Abstract:
A casting for a housing for a flexible, configurable power converter is disclosed. The housing includes a power compartment that is configured to accept a heat sink in either of two orientations. The configurable nature of the power converter allows the same power convertible package to be used in a number of applications without having to incur the cost of developing a new power converter package.

Description:
TECHNICAL FIELD 
     The present disclosure relates to a flexible design of a casting for a housing of a power converter. The flexible design allows for the power converter to support the drivetrain needs of a product line of machines without having to design and tool a new casting for each application. 
     BACKGROUND 
     Power converters are commonly used to convert AC power from a generator to DC power, and then from DC power to AC power for use by a motor. Power conversion may require high-speed switching of large currents by power semiconductor devices, such as insulated gate bipolar transistors (IGBTs). An electric drive traction application typically includes both AC/DC conversion to receive power from a generator and DC/AC conversion to power a motor. The generator is typically driven by an engine. 
     Different power converter applications may also have different requirements for locations of external connections. Such connections may include DC connections, AC connections, coolant connections, control connections, and accessory connections. Power converters may be used in different locations on a machine, and each location may require different locations for the connections. For example, a power converter may be connected to a generator or a motor, each of which is located on a different part of the machine. Likewise, if the machine has two or more drive motors, a power converter may require different locations for the connections. For example, motors on the front and rear or left and right sides of the machine may require connection locations that are mirror images of the other. This would normally require a new power converter to be developed for each location. 
     The cost of designing a power converter is considerable. Significant engineering time is required for proper bus bar routing, board layouts, housing design, and power module design. The design cost for power modules is particularly high. Tooling is also an important consideration. For example, the tooling for a single housing design can be in excess of $100,000. Each time a new power converter is designed for a new application, new tooling is needed. Typically, a single housing design cannot be used for different power converter designs. 
     Accordingly, the power converter is a significant portion of an electric drivetrain cost. Production volumes are needed to drive down costs in order to make electric drivetrains feasible for more applications in a product line. Therefore it is desirable to design a power converter package that can be adapted to a large number of configurations while changing a minimum number of components. Thus, the power converter design can fulfill the needs of an entire product line of electric drivetrains thereby saving NRE and tooling costs associated with creating new designs for every application. 
     United States Patent Application No. 20060120001 to Weber et al., issued Jun. 8, 2006, entitled “Modular power supply assembly,” known hereafter as the Weber Reference. The Weber Reference discloses “A modular power converter that is easily adapted to a wide variety of applications . . . . ” However, The Weber Reference takes a very different approach from the current disclosure and states that “A fundamental approach of the present design is to separate the typical drive inverter and converter design functions of a power converter into separate assemblies.” Different parts of the chassis or housing are changed out in order to adapt to different applications. The number of different parts requires a large number of designs in order to meet the needs of those applications. In addition, the heat sink design disclosed by Weber et al. does not account for coolant connections from different sides of the power converter. 
     SUMMARY OF THE INVENTION 
     A casting for a power converter housing is disclosed. The casting comprises a front side, a back side which is opposite from the front side and has a power compartment, a top side, and a bottom side which is opposite from the top side. The casting further comprises a right side a left side opposite from the right side. A power compartment is located on said back side, having a recess configured to receive a heat sink mounted in one of two orientations. The heat sink comprises a first end and a second end, the first end having coolant ports configured to receive coolant, a set of mounting features configured to align with a set of mounting holes in the casting when mounted in either of two orientations. The casting further comprises a first heat sink orientation that provides coolant ports on the right side of said housing and a second heat sink orientation provides coolant ports on the left side of said housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a housing according to the current disclosure 
         FIG. 2  is a front view of a housing according to the current disclosure 
         FIG. 3  is a back view of a housing according to the current disclosure 
         FIG. 4  is a back view of a housing according to the current disclosure 
         FIG. 5  is a view of a heat sink according to the current disclosure 
         FIG. 6  is a view of a heat sink mounted to a housing according to the current disclosure 
         FIG. 7  is a configuration table according to the current disclosure 
         FIG. 8  is a drivetrain configuration according to the current disclosure 
         FIG. 9  shows casting features included on casting according to the current disclosure 
         FIG. 10  shows features included on a housing according to the current disclosure 
     
    
    
     DETAILED DESCRIPTION 
     The power converter package  10  includes a housing  20 . The housing is made of metal and is cast and/or machined. The housing has a front  30  and a front cover  32  that covers a front compartment  34 . The front compartment  34  contains an interface board  200  that connects to a controller  202  through a controls connector  140 . The interface board  200  provides signal processing between the controller  202  and the gate drive boards  110  and sensors, etc. in the power converter package  10 . The housing  20  includes provisions to allow the controls connector  140  be mounted on either of the left or right sides. The housing  20  also includes provisions to allow a DC connection box to be mounted on either of the left or right sides. 
