Abstract:
An uninterruptible power supply (UPS) apparatus is disclosed that can receive power from different electrical utility configurations. The input stage of the UPS includes a three phase rectifier bridge design having three legs configured for connection to the different electrical utility configurations. An advantage that may be realized in the practice of some disclosed embodiments of the UPS input stage is that a single UPS can have the flexibility to be used with different electrical utility configurations having different voltages and phases.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to an uninterruptible power supply (UPS), and in particular, a UPS input stage that can receive power from different electrical utility configurations. 
         [0002]    Uninterruptible Power Supplies are used to provide clean power to critical loads (e.g., protected equipment such as computers, data centers, cash registers) even if the input power source fails. A UPS can provide instantaneous protection from input power source interruptions by supplying energy stored in batteries or other capacitive devices that can power the protected equipment for a sufficient amount of time to start a backup power source or properly shut down the protected equipment. Since critical loads can be found in a variety of residential or commercial locations having different electrical utility configurations (e.g., different alternating current (AC) voltages (120V, 208V, 240V) and/or different number of phases (1 or 2) with different phase angles (120°, 180°, or 240°). Different UPS&#39;s have to be designed for connecting to the different electrical utility configurations. 
         [0003]      FIG. 1  is a schematic diagram of an illustrative and exemplary electrical utility configuration  2 , having a first voltage source  10  with a first voltage source line (LINE  1 )  11 , a second voltage source  20  with a second voltage source line (LINE  2 )  21 , a neutral node (or center tap)  40  with a neutral  41  located between and connecting the first voltage source  10  and the second voltage source  20 . The exemplary electrical utility configuration  2  can be representative of a conventional single phase three-wire electrical utility configuration also referred to as a split-phase system or a center-tapped neutral system, since it can be formed by, e.g., center-tapping the secondary winding of a transformer (or generator/alternator) to form a first voltage source  10  and a second voltage source  20 . The exemplary service can be representative of two phases of a three-phase four-wire wye electrical utility configuration or two phases of a three-phase three-wire delta electrical utility configuration. 
         [0004]    In one example, a first single phase input voltage (V 1 ) between the first voltage source line (LINE  1 )  11  and the neutral node  40  is 120VAC at a phase angle of 0°, while the second single phase input voltage (V 2 ) between the second voltage source line (LINE  2 )  21  and the neutral node  40  is 120VAC at a phase angle of 180°. Without connecting the neutral  41 , the single phase input voltage (V 3 ) between the first voltage source line (LINE  1 )  11  and the second voltage source line (LINE  2 )  21  is 240VAC. By connecting the neutral  41 , a split phase input voltage can be provided with a phase difference of 180° between the two voltage sources  10 ,  20 . 
         [0005]    In another example, the first single phase input voltage (V 1 ) between the first voltage source line (LINE  1 )  11  and the neutral node  40  is 120VAC at a phase angle of 0°, while the second single phase input voltage (V 2 ) between the second voltage source line (LINE  2 )  21  and neutral  40  is 120VAC at a phase angle of 120° or 240°. Without connecting the neutral  41 , the single phase input voltage (V 3 ) between the first voltage source line (LINE  1 )  11  and the second voltage source line (LINE  2 )  21  is 208VAC. By connecting the neutral  41 , a split phase input voltage can be provided with a phase difference of 120° or 240° between the two voltage sources  10 ,  20 . 
         [0006]    The design of a UPS for a single phase input voltage of 120VAC will be different than the design of a UPS for a single phase input voltage of 208VAC or 240VAC. Similarly, the design of a UPS for a single phase input voltage will be different than the design of a UPS for a split phase input voltage. In addition, since some electrical utility configurations do not have a neutral (e.g., 208VAC or 240VAC single phase) while other electrical utility configurations do have a neutral (e.g., 120VAC single phase), different UPS designs must be provided for these different electrical utility configurations. The requirement for different UPS designs for all of the different possible electrical utility configurations limits the flexibility of the use of the UPS&#39;s to protect equipment. For example, a company with locations in areas having different electrical utility configurations would need to purchase and stock a number of different types of UPS to protect its equipment in the different locations where it has operations. 
