Patent Publication Number: US-2021168960-A1

Title: Integrated direct mount branch protection for variable frequency drive

Description:
BACKGROUND OF THE INVENTION 
     Embodiments of the invention relate generally to variable frequency drives and, more particularly, to a variable frequency drive having a branch protection device directly mounted thereto, so as to provide integrated direct mount branch protection for the variable frequency drive. 
     One type of system commonly used in industry that performs power conversion is an adjustable speed drive, also known as a variable frequency drive (VFD). A VFD is an industrial control device that provides for variable frequency, variable voltage operation of a driven system, such as an AC induction motor. In use, a VFD is often provided as part of a motor control system and overall control and protection assembly that includes the VFD as well as an arrangement of input/output fuses, disconnects, circuit breakers or other protection devices, controllers, filters, sensors, and a bypass assembly that includes one or more of a bypass contactor and soft starter that provide alternate control paths or mechanisms for controlling the driven system. 
     In a common configuration, the VFD and associated branch protection devices are provided as discrete components having their own housings. The discrete, housed components are then each separately mounted to a common, fixed metal back panel that, in turn, may be mounted to a wall. While such an arrangement and mounting of the VFD and associated branch protection devices provides for a workable motor control system, it is recognized that there are drawbacks associated therewith regarding the overall size/footprint of the system, the number of mounting brackets and fasteners required for such mounting, and the cost of the arrangement due to the requirement of the separate back panel. 
     It would therefore be desirable to provide a VFD and associated branch protection device integrated therewith that provides a reduced size/footprint of the overall arrangement and that minimizes the number of mounting brackets and fasteners required for mounting the devices. It would further be desirable for the VFD and integrated branch protection device to be cost competitive with existing systems/arrangements and be easy to assemble and install. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with one aspect of the invention, a power protection and conditioning arrangement includes a VFD having a VFD housing and a power conversion circuit contained within the VFD housing and operable to provide a controlled output power to a load. The power protection and conditioning arrangement also includes a branch protection device having a branch protection housing and a power protection circuit contained within the outer housing and operable to selectively interrupt current flow from a power source to the VFD during a fault condition. The branch protection device is coupled to the VFD, such that the branch protection device is integrated with the VFD. 
     In accordance with another aspect of the invention, an integrated power protection and conditioning system includes a VFD operable to provide a controlled output power to a load and a branch protection device operable to selectively interrupt current flow from a power source to the VFD during a fault condition, wherein a branch protection box of the branch protection device is mounted directly to a housing of the VFD to integrate the branch protection device with the VFD. 
     In accordance with yet another aspect of the invention, a method for providing an integrated power protection and conditioning system includes providing a branch protection device comprising a branch protection box enclosing branch protection circuitry operable to selectively interrupt current flow and mounting the branch protection device to a VFD comprising a housing enclosing power conversion circuitry operable to provide a controlled output power to a load, wherein mounting the branch protection device to the VFD comprises coupling the branch protection box to the housing, such that the branch protection device is integrated with the VFD. 
     Various other features and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate preferred embodiments presently contemplated for carrying out the invention. 
       In the drawings: 
         FIG. 1  is a schematic diagram of a power system. 
         FIG. 2  is a perspective view of a variable frequency drive and integrated branch protection device of the power system of  FIG. 1 , with the branch protection device being integrated with the VFD, according to an embodiment of the invention. 
         FIG. 3  is an exploded perspective view of the variable frequency drive and integrated branch protection device of  FIG. 2 . 
         FIG. 4  is a perspective view of the branch protection device in isolation, according to an embodiment of the invention. 
         FIG. 5  is a perspective view of the variable frequency drive in isolation, according to an embodiment of the invention. 
         FIG. 6  is a perspective view of the mounting bracket that mounts the branch protection device to the variable frequency drive, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to providing integrated direct mount branch protection for a variable frequency drive. A branch protection device is mounted directly to a VFD without the requirement of a separate, common fixed metal back panel. The integrated branch protection device and VFD thus provides a compact unit with a reduced number of mounting components and fasteners that is cost competitive and easy to assemble and install. 