     The housing  20  also has a back  40  and a back cover  42  that covers a back compartment  44 . The back compartment  44  has provisions for mounting a filter capacitor  70 , a heat sink  50 , an accessory connector  160 . The housing  20  includes provisions to allow the accessory connector  160  mounted on either of the left or right sides. 
     Provisions are included in the housing  20  that allow the DC connection box  120 , controls connector  140 , the accessory connector  160  to be mounted on either the left or right side. For instance, casting features  330  such as mounting bosses are included on both left and right sides to allow mounting of the DC connection box  120 . Finish machining, drilling, and tapping may then be performed in either location depending on where the DC connection box  120  needs to be mounted for a particular application. Casting features  330  are also provided to allow for a DC connection aperture  122  in the casting  15  in order to allow DC connections to pass from the DC access bar  130  to the DC connection box  120 . The application may require one, two, or no DC connection boxes  120 . Casting features  340  that provide for controls connector  140  includes a flat that can be machined and mounting bosses to allow mounting on either the left or right side. Similarly, casting features  350  are provided for the accessory connector  160  to be mounted on either the left or right side. 
     The housing  20  includes an AC connection compartment  180  at one end. The AC connection compartment  180  provides access for AC power connection from outside the housing  20  to the components inside the housing  20 . Connections are provided via lug-and-gland type connectors from the AC cables  190  to a terminal block  80 . Access is provided by a front AC connection plate  170 , a back AC connection plate  172 , and a bottom AC connection plate  174 . The AC connection plates are attached to the housing  20  via mounting flanges. Any of the AC connection plates can be configured with cable apertures  176  to allow AC cables  190  to pass through. In this fashion, AC cables  190  may be routed to the power converter package  10  from the front, back or bottom. 
     The heat sink  50  bolts to the housing  20  inside the housing back compartment  44 . The housing back compartment  44  includes a recess  46  configured to accept the heat sink  50 . One surface of the heat sink  50  is machined flat and includes power module mounting holes  52  for mounting a plurality of power modules  60 . Coolant passages are provided that route through the heat sink  50  to remove heat generated by the power modules  60 . The heat sink  50  and housing  20  are configured such that the heat sink  50  can be mounted with the coolant inlet/outlet connections  150  on either of the left or right side. The housing  20  includes a housing interface  56  that is added to accommodate the end of heat sink  50  and provide apertures for coolant inlet/outlet connections  150 . The casting  15  includes a first casting feature  320  that allows the housing interface  56  to be located on either of the left or right sides of the casting  15 . 
     The heat sink includes mounting features or mounting holes  54  for the bolts that attach the heat sink  50  to the housing  20  are arranged in symmetry about the left-right axis  210  allowing the heat sink  50  to be attached to the housing in either of two orientations. In this way, the power converter package  10  can provide coolant inlet/outlet connections  150  on either the left or right side while using the same housing  20  and heat sink  50 . In one aspect of the current disclosure, the power module mounting holes  52  that attach the power modules  60  to the heat sink  50  are configured with a symmetry about the left-right axis  210  of the power converter package  10 , allowing proper mounting of the power modules  60  in either mounting configuration. In another aspect of the current disclosure, the power module mounting holes  52  located in the heat sink  50  are symmetric about a left-right axis of the heat sink  50 . 
     The power modules  60  typically include paired silicon-based insulated gate bipolar transistors (IGBTs) and fly-back diodes. The IGBTs are enclosed in a case and electrically connected to connection terminals. Connection terminals are also included for connection of the IGBT gates to a gate drive board  110 . A backing plate is thermally connected to the IGBTs and diodes. Heat generated by the IGBTs during switching is conducted through the backing plate and into the heat sink  50  where it can be removed by circulating coolant. Mounting holes are provided through the case and backing plate for mounting the power modules  60  to the heat sink  50 . 
