         FIG. 5  is an exploded of the bus assembly of  FIG. 4 ; 
         FIG. 6  is a simplified schematic view of the power supply of  FIG. 2 ; 
         FIG. 7  is a perspective view of another embodiment of a bus assembly according to the present invention; and 
         FIG. 8  is an exploded perspective view of the bus assembly of  FIG. 7 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIG. 1 , a battery charging system  20  includes battery-charging, power supply  22  that provides a battery charging energy over cables  26 . While a centralized battery-charging, power supply  22  is shown, it is also contemplated that the present invention may be utilized in other battery-charging, power supply/charging stations systems, daisy-chain power supply arrangements, and the like. Battery-charging cables  26  connect to, and provide a battery-charging power (such as a DC current at an appropriate battery system voltage) for, the battery systems of lift truck  30 , forklift  32 , and/or other battery powered systems. Battery charging system  20  can also include a battery module (not shown) which is carried by, and is connected to, the battery systems of vehicles  30 ,  32  and the like, and provides some control and monitoring to assess battery health and the charging process, charging and discharging history, and download capability for these parameters to provide fleet operations data. 
     Battery-charging, power supply  22  can include a display  34  that may indicate charge level, charge time, charge voltage, and other relevant parameters of the charging process. Battery-charging, power supply  22  can also include on/off, and other, controls; short circuit, ground fault, and/or other electrical anomaly sensing circuits; feedback circuits providing feedback from the sensing circuits to the control circuits; and other terminals, connectors, controls and circuits as are known. 
     Referring now to  FIGS. 2-3  and  6 , battery charger power supply  22  can include a housing structure with a base  38 , sides  40  (only one shown), top cover  42 , front panel  44 , rear panel  46 , and A-frame assembly  48 . Louvers  45  can be part of front panel  44  and/or rear panel  46 , and fan  47  can be connected to rear panel  46 . The overall circuit schematic is shown in  FIG. 6  which illustrates a source of electrical power  50  (such as an electrical mains connection) which is connected to an input circuit  52 . Electrical mains source  50  is typically a three phase source of electrical, but can also be a single phase, or two phase, circuit. Input circuit  52  is connected to bus assembly  54 , which is connected to output circuits  56  having switched circuits  58  and filter circuits  60 . Alternatively, filter circuit  60  can be considered an output circuit 
     Input circuit  52  as used herein includes any circuit capable of receiving an input signal from a source of power and providing an output signal to a battery charging switched circuit, and can include a primary box  62  (which may have input fuses, terminal strips and other connectors and components) for receiving the input electrical power  50  and a three phase transformer  64  connected thereto, and which is supported by A-frame assembly  48 . Input circuit  52  includes a rectifier which rectifies the output of transformer  64 . Input circuit  52  can include as part of its circuitry, microprocessors, analog and digital controllers, switches, other transformers, other rectifiers, inverters, electrical chokes, converters, choppers, comparators, phased controlled devices, buses, pre-regulators, diodes, inductors, capacitors, resistors, fuses, etc. 
     Output circuit  56  as used herein includes any circuit capable of receiving an input signal from an input circuit and providing an output signal suitable for a battery charger-type output signal (e.g., suitable for battery charging). Output circuits can include microprocessors, analog and digital controllers, switches, other transformers, rectifiers, inverters, electrical chokes, converters, choppers, comparators, phased controlled devices, buses, pre-regulators, diodes, inductors, capacitors, resistors, etc. In particular, filter circuit  60  can include output filter chokes  66 , output capacitors  68  and output fuse block  70 . While the illustrated embodiment shows output circuit  56  as including two sets of switched circuits  58  and filter circuits  60  arranged in parallel, other configurations are contemplated. For example, only one switched circuit  58  and filter circuit  60  may be included or other combinations of switched circuits  58  and filter circuits  60 . 