     While embodiments of the invention are described here below as being directed to a VFD with an integrated branch protection device, it is recognized that embodiments of the invention are not meant to be limited to such circuits. That is, embodiments of the invention may be extended more generally to power/energy conversion circuits of varying constructions and implementations, including motor starters, motor control centers, and power/energy conversion circuits for driving non-motor loads, for example. Accordingly, the following discussion of a VFD with an integrated branch protection device is not meant to limit the scope of the invention. 
     Referring to  FIG. 1 , a schematic diagram of a power system  10  is illustrated. Power system  10  includes a power source  12 , such as from a utility, for example, coupled to a branch protection device  14  that may be operated so as to selectively allow or block a flow of power therethrough. According to embodiments of the invention, branch protection device  14  may be in the form of a disconnect contactor or switch that may be operated in a closed or On position in which power from source  12  is allowed to flow therethrough and an open or Off position in which power may not flow therethrough, or in the form of a circuit breaker that provides overcurrent protection by interrupting the current from power source  12  if the level of current becomes too high. 
     Branch protection device  14  is coupled to a VFD  16  that operates to provide a controlled output power to a load  18  (e.g., motor). As known in the art, VFD  16  includes power control circuitry  20  therein, such as an arrangement of solid state switches, e.g., IGBTs, that may be controlled via an associated control system or controller (not shown) operably coupled thereto in order to provide a controlled output from the power converter  16 . The operation of VFD unit  16  enables driving and adjusting the operating speed of load/motor  18 , which can be used to drive fans, conveyors, pumps, or other electromechanical devices. 
     Referring now to  FIGS. 2-6 , a power protection and conditioning arrangement formed by the branch protection device  14  and VFD  16  is illustrated, as well as a mounting bracket for mounting the branch protection device  14  directly to the VFD  16 . Various perspective views of the power protection and conditioning arrangement are shown to better illustrate a construction of the components and the integration of the components according to an exemplary embodiment of the invention. As will be explained in greater detail below, branch protection device  14  is mounted directly to a VFD  16  without the requirement of a separate, common fixed metal back panel. The integrated branch protection device  14  and VFD  16  thus provides a compact unit with a reduced number of mounting components and fasteners that is cost competitive and easy to assemble and install. 
     As shown in  FIGS. 2, 3, and 4 , branch protection device  14  includes a branch protection box or housing  24  that houses protection circuitry  26  therein. The branch protection box  24  generally includes side surfaces  28 , front surface  30 , back surface  32 , bottom surface  34 , and top surface  36 . The front surface  30  includes a control feature  38  thereon, such as a knob or dial, that may be used to reset the branch protection device  14 , such as resetting a circuit breaker after tripping thereof. The top surface  36  includes one of more openings  42  therein through which power supply cables or conduits  44  (generally see  FIG. 1 ) may pass out from the branch protection device  14  and to VFD  16 . Side surfaces  28  of branch protection box  24  each include a plurality of fastener holes  45  formed therein. 
     As shown in  FIGS. 2, 3 and 5 , VFD  16  includes an outer housing  46  that houses power conditioning circuitry  24  ( FIG. 1 ) therein. The housing  46  of VFD  16  may generally include a front portion  48  and a rear portion  50 . The front portion  48  comprises a control front panel  52  and the rear portion  50  comprises a back mounting surface  54  configured to provide for securing of the VFD  16  to a wall or other panel provided to support the VFD  16 . The VFD housing  46  also includes a bottom surface  56  that includes a plurality of openings formed therein that comprise a plurality of fastener holes  57  as well as one of more openings  58  through which power supply cables or conduits  44  may pass into the VFD  16 . According to an exemplary embodiment, an arrangement of six electrical conduit openings  58  are formed in bottom surface  56  of the VFD housing  46 , so as to enable input and output of 3-phase power to/from the VFD  16 . 
