Patent Publication Number: US-10327354-B1

Title: Server rack architecture that facilitates reduced current density

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of, and claims priority to, U.S. patent application Ser. No. 15/943,755, filed on Apr. 3, 2018, which is a continuation application of, and claims priority to, U.S. patent application Ser. No. 15/179,390, filed on Jun. 10, 2016, which is a divisional application of, and claims priority to, U.S. patent application Ser. No. 13/798,759, filed on Mar. 13, 2013. The disclosure of the foregoing application is incorporated herein by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The subject disclosure relates to server racks and more particularly to optimizing current distribution by reducing current density within a server rack. 
     BACKGROUND 
     Server racks are used to house multiple computer servers and other related loads, and to provide power and communication signals to them. A server rack uses busses to distribute the current generated by power supply units (PSUs) to the loads situated on various shelves of the server rack. In conventional server rack architecture, the PSUs are located on either the top shelf or the bottom shelf of the server rack, and the current generated by them is distributed to the various loads by using a vertical bus. The vertical bus location closest to the PSUs is subjected to maximum current density. The current density progressively decreases at vertical bus locations away from the PSUs. Conventional server rack architecture requires oversized busses that can support the maximum possible current density that can be generated by the PSUs. Oversized busses are undesirable because they require more space and increased material costs than smaller busses. 
     SUMMARY 
     The following presents a simplified summary of the specification in order to provide a basic understanding of some aspects of the specification. This summary is not an extensive overview of the specification. It is intended to neither identify key or critical elements of the specification nor delineate any scope of particular aspects of the specification, or any scope of the claims. Its sole purpose is to present some concepts of the specification in a simplified form as a prelude to the more detailed description that is presented later. 
     According to an implementation of the subject disclosure, a server rack having vertically stacked shelves and vertically stacked PSUs is disclosed. Two vertical busses are secured to the back side of the server rack and are located substantially at the left and right sides of the server rack respectively. Multiple horizontal busses, that are parallel to each other, are coupled between the two vertical busses. Each horizontal bus is coupled to two PSUs and to one or more servers. The server rack as a whole can be oriented in a device, system or room vertically, horizontally or at an angle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Numerous aspects, implementations, objects and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  illustrates a front view of a server rack, according to an implementation of the subject disclosure. 
         FIG. 2  illustrates a rear view of a server rack having vertical bus bars and horizontal busses. 
         FIG. 3  illustrates a rear view of a server rack having divided horizontal busses. 
         FIG. 4  illustrates a rear view of a server rack having divided vertical bus bars and divided horizontal busses. 
         FIG. 5  illustrates a rear view of a server rack having a central vertical bus bar. 
         FIG. 6  illustrates a rear view of a server rack having a divided vertical bus bar. 
         FIG. 7  illustrates an exemplary graphical representation of a battery power module for use in a server rack demonstrating architecture for enhanced power distribution. 
         FIG. 8  illustrates an exemplary isometric graphical representation of a battery power module and a server rack. 
         FIG. 9  illustrates a flow diagram of an exemplary method for assembling an efficient server rack. 
         FIG. 10  illustrates an example methodology for hot swapping a server rack component. 
         FIG. 11  illustrates an exemplary graphical representation of a server rack including separable racks for housing PSUs. 
     
    
    
     DETAILED DESCRIPTION 
     Implementations of the subject disclosure are described below with references to the above drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the subject disclosure. It is to be appreciated, however, that the subject disclosure can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the subject disclosure. 
     As discussed herein, the terms N, N+1 and N+M are used herein according to their ordinary meanings. Also, N, N+1 and N+M are used interchangeably herein. M can be 0 or 1 or another integer number. As discussed herein, components are coupled to one another securely, hinged or removably. Secure and hinged are used with their usual meanings. Removable coupling includes any fastening that provides lateral stability without being permanently fixed. For example, removably coupled components can be removed using a single tool, such as a screwdriver. In a nonlimiting implementation, removable coupling can include mere placement of a component on top of a shelf, whereby gravity and friction or physical objects such as other components provide lateral stability. In a nonlimiting implementation, removable coupling includes the use of a tray that slides. Other nonlimiting examples of secure or removable coupling include adhesives, screws, clips, clamps, interference fits and pins. 