     The power converter package  10  according to the present disclosure is designed to work with either induction/PM or switched reluctance (SR) technology. Induction/PM and SR technology require power modules  60  with different configurations. An induction/PM power module  62  is configured with both IGBTs in series. Three induction/PM power modules  62  in a power module set  66  are typically used to provide three-phase AC that connects to a stator winding of an induction/PM machine such as a motor or generator. An SR power module  64  is configured with both IGBTs in parallel and provides power for one stator winding of an SR machine such as a motor or generator. SR power modules  64  in a power module set  66  can be combined to provide AC power to multi-phase SR machines. 
     Though possible, it is inefficient from a space and cost perspective to use an induction/PM configuration to power an SR machine. As such, power converters are not typically designed to accommodate both induction/PM and SR technology. A power converter package  10  that can accommodate both induction/PM and SR technology would require a power module  60  that is available in both induction/PM and SR configurations. This power module  60  is available as an induction/PM power module  62  and an SR power module  64  and is available exclusively from Infineon Industrial Power Division of Lebanon, N.J. The induction/PM power module  62  and SR power module  64  have identical mounting and DC connection configurations and are therefore mechanically interchangeable save for the start/finish and AC connections. Filter capacitors  70  are mounted in the housing back compartment  44  and are electrically connected to the DC bus bar  90  via screw terminals. The mounting arrangement of the filter capacitors  70  is designed to accommodate high vibration environments. The filter capacitors  70  provide bulk capacitance that is needed to dampen ripple current that occurs on the DC link that connects the power converter package  10  to loads or different power conversion stages. The bulk capacitance also serves to filter out harmonic content and voltage spikes of the DC link voltage. Film capacitors are often the preferred choice for mobile applications and can be packaged and mounted in a variety of ways. 
     The power converter package  10  includes a terminal block  80  that connects the AC bus bars  100  to the AC cables  190 . Connecting lugs on the terminal block  80  extend into the AC connection compartment  180  where they connected to the AC cables  190  via lug-and-gland style connections. The terminal block  80  includes a printed circuit board (PCB) with a soldered hall-effect current sensor and a plastic isolator with conductors. The pieces are assembled together as a sub-assembly and then assembled into the power converter package  10 . The assembly is capable of conducting and sensing current for any number of conductors as needed for the power converter application. The combination of hall-effect sensor and conductor assembly results in a smaller and less expensive solution than the industry standard approach. 
     The terminal block  80  is designed in configurations with two, three, or four connector lugs. The three configurations or combinations of the three configurations of terminal blocks  80  is sufficient to meet all the required applications of the power converter package. 
     The DC bus bar  90  connects the positive and negative DC terminals of the power module  60  to the respective terminals of the filter capacitor  70 . The DC bus bar  90  is formed by laminating two conductors together, where each of the conductors is individually insulated from the other conductor. 
     Provisions to connect to the DC bus bar  90  to an accessory connector  160  and a DC access bar  130  are provided. Said provisions can be in the form of threaded terminals, crimp lugs, or the like. The DC bus has properties of symmetry about the left-right axis  210  and has provisions to connect to the DC bus bar  90  to an accessory connector  160  and a DC access bar  130  on the left and right side. 
     The DC access bar  130  is a two conductor laminated bus bar that connects the DC bus bar  90  to the DC connection box  120 . A first end of the DC access bar  130  can connect to the DC bus bar  90  in either of two locations. The second end of the DC access bar  130  connects to a DC terminal block that is mounted to the bottom of the DC connection box  120 . The DC access bar has properties of symmetry and is designed to connect to the DC connection box  120  whether the DC connection box  120  is mounted on the left or the right side of the housing  20 . 
     The DC connection box  120  is a connection box that can be located on either the left, right, or both sides of the housing  20 . The DC connection box  120  provides access for DC power connection from outside the housing  20  to the components inside the housing  20 . The DC connection box  120  includes a DC terminal block that is mounted to the housing at the base of the DC connection box and is electrically connected to the DC access bar  130 . Connections are provided via lug-and-gland type connectors from the DC cables  192  to the DC terminal block. In some applications, an external DC bus bar may be used instead of DC cables  192 . 