         [0007]    The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    An uninterruptible power supply (UPS) apparatus is disclosed that can receive power from different electrical utility configurations. The input stage of the UPS includes a three phase rectifier bridge design having three legs configured for connection to the different electrical utility configurations. An advantage that may be realized in the practice of some disclosed embodiments of the UPS input stage is that a single UPS can have the flexibility to be used with different electrical utility configurations having different voltages and phases. 
         [0009]    In one embodiment, a UPS apparatus for receiving power from different electrical utility configurations. The apparatus comprises a three phase rectifier bridge comprising a first leg comprising a first rectifier diode and a second rectifier diode with a first leg node located between and connecting the first and second rectifier diodes, a second leg comprising a third rectifier diode and a fourth rectifier diode with a second leg node located between and connecting the third and fourth rectifier diodes, and a third leg comprising a fifth rectifier diode and a sixth rectifier diode with a third leg node located between and connecting the fifth and sixth rectifier diodes, wherein the first leg, the second leg, and the third leg are connected in parallel; a switch connected in parallel with the three phase rectifier bridge; a direct current output circuit connected in parallel with the three phase rectifier bridge and the switch, the direct current output circuit comprising a first output bus and a second output bus with an output bus ground node located between and connecting the first output bus and the second output bus; a first UPS input connected to the second leg node of the three phase rectifier bridge with a first input filter inductor located between and connecting the first UPS input to the second leg node; and a second UPS input connected to the third leg node of the three phase rectifier bridge with a second input filter inductor located between and connecting the second UPS input to the third leg node; and a third UPS input connected to the output bus ground node. 
         [0010]    In another embodiment, the UPS apparatus further comprises a power distribution unit (PDU) for providing an interface for connecting the different electrical utility configurations to the UPS, the power distribution unit comprising a first PDU output connected to the first UPS input, a second PDU output connected to the second UPS input, and a third PDU output connected to the third UPS input. 
         [0011]    This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
           [0013]      FIG. 1  is a schematic diagram of an exemplary electrical utility configuration; 
           [0014]      FIG. 2  is a schematic diagram of an exemplary input stage of an uninterruptible power supply (UPS); 
           [0015]      FIG. 3  is a schematic diagram of the exemplary input stage of a UPS of  FIG. 2  with a power distribution unit (PDU); 
           [0016]      FIG. 4  is a schematic diagram of the exemplary UPS input stage of  FIG. 3  connected to the exemplary electrical utility configuration of  FIG. 1  with the neutral connected to the UPS for a two-wire 120VAC single phase input voltage; 
           [0017]      FIG. 5  is a schematic diagram of the exemplary UPS input stage of  FIG. 3  connected to the exemplary electrical utility configuration of  FIG. 1  without a neutral connected to the UPS for a two-wire 208VAC/240VAC single phase input voltage; and 
           [0018]      FIG. 6  is a schematic diagram of the exemplary UPS input stage of  FIG. 3  connected to the exemplary electrical utility configuration of  FIG. 1  with a neutral connected to the UPS for a three-wire 208VAC/240VACsplit phase input voltage. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 2  is a schematic diagram of an exemplary input stage  100  of a uninterruptible power supply (UPS) for receiving power from different electrical utility configurations from, e.g., the exemplary electrical utility configuration  2  of  FIG. 1 . As explained, the exemplary electrical utility configuration  2  can provide several different electrical utility configurations to the UPS input stage  100 , including single phase input voltages (V 1 =120VAC, V 3 =208VAC/240VAC) and split phase input voltages (with phase angles between the first voltage source  10  and the second voltage source  20  of 120°, 180°, or 240°). 