     According to an exemplary embodiment, and as shown in  FIGS. 3 and 6 , a mounting bracket  60  is provided between the branch protection device  14  and VFD  16  that provides for mounting of the devices together. The mounting bracket  60  is constructed to have what may be characterized as a U-shaped structure, with a pair of side legs  62  spaced apart and extending down from a connecting leg  64 . Each of the side legs  62  includes a plurality of fastener holes  65  formed therein whose number and spacing correspond to the fastener holes  45  formed in the side surfaces  28  of branch protection box  24 , although in an exemplary embodiment fastener holes  65  are of a larger size than fastener holes  45  formed in the side surfaces  28  of branch protection box  24 . According to an exemplary embodiment, two fastener holes  65  are formed in each of the side legs  62 , although it is recognized that a greater or lesser number of fastener holes  65  could be provided. The connecting leg  64  also includes a plurality of fastener holes  40  formed therein whose number and spacing correspond to the fastener holes  57  formed in the bottom surface of VFD housing  46 . Additionally, the connecting leg  64  includes one of more openings  66  formed therein through which power supply cables or conduits  44  may pass from the branch protection device  14  into the VFD  16 . According to an exemplary embodiment, an arrangement of three electrical conduit openings  66  are formed in connecting leg  64  of the mounting bracket  60 , so as to enable 3-phase supply power to be provided to the VFD  16 . 
     To secure the branch protection device  14  to the VFD  16 , the mounting bracket  60  is first positioned below and adjacent the VFD housing  46  such that fastener holes  40  on the connecting leg  64  of the mounting bracket  60  align with the fastener holes  57  on the bottom surface  56  of the VFD housing  46 . Fasteners  67  are then inserted through the fastener holes  40  of mounting bracket  60  and passed through the fastener holes  57  of VFD housing  46  to secure the mounting bracket  60  to the VFD  16 . Upon such alignment, openings  66  in connecting leg are aligned with at least a portion of openings  58  in bottom surface  56  of the VFD housing  46 , so as to enable routing of power supply cables/conduits into the VFD  16 , with additional openings in bottom surface  56  of the VFD housing  46  being left uncovered so as to provide for a routing of output power from the VFD  16  to a connected load  18 . Upon securing of the mounting bracket  60  to the VFD  16 , the branch protection box  24  is then slid up into mounting bracket  60  such that fastener holes  65  on the side legs  62  thereof align with the fastener holes  45  on the side surfaces  28  of the branch protection box  24 . Fasteners  68  are then inserted through the fastener holes  65 ,  45  to secure the branch protection box  24  to the mounting bracket  60 . 
     In mounting the branch protection device  14  directly to the VFD  16 , it is recognized that the branch protection device  14  has a weight that may require modifications to be made to the VFD housing  46  beyond what a standard housing  46  would entail. Thus, according to an embodiment, the VFD housing  46  is modified such that the bottom surface  56  thereof is reinforced so as to be able to sufficiently bear a weight of the branch protection device  14 . Such reinforcing of the bottom surface  56  may be achieved via a forming of the VFD housing  46  of a thicker gauge material or metal or via the use of additional brackets running from side surfaces  28  of the VFD housing  46  to the bottom surface  56 . 
     Beneficially, embodiments of the invention thus provide a VFD and associated branch protection device integrated therewith that provides a reduced size/footprint of the overall arrangement and that minimizes the number of mounting brackets and fasteners required for mounting the devices. A separate back panel to which the VFD and associated branch protection device may be separately mounted is eliminated. The VFD and integrated branch protection device is cost competitive with existing systems/arrangements and is easy to assemble and install. 
     According to one embodiment of the present invention, a power protection and conditioning arrangement includes a variable frequency drive (VFD) having a VFD housing and a power conversion circuit contained within the VFD housing and operable to provide a controlled output power to a load. The power protection and conditioning arrangement also includes a branch protection device having a branch protection housing and a power protection circuit contained within the outer housing and operable to selectively interrupt current flow from a power source to the VFD during a fault condition. The branch protection device is coupled to the VFD, such that the branch protection device is integrated with the VFD. 
     According to another embodiment of the present invention, an integrated power protection and conditioning system includes a VFD operable to provide a controlled output power to a load and a branch protection device operable to selectively interrupt current flow from a power source to the VFD during a fault condition, wherein a branch protection box of the branch protection device is mounted directly to a housing of the VFD to integrate the branch protection device with the VFD 
     According to yet another embodiment of the present invention, a method for providing an integrated power protection and conditioning system includes providing a branch protection device comprising a branch protection box enclosing branch protection circuitry operable to selectively interrupt current flow and mounting the branch protection device to a VFD comprising a housing enclosing power conversion circuitry operable to provide a controlled output power to a load, wherein mounting the branch protection device to the VFD comprises coupling the branch protection box to the housing, such that the branch protection device is integrated with the VFD. 
     The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.