     The gate drive board  110  is configured to take commands from a controller  202  through the interface board  200  and generate switching commands for the power modules  60 . Switching commands are given to the power modules  60  via connectors carrying control-level voltage signals. The gate drive board  110  of the current disclosure is designed in two configurations. The first configuration supports a single power module  60 . The second configuration supports two power modules  60  that are connected in parallel. Either configuration is able to support an induction/PM power module  62  or an SR power module  64 . 
     The power converter package  10  of the current disclosure is designed to be adapted to a large number of configurations while changing a minimum number of components. The power converter package  10  is therefore configurable to fulfill the needs of an entire product line of electric drivetrains  310  and the need to design and pay for tooling all new components for each application is avoided. 
     For example, the housing  20 , heat sink  50 , filter capacitor  70 , and DC bus bar  90  are common between every power converter package  10  configuration. In addition, only one power module  60  footprint serves all power converter package  10  configurations. 
     Symmetry is a major theme among many components, including the housing  20 , heat sink  50 , power module  60 , DC bus bar  90 , DC connection box  120 , and DC access bar  130 . Symmetry in shape and mounting configuration allows such components to be mounted in different locations within the power converter package  10  or able to be combined with different versions of other components without modification. 
     The table in  FIG. 7  shows the configurations that are able to be satisfied by the power converter package  10 , including the topologies, and major components. The major topologies will be briefly described below. 
       FIG. 9  shows various casting features of the casting  15 .  FIG. 10  shows the housing  20  after several machining operations. 
     INDUSTRIAL APPLICABILITY 
     The power converter package  10  of the current disclosure is designed to be adapted to a large number of configurations while changing a minimum number of components. The power converter package  10  is therefore configurable to fulfill the needs of an entire product line of electric drivetrains  310  for providing tractive effort on a machine  5 . This saves NRE and tooling costs associated with creating new designs for every application. Further, using a single power converter package  10  across an entire product line increases volume which lowers the cost of the power converter package  10  by diluting the NRE and tooling costs over a larger volume. Since the power converters can be a significant portion of the cost of an electric drivetrain  310 , this allows electric drivetrains  310  to be incorporated in more applications. 
     To this end, the housing  20 , heat sink  50 , filter capacitors  70 , and DC bus bar  90  are common between every configuration. In addition, the power converter package  10  is designed to use one power module  60  footprint that supports both SR and induction/PM technology. This capability allows the power converter package  10  to connect to either an SR or induction/PM motor or generator while changing a minimum number of components. 
       FIG. 8  shows another example of an electric drivetrain  310  according to the present disclosure. The power converter packages  10  shown are of the type SR Parallel Topology  270 . The first power converter package  10  is connected to an SR generator  230  by a first set of six AC cables  190 . The generator  230  is driven by a prime mover such as an internal combustion engine. The AC cables  190  from the generator  230  are electrically connected to a first power module set  66  of six SR power modules  64  configured in parallel. An SR motor  220  is connected to a second power converter package  10  by a second set of six AC cables  190 . The AC cables  190  from the motor  220  are electrically connected to a second power module set  66  of six SR power modules  64 . The first and second power converter packages  10  are connected by DC cables  192 . The electric drivetrain  310  is configured such that, in normal operation, power flows from the generator  230 , through the first power converter package  10 , to the second power converter package  10 , and to the motor  220 . The electric drivetrain  310  is configured such that power can also flow from the motor  220 , through the second power converter package  10 , through the first power converter package  10 , and to the generator  230 . The SR Dual Topology  270  as shown in  FIG. 8  is typically rated for around 650 V dc and 1400 A rms. 
     The electric drivetrain  310  in  FIG. 8  shows the DC connection box  120 , the controls connector  140 , the coolant inlet/outlet connections  150 , and the accessory connector  160  on one side of the power converter packages  10 . It should be understood that any of the preceding features could be located on either of the left or rights sides in any combination as required by the application. Further, the AC cables  190  could be routed to either the front, back or rear of the power converter package  10 .