     In the embodiment of  FIGS. 1-6 , and referring more particularly to  FIGS. 4 and 5 , switched circuit  58  is at least partially integrated into bus assembly  54 . IGBT-diode switching-rectifying modules  72  extend within housing  74 , and are also connected to heat sink  76 . Each of modules  72  include a negative input terminal  78  and a positive input terminal  80  which are connected to respective negative bus plate  82  and a positive bus plate  84 . Each of modules  72  also include at least one output terminal  81  to connect to a corresponding filter circuit  60 . Although switching modules  72  preferably include IGBTs, they can have other switches. Capacitors  86  include positive terminal  88  and negative terminal  90  are inside housing  74 ; however, the bulk of the capacitors are outside housing  74 . Also, switching-rectifying modules  72  are primarily inside housing  74 , but are thermally connected to heat sink  76  which is outside housing  74 . Housing  74  can be enclosed with a cover (not shown), and in which case, does not have forced liquid flow, and can be made of metal, plastic or other rigid material. Because heat sink  76  and capacitors  86  are primarily outside of housing  74 , a fan can force air flow past these hot components, and provide the necessary cooling. The design of plates  82  and  84  allow for sufficiently reduced heating and improved heat dissipation to avoid the need for having airflow past these bus plates. Thus, housing  74  may be enclosed, protecting the components therein. 
     A bus  92  in accordance with an embodiment of the present invention includes a conductive negative bus plate  82 , an insulator plate  94  and a conductive positive bus plate  84  abutting against one another, which are mounted in housing  74 . Plate  82  is electrically connected to a negative terminal of each of capacitors  86  of the capacitor bank, and to the negative terminal of parallel switch modules  72 . Plates  82 ,  84 ,  94  include holes therethrough for fasteners to attach to the positive terminals  80 ,  88  to a corresponding positive bus plate  84 , and negative terminals  78 ,  90  to a corresponding negative bus plate  82 , and/or to affix the plates in position. Plate  82  has a long dimension of over about 11 inches and a width of over about 7 inches. The surface area is approximately 70 square inches. The thickness or depth of plate  82  is preferably about 0.125 inches. Thus, the ratio between the surface area (sq. in.) and thickness (in.) is about 560 (the ratio is different for different measuring units). The greater cross-section (7 in.×0.125 in.) allows for less heat because there is less impedance, and thus less heating, while the greater surface area (approximately 7 in.×11 in.) allows for more heat dissipation. The thin profile saves cost and weight. Various embodiments provide for ratios of surface area (sq. in.) to thickness (in.) of at least 200:1 or 400:1. Plates  82 ,  84  and  92  have similar holes therethrough, although in some instances the holes are clearance holes for the fasteners which attach to the terminals, and in other instances, the holes are clearance holes for the terminals but are smaller than the fasteners in order to attach a specific terminal to a specific plate, as is shown in  FIGS. 4 and 5 . Plates  82 ,  84  and  92  have similar dimensions and ratios although notably negative bus plate  82  is slightly larger in order to connect to the negative terminals  78 ,  90 . (Thickness, as used herein, refers to the dimension perpendicular to the larger surfaces of the plate.) 
     Housing  74  can include knockout  96  which allows for electrical connection between plates  82 ,  84  and output terminals  98 ,  100  of input circuit  52 ; and another knockout  97  to connect switch modules  72  to a corresponding filter circuit  60 . Further, each one of the switched circuits  58  in  FIG. 6  includes, and is essentially, a single switching-rectifying module  72 . 
     Power supply  22  can include other elements such as current sensor  99 , which is part of the control loop for charger  22 . Additionally, and as is shown by the dashed lines in  FIG. 6 , the outputs of filter circuits  60  can be connected in parallel to provide a faster charging rate. 
     In the embodiment of  FIGS. 7 and 8 , bus assembly  102  includes two heat sinks  104 , each of which are thermally connected to two switching-rectifying modules  106 . In this embodiment, which generally has a higher battery-charging power output than the embodiment of  FIGS. 4 and 5  (30 kW versus 20 kW, for example), there are two switching-rectifying modules  106  in parallel for each switched circuit  58 . Each of modules  106  include a negative input terminal  108  and a positive input terminal  110  which are connected to respective negative bus plate  114  and a positive bus plate  116 , of bus  118 . Each of modules  106  also include at least one output terminal  120  to connect to a corresponding filter circuit  60 . Capacitors  122  replace capacitors  86  and include negative terminals  124  and positive terminals  126  which are arranged to connect to respective negative bus plate  114  and a positive bus plate  116 , of bus  118 . As with bus assembly  54 , bus assembly  102  includes conductive plates  114  and  116 , in addition to insulator plate  128 . Plates  114 ,  116  and  128  of characteristics similar to  82 ,  84  and  94 , although they have a different hole layout to accommodate the different topology of bus assembly  102 . 
     While example embodiments and applications of the present invention have been illustrated and described, including a preferred embodiment, the invention is not limited to the precise configuration and resources described above. Various modifications, changes, and variations apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and systems of the present invention disclosed herein without departing from the scope of the claimed invention.