         [0020]    The UPS input stage  100  includes a three phase rectifier bridge  140  having a first leg  110 , a second leg  120 , and a third leg  130  connected in parallel. The first leg  110  includes a first rectifier diode (D 1 )  111  and a second rectifier diode (D 2 )  112  with a first leg node  113  located between and connecting the two diodes  111 ,  112 . The second leg  120  includes a third rectifier diode (D 3 )  121  and a fourth rectifier diode (D 4 )  122  with a second leg node  123  located between and connecting the two diodes  121 ,  122 . The third leg  130  includes a fifth rectifier diode (D 5 )  131  and a sixth rectifier diode (D 6 )  132  with a third leg node  133  located between and connecting the two diodes  131 ,  132 . It will be understood that the term “connecting” as used herein includes indirectly and directly connecting (i.e., two components are connected to each other even if there are additional components in between). 
         [0021]    In one embodiment, the UPS input stage  100  further includes a switch  150  connected in parallel with the three phase rectifier bridge  140 . In one embodiment, the switch  150  can comprise one or more insulated gate bipolar transistors (IGBT&#39;s), while in another embodiment, the switch can comprise one or more metal-oxide-semiconductor field-effect transistor (MOSFET&#39;s). Conventional strategies for modulating the switch  150  can be used to control the operation of the three phase rectifier bridge  140 . 
         [0022]    In one embodiment, the UPS input stage  100  further includes an direct current (DC) output circuit  180  connected in parallel with the three phase rectifier bridge  140  and the switch  150 . The DC output circuit  180  comprises a first output bus capacitor (C 1 )  161  (e.g., 4000 g) and a second output bus capacitor (C 2 )  162  (e.g., 4000 g). An output bus ground node  193  is located between and connects the first output bus capacitor  161  and the second output bus capacitor  162 . The output bus ground node  193  is connected to ground  170 . The DC output circuit  180  also comprises a seventh rectifier diode (D 7 )  151  located between and connecting the switch  150  and the first output bus capacitor  161 , with the anode connected to the switch  150  and the cathode connected to the first output bus capacitor  161 . Similarly, the DC output circuit  180  comprises an eighth rectifier diode (D 8 )  152  located between and connecting the switch  150  and the second output bus capacitor  162 , with the cathode connected to the switch  150  and the anode connected to the second output bus capacitor  162 . 
         [0023]    In one embodiment, the UPS input stage  100  has four inputs  101 ,  102 ,  103 ,  104 . A first UPS input  101  is configured for connecting to the first voltage source line (LINE 1 )  11  ( FIG. 1 ) and is connected via a first input filter inductor (L 1 )  141  (e.g., 1.0 mH) to the second leg node  123  of the three phase rectifier bridge  140 . A second UPS input  102  is configured for connecting to the second voltage source line (LINE 2 )  21  ( FIG. 1 ) and is connected via a second input filter inductor (L 2 )  142  (e.g., 1.0 mH) to the third leg node  133  of the three phase rectifier bridge  140 . A third UPS input  103  is configured for connecting to the neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) and is connected to the output bus ground node  193 , which is connected to ground  170 . A fourth UPS input  104  is configured for connecting to the neutral node (or center tap)  40  neutral  41  of the electrical utility configuration  2  for a 120VAC single phase input voltage (V 1 ) ( FIG. 1 ) and is connected to the first leg node  113  of the three phase rectifier bridge  140 . 
         [0024]    The UPS input stage  100  has a first UPS output  191  taken across the first output bus capacitor (C 1 )  161  to ground  170 , which provides a positive DC output voltage (e.g., +220VDC). The UPS input stage  100  also has a second UPS output  192  taken across the second output bus capacitor (C 2 )  162  to ground  170 , which provides a negative DC output voltage (e.g., −220VDC). The UPS input stage  100  illustrated in  FIG. 1  is designed to provide approximately the same first UPS output  191  (e.g., +220VDC) and second UPS output  192  (e.g., −220VDC) for different electrical utility configurations. 