     As discussed herein, hot swappable means the power supply units can be removed during continuous operation of the other components on the server rack. By having components that are removably coupled, the server rack architecture disclosed herein facilitates components being hot swappable. As discussed herein, a load is a device that uses electrical power or communications from the server rack and is electrically coupled to other components on the server rack. The terms server, load, and component as used herein, are interchangeable. In a nonlimiting implementation, a video monitor is the load. In a non-limiting implementation, multiple servers or loads are placed on each shelf in a server rack. 
       FIG. 1  illustrates an exemplary front view of a server rack  100 . The server rack  100  includes two side posts ( 105   1  and  105   2 ) which are vertically oriented and contain compartments for housing power supply units. A first shelf ( 110   1 ) is securely coupled to and located toward the upper ends of the posts ( 105   1  and  105   2 ). The first shelf ( 110   1 ) can extend into the posts ( 105   1  and  105   2 ) and create the compartments for housing the PSUs ( 120   1 ,  120   2 ). A second shelf ( 110   2 ) is securely coupled to the posts ( 105   1  and  105   2 ) and is generally located below the first shelf ( 110   1 ). It is to be understood that any number of shelves ( 110   N ) can be coupled to the posts ( 105   1  and  105   2 ) and located above or below other shelves ( 110   1 ,  110   2 ,  110   N ) in the rack  100 . Furthermore, it is to be understood that any type of secure coupling can be used to attach shelves ( 110   1 ,  110   2 ,  110   N ) to posts ( 105   1  and  105   2 ) in a way that fixes their location and provides structural rigidity to the server rack  100 . 
     Servers ( 130   1 ,  130   2 ,  130   N ) are placed on top of the shelves ( 110   1 ,  110   2 ,  110   N ) respectively and generally placed at the center of their respective shelves, equidistant from the first and second sides. Each shelf ( 110   1 ,  110   2  or  110   N ) can house one or more servers (e.g.  130   1 ) of same or different form factors. The servers (e.g.  130   1 ,  130   2 ,  130   N ) can be removably coupled to the shelves ( 110   1 ,  110   2 ,  110   N ). In nonlimiting implementations, a load (e.g.  130   1  can also include any combination of appliances, data center components, server system components, communication components, AC components, DC components and electronic devices. 
     The power supply units (or modules) ( 120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) include power converters and backup power sources. In an implementation, the power distribution units controllers (e.g.  140   1  and  140   2 ) provide an AC fuse function or circuit breaker function and are removably coupled to a power control shelf ( 145 ) of the server rack  100 . Furthermore, removable coupling allows the PDUs ( 140   1  and  140   2 ) to be hot swappable. In an implementation, the power control shelf (e.g.  145 ) is located above the first shelf ( 110   1 ). In an implementation, the PDUs ( 140   1  and  140   2 ) provide the initial AC power input connection for the server rack  100 . In an implementation, the PDUs ( 140   1  and  140   2 ) are electrically coupled to the power supply modules ( 120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ). In an implementation, the power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) convert AC input to DC output. In an implementation, power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) are mounted separate and external to server rack  100 . 
     In an implementation, power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) are electronic assemblies of batteries coupled to power converters. In an implementation, the power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) are removably coupled to the shelves (e.g.  110   1 ,  110   2 ,  110   N ). Removable coupling allows the power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) to be hot swappable. Power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   N , 120 M+1 ) are electrically coupled to loads (e.g.  130   1 ,  130   2 ,  130   N ). Power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M ,  120   M+1 ) invert or transform AC or DC input into AC or DC output for use by the loads (e.g.  130   1 ,  130   2 ,  130   N ). The server rack  100  can be placed inside or attached to a system, device or room at various orientations including vertically, horizontally or at an angle. 
       FIG. 2  illustrates a rear view  200  of the power distribution components in an exemplary server rack. Viewed from the back side of the server rack  100 , an array of electrical distribution busses (including e.g.  250   1 ,  250   2 ,  260   1 ,  260   2 ,  270   1  and  270   N ) is securely coupled to the server rack  100 . The power supply modules (e.g.  120   1 ,  120   2 ,  120   M+1 ) are coupled to horizontal busses (e.g.  260   1 ,  260   2 ,  260   3 ,  260   4 ,  260   M  and  260   M+1 ) as shown. Busses ( 260   1 ,  260   2 ,  260   3 ,  260   4 ,  260   M  and  260   M+1 ) are securely coupled to vertical bus bars ( 250   1 ,  250   2 ) as shown. Vertical bus bars ( 250   1  and  250   2 ) are also coupled to busses ( 270   1 ,  270   2  and  270   N ) and to the servers ( 130   1 ,  130   2 ,  130   N ). In an implementation, power cables are used in place of bus bars ( 250   1 ,  250   2 ). In this disclosure, bus bars can be replaced with less rigid busses; for example, busses made of short lengths of cables having lugs and/or locations for forming bolted interconnections. As shown, power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) are coupled to distribution busses (e.g.  260   1 ,  260   2 ,  260   3 ,  260   4 ,  260   M+1 ). 
     The server rack architecture of  FIG. 2  provides an uniform distribution of current along the various power distribution busses (including e.g.  250   1 ,  250   2 ). Uniform current distribution results from placing the power supply modules ( 120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ) near the loads (e.g.  130   1 ,  130   2 ,  130   N ). Lower current density results from supplying each load (e.g.  130   1 ) with the current from one or two power supply modules (e.g.  120   1  and  120   2 ) through their respective busses (e.g.  250   1 ,  250   2 ,  260   1 ,  260   2  and  270   1 ). As a result, the busses (including e.g.  250   1 ,  250   2 ,  260   1 ,  260   2  and  270   1 ) can be a of smaller size to accommodate this uniform and lower distribution of current density. Conventional server rack designs have the current concentrated at the top or at the bottom of the server rack. As such, all of the current used by the loads in the rack flows through a single point, and is then distributed along the rack. Conventional architecture requires the bus to be sized for the largest current load. The subject disclosure allows for smaller bus sizes, which results in reduced material costs. Another benefit of using the server rack architecture shown in  FIG. 2  is the improved isolation of component failures. For example, having multiple power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M , and  120   M+1 ) and common connecting busses (e.g.  250   1  and  250   2 ) provide redundancy that prevents failure of the entire rack  100  upon failure of an individual component. This reduces the size of the effect of certain catastrophic failures on the rack. For example, if one power supply (e.g.  120   1 ) was to fail, it would not cause the entire server rack to fail because the other power supplies (e.g.  120   3 ,  120   M ) in the rack would remain in operation. 
       FIG. 3  illustrates a rear view  300  of the power distribution components in an exemplary server rack having divided horizontal busses. As shown, the power supply modules (e.g.  120   1 ,  120   2 ,  120   3 ,  120   4 ,  120   M+1 ,  120   M+1 ) are coupled to busses (e.g.  360   1 ,  360   2 ,  360   3 , and  360   4 ,  360   M ,  360   M+1 ). Busses are coupled to the vertical bus bars  350   1  and  350   2  respectively. Vertical bus bar  350   1  is coupled to busses  370   1 ,  370   3 ,  370   M . Vertical bus bar  350   2  is coupled to busses  370   2 ,  370   4 ,  370   M+1 . Busses  370   1 ,  370   3 ,  370   M  are coupled to servers  330   1 ,  330   3 ,  330   N  respectively. Busses  370   2 ,  370   4 ,  370   M+1  are coupled to servers  330   2 ,  330   4 ,  330   M+1  respectively. Two servers (e.g.  330   1  and  330   2 ) are placed on top of a shelf (e.g.  110   1 ). Two servers (e.g.  330   3  and  330   4 ) are placed on top of another shelf (e.g.  110   2 ). The servers (e.g.  330   1  and  330   2 ) are placed generally equidistant from the center of the rack  100  towards the left and right posts ( 105   1  and  105   2 ). Each of the benefits of using the server rack architecture shown in  FIG. 1  and  FIG. 2  are common with the server architecture shown in  FIG. 3 . Furthermore, dividing the bus bars horizontally (e.g.  370   1 ,  370   2 ,  370   3 , and  370   4 ,  370   M ,  330   M+1 ) increases the isolation of failed load components. 
       FIG. 4  illustrates a rear view  400  of the power distribution components in an exemplary server rack having both vertically and horizontally divided busses. Vertical bus bars (e.g.  450   1  and  450   2 ) are located above vertical bus bars (e.g.  450   3  and  450   4 ) respectively. Eight (8) power supply modules ( 120   1 ,  120   2 ,  120   3 ,  120   4  and  420   1 ,  420   2 ,  420   3 ,  420   4 ) are coupled to eight horizontal busses ( 360   1 ,  360   2 ,  360   3 ,  360   4  and  460   1 ,  460   2 ,  460   3 ,  460   4 ) respectively. As shown, busses  360   1 ,  360   2 ,  360   3 , and  360   4  are coupled to vertical bus bars  450   1  and  450   2 . Also, as shown, busses  460   1 ,  460   2 ,  460   3 ,  460   4  are coupled to vertical bus bars  450   3  and  450   4 . Vertical bus bars  450   1  and  450   2  are coupled to busses  370   1 ,  370   2 ,  370   3 ,  370   4 . Vertical bus bars  450   3  and  450   4  are coupled to busses  470   1 ,  470   2 ,  470   3 ,  470   4 . Busses  370   1 ,  370   2 ,  370   3 ,  370   4 , are coupled to servers  330   1 ,  330   2 ,  330   3 ,  330   4 . Busses  470   1 ,  470   2 ,  470   3 ,  470   4  are coupled to servers  430   1 ,  430   2 ,  430   3 ,  430   4 . Each of the benefits of using the server rack architecture shown in  FIG. 3  is common to the server architecture shown in  FIG. 4 . Furthermore, dividing the bus bars both horizontally and vertically further increases the isolation of failed load components. 
       FIG. 5  illustrates a rear view  500  of an exemplary server rack having a central vertical power distribution bus. An array of electrical distribution busses (e.g.  550   1 ,  560   1 ,  560   2 ,  570   1 ,  570   2 ) is securely coupled to the server rack  100  shown in  FIG. 1  and is located at the rear side of the server rack. Two power supply modules  120   1  and  120   2  are coupled to the buss  560   1 . Two power supply modules  120   3  and  120   4  are coupled to the buss  560   2 . Busses (e.g.  560   1 ,  560   2 ) are coupled to vertical bus bar (e.g.  550   1 ). A central vertical distribution bus (e.g.  550   1 ) is generally located centered between the first and second sides. Vertical bus bar (e.g.  550   1 ) is coupled to horizontal busses (e.g.  570   1  and  570   2 ). Bus  570   1  is coupled to server  530   1 . Bus  570   2  is coupled to server  530   2 . The two servers  530   1  and  530   2  are placed on top of the shelves  510   1  and  510   2  respectively. The servers are placed generally centered, equidistant from the first and second sides. Each of the benefits of using the server rack architecture shown in  FIG. 2  is common with the server architecture shown in  FIG. 5 . However, the architecture shown in  FIG. 5  utilizes less bus materials by having the single vertical bus. 
       FIG. 6  illustrates a rear view  600  of an exemplary server rack demonstrating architecture including multiple, central, vertical distribution busses (e.g.  550   1 ,  650   2 ). Viewed from the back side of the server rack  100 , an array of electrical distribution busses (e.g.  550   1 ,  650   2 ,  560   1 ,  560   2 ,  570   1 ,  570   2 ,  660   1 ,  660   2 ,  670   1 ,  670   2 ) is securely coupled to the server rack  100  at the rear side of the server rack. Four (4) power supply modules  120   1 ,  120   2 ,  120   3 ,  120   4  are coupled to horizontal busses  560   1 ,  560   2 . Four (4) power supply modules  620   1 ,  620   2 ,  620   3 ,  620   4  are coupled to horizontal busses  660   1 ,  660   2 . Busses  560   1 ,  560   2  are coupled to vertical bus bar  550   1 . Busses  660   1 ,  660   2  are coupled to vertical bus bar  650   1 . Vertical bus bars ( 550   1 ,  650   1 ) are generally located centered between the first and second sides. The first vertical bus bar ( 550   1 ) is located above second vertical bus bar (e.g.  650   2 ). Vertical bus bars  650   1 ,  650   2  are also coupled to horizontal busses (e.g.  570   1 ,  570   2 ,  670   1 ,  670   2 ). Busses  570   1 ,  570   2 ,  670   1 ,  670   2  are coupled to servers (e.g.  130   1 ,  130   2 ,  630   1 ,  630   2 ). Four (4) servers (e.g.  130   1 ,  130   2 ,  630   1 ,  630   2 ) are placed on top of shelves (e.g.  510   1 ,  510   2 ,  610   1 ,  610   2 ). The servers are placed generally centered, equidistant from the first and second sides. Each of the benefits of using the server rack architecture shown in  FIG. 5  is common with the server architecture shown in  FIG. 6 . Furthermore, the architecture shown in  FIG. 6  provides for additional component isolation by dividing the vertical bus. 
       FIG. 7  illustrates an exemplary graphical representation  700  of a power supply unit. In an implementation, each power supply module  710   N  includes a battery  725   N  (or another type of energy storage device that can be used as a backup power source) and a power converter with uninterruptable power supply  720   N . Each battery  725   N  is removably coupled to a power converter  720   N . The battery  725   N  is accessible from the front side of the server rack  100  and can be removed from the front side of the server rack  100 . Removable coupling of the battery  725   N  includes mechanical and electrical coupling. 
     In an implementation, the power supply module  710   N  receives AC input from an AC source  735  through distribution lines  730   N . The power supply module  710   N  provides AC or DC output through distribution lines  740   N . In another implementation, the power supply module  710   N  receives DC input from a DC source  735  through distribution lines  730   N . The power supply module  710   N  provides AC or DC output through distribution lines  740   N . Output distribution lines  740   N  include busses and bus bars. Furthermore, each power supply module  710   N  sends and receives digital communication through communication lines  750   N  from a controller  770 . In various implementations power inputs and outputs are all AC, or all DC, or a combination thereof. It is to be understood that any combination of electrical inputs and outputs can be used with the server rack architecture  100  and with the power supply modules outlined herein. The power lines  730   N  and  740   N  and the communication lines  750   N  can be implemented by using a power strip  780 . The power strip  780  can be vertically secured to the back of the server  100 . The power strip  780  distributes both AC and DC power and also facilitates communication between the host  770  and the PSUs (e.g.  710   N ). 
     One of the benefits of the power supply module shown in  FIG. 7  is improved serviceability. By locating the battery  725   N  in front of the power converter  720   N , the battery  725   N  is made more accessible from the front of the server rack  100 . By having a removable connector between the battery  725   N  and the power converter  720   N , the battery  725   N  can be hot swapped. By having the AC  730   N , DC  740   N  and digital communication lines connected to the power supply module  710   N  from the back side of the server  100 , the serviceability of the module  710   N  is made easier. Furthermore, having the AC  730   N , DC  740   N  and digital communication lines coupled to the power supply module  710   N  from the back side of the rack  100  facilitates the use of the bus components and server rack architecture described herein. 
       FIG. 8  illustrates an exemplary isometric graphical representation  800  of a PSU tray and a server rack. In an implementation, the PSU tray  810   N  includes four vertically oriented sides and a bottom. Each of the four vertical sides is coupled to one another at two edges. Each of the four vertical sides is coupled to the edges of the bottom. In nonlimiting implementations, the sides and bottom can be coupled permanently, removably, or hinged as mentioned in this description. The walls and bottom can be of rigid or flexible materials. The walls can be of any shape. In one implementation, the vertical walls are shaped with cutouts to accommodate manipulation of the power supply module. In an implementation, the tray  810   N  includes details that allow users to grasp the tray from the front of the server rack  100  and remove the tray and a power supply module (e.g.  120   1 ). Nonlimiting examples of these details are handles, knobs or hooks. The details can be mounted to the top, front, first side or second side of the trays. In an implementation, a side is located at the rear of the tray. This rear side may be of any height. In an implementation, removable coupling of the batteries includes the use of a tray  810   N  having interior dimensions such that a power converter  720  and a battery  725  would fit with minimal clearance and be mechanically retained by any two opposing sides of the tray. It is to be understood that the battery  725  is only one type of backup power source that can be used. Other types of energy storage devices can be used as backup power sources. 
       FIG. 9  illustrates a flow diagram of an exemplary method for assembling a server rack. According to the methodology shown in the flow diagram  900 , at  910 , shelves (such as  110   1 ,  110   2 , and  110   N  as shown in  FIG. 1 ) are stacked vertically to form the rack. At  920 , a first server (such as  130   1  as shown in  FIG. 1 ) is located between the first and second power supply modules (such as  120   1  and  120   2  as shown in  FIG. 1 ) on a first shelf (such as  110   1  as shown in  FIG. 1 ). At  930 , a second server (such as  130   2  as shown in  FIG. 1 ) is located between the third and fourth power supply modules (such as  120   3 ,  120   4  as shown in  FIG. 1 ) on a second shelf (such as  110   2  as shown in  FIG. 1 ). 
     At  940 , a first bus bar (such as vertical bus  250   1  as shown in  FIG. 2 ) is connected to first and third power supply modules (such as  120   1  and  120   3  as shown in  FIG. 2 ). At  950 , a second bus bar (such as vertical bus  250   2  as shown in  FIG. 2 ) is connected to second and fourth power supply modules (such as  120   2  and  120   4  as shown in  FIG. 2 ). At  960 , the first bus bar (such as vertical bus  250   1  as shown in  FIG. 2 ) is connected to a first server (such as  130   1  as shown in  FIG. 2 ) to supply voltage and current to the first server. At  970 , the second bus (such as vertical bus  250   2 ) is coupled to a second server (such as  130   2  as shown in  FIG. 2 ) to supply voltage and current to the second server. 
     A benefit of using the method of server rack assembly  900  is the resulting more uniform distribution of lower current density along the various power distribution busses (such as  250   1 ,  260   M  and  270   M  shown in  FIG. 2 ). Uniform current distribution results from placing the power supply modules (such as  120   N  shown in  FIG. 2 ) near the loads e.g.  130   N  shown in  FIG. 1 ). Lower current results from supplying each load (such as  130   N  shown in  FIG. 2 ) with the current from one or two power supply modules (such as  120   N  shown in  FIG. 2 ) through their respective busses (such as  250   1 ,  250   2 ,  260   N+1  and  270   M  shown in  FIG. 2 ). Busses (such as  250   1 ,  260   M  and  270   N  shown in  FIG. 2 ) can be a smaller size and adequately accommodate this uniform distribution of lower current density. Another benefit of using the method of assembling server rack architecture shown in  FIG. 9  is the improved accessibility to the power supply modules (e.g.  120   1 thru M+1  shown in  FIG. 2 ). Being located to the first and second sides and distributed vertically, the power supply modules ( 120   1 thru M+1 ) are accessible from the front side of the server rack  100  shown in  FIG. 1 . Another benefit of the method of assembling a server rack shown in  FIG. 9  is that multiple power supply modules (e.g.  120   1,2,3  shown in  FIG. 2 ) are attached to the common bus bars  250   1  and  250   2  and the servers (e.g.  130   N ) shown in  FIG. 2 . This provides for a redundancy of power. It is to be understood that the rack can be placed or positioned inside a computer system, a device or a server room vertically, horizontally or at an angle. It is to be understood that if the rack is positioned horizontally or at an angle, the devices on the rack must be secured to the shelves such that they don&#39;t slide or fall off the rack because of gravity. It is also to be understood that the various shelves and busses of the server rack can be positioned at different angles. 
       FIG. 10  illustrates an example methodology for hot swapping a server rack component. According to the construction methodology flow diagram  1000 , at  1010 , a component requiring service is identified. Service as used herein can include, for example, repair, replacement or inspection. At  1020 , the component requiring service is removed from the rack. To that end, the component requiring service is turned off and no other components in the rack are turned off. Turning off includes, for example, pushing buttons or sending control signals that deactivate the operations of the component. The primary advantage of hot swapping is that a component is removed and replaced from a system of components without affecting the operation of the other components. The server rack system  100  as discussed herein facilitates hot swapping PDUs (e.g.  140   1  shown in  FIG. 1 ) power supply modules (e.g.  120   N  shown in  FIG. 1 ) and servers (e.g.  130   N  shown in  FIG. 1 ). It is to be understood that other components can be added to the server rack  100  and can be hot swappable. The component requiring service is also mechanically disconnected from the rack. Mechanical disconnection includes the disassembly of any of the mechanical couplings discussed herein. Prior to or after mechanically disconnecting the component, the component requiring service is electrically disconnected from the rack. Electrical disconnection includes disassembly of any of the electrical couplings discussed herein. At  1030 , a new, repaired or replacing component is electrically, mechanically and/or programmatically connected to the rack. Mechanical reconnection includes returning the component to its shelf, tray or otherwise placed into the rack. At  1040 , the component is turned on and its operation commences. 
       FIG. 11  illustrates an exemplary graphical representation  1100  of a server rack with removable PSUs racks. A server component rack  1104  is supported by four corner posts or two sides, vertically oriented to define four sides including a front, a back and two additional sides. The server component rack  1104  houses and physically supports load components (e.g.  1130   N ,  1133   N  and  1136   N ). A PSUs rack  1108  is also shown that houses and physically supports PSUs and related components (e.g.  1140   N  (e.g. a PDU),  1150   N  (e.g. a bus)  1120   N , (e.g. a PSU)). Additionally, the PSUs rack (or power components rack)  1108  has multiple wheels or casters  1180 . The wheels  1180  facilitate the movement of the power component rack  1108  independently of server component rack  1104 . 
     The PDU  1140   N  receives external AC (or DC) voltage and current, and controls the flow of the input current (e.g. by using fuses or circuit breakers). Power control modules  1140   N  are connected to power supply modules  1120   N . Bus bars  1160   N  are coupled to power supply modules  1120   N  and vertical bus bars  1150   N . Bus bars  1170   N  are coupled to vertical bus bar  1150   N  and loads (e.g.  1130   N ,  1133   N  and  1136   N ). In an implementation, bus bars  1170   N  are securely coupled to vertical bus bars  1150   N  and removably coupled to the loads (e.g.  1130   N ,  1133   N  and  1136   N ) such that bus bars  1170   N  generally travel as parts of the power component rack  1108 . In an implementation, bus bars  1175   N  are securely coupled to the loads (e.g.  1130   N ,  1133   N  and  1136   N ) and removably coupled to the vertical bus bars  1150   N  such that the bus bars  1175   N  generally travel with the loads. 
     The advantages of the implementation of the server rack  1104  and separate power rack  1108  assembly  1100  (assembly) are common with those outlined herein for various implementations. One additional advantage of the assembly  1100  is the mobility of power component racks  1108 . For example, when loads on a server rack  1104  require low current, only one power component rack  1108  may be necessary. The additional power component rack  1108  can be disconnected mechanically and electrically from the server component rack  1104  in a first location, and moved to a second location. Such mobility can free space in the first location. Another advantage of such mobility is the opportunity for servicing the battery rack in the second location. 
     What has been described above includes examples of the implementations. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the claimed subject matter, but it is to be appreciated that many further combinations and permutations of the subject innovation are possible. Accordingly, the claimed subject matter is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims. Moreover, the above description of illustrated implementations of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed implementations to the precise forms disclosed. While specific implementations and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such implementations and examples, as those skilled in the relevant art can recognize.