         [0025]      FIG. 3  is a schematic diagram of the exemplary UPS input stage  100  of  FIG. 2  with a power distribution unit (PDU)  200 , which is configured for providing an interface for connecting different electrical utility configurations to the UPS input stage  100 . It will be understood that the PDU  200  can be provided as a separate unit or can be integrated as part of the UPS input stage  100 . In one embodiment, the PDU  200  has three inputs  201 ,  202 ,  203 . A first PDU input  201  is configured for connecting to the first voltage source line (LINE 1 )  11  ( FIG. 1 ). A second PDU input  202  is configured for connecting to the second voltage source line (LINE 2 )  21  ( FIG. 1 ). A third PDU input  203  is configured for connecting to the neutral node (or center tap)  40  via the neutral  41  of the electrical utility configuration  2  ( FIG. 1 ). 
         [0026]    In one embodiment, the PDU  200  has four outputs for connecting to the inputs  101 ,  102 ,  103 ,  104  of the UPS input stage  100 . For example, a first PDU output  211  is configured for connecting to the first UPS input  101  (which is configured for connecting to the first voltage source line (LINE 1 )  11  ( FIG. 1 )). A second PDU output  212  is configured for connecting to the second UPS input  102  (which is configured for connecting to the second voltage source line (LINE 2 )  21  ( FIG. 1 )). A third PDU output  213  is configured for connecting to the third UPS input  103  (which is configured for connecting to the neutral  41  of the electrical utility configuration  2  ( FIG. 1 )). A fourth PDU output is configured for connecting to the fourth UPS input  104  (which is configured for connecting for connecting to the neutral  41  of the electrical utility configuration  2  for a two-wire 120VAC single phase input voltage (V 1 ) ( FIG. 4 )). 
         [0027]      FIG. 4  is a schematic diagram of the exemplary UPS input stage  100  of  FIG. 3  connected to the exemplary electrical utility configuration  2  of  FIG. 1  with the neutral  41  connected to the UPS input stage  100  for a two-wire 120VAC single phase input voltage (V 1 =120VAC at a phase angle of 0°). The configuration of  FIG. 4  for the two-wire 120VAC single phase input voltage will provide a positive DC output voltage (e.g., of approximately +220VDC) at the first UPS output  191  and a negative DC output voltage (e.g., of approximately −220VDC) at the second UPS output  192 . 
         [0028]    The first voltage source line (LINE  1 )  11  is connected to both the first UPS input  101  (which is connected to the second leg node  123  of the three phase rectifier bridge  140 ) and the second UPS input  102  (which is connected to the third leg node  133  of the three phase rectifier bridge  140 ). The neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) is connected to both the third UPS input  103  (which is connected to the output bus ground node  193 ) and the fourth UPS input  104  (which is connected to the first leg node  113  of the three phase rectifier bridge  140 ). In one embodiment, the neutral node  40  and the neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) are connected to ground. Since the first input filter inductor (L 1 )  141  is connected in parallel with the second input filter inductor (L 2 )  142 , current through each of the input filter inductors  141 ,  142  at this lower input voltage (120VAC) is halved (i.e., similar to the current for a higher input voltage of 240VAC) allowing for the use of smaller sized input filter inductors  141 ,  142  (e.g., 1.0 mH). 
         [0029]    In one embodiment, the connections between the first voltage source  10  and the UPS input stage  100  can be made directly, while in another embodiment as shown in  FIG. 4 , the PDU  200  can be employed to provide an interface between the first voltage source  10  and the UPS input stage  100  inputs  101 ,  102 ,  103 ,  104 . The first voltage source line (LINE  1 )  11  is connected to the first PDU input  201 , which is connected through the PDU  200  to the first PDU output  211 , which can then be connected to the first UPS input  101 . A first PDU node  215  within the PDU  200  also connects the first PDU input  201 , which is connected to the first voltage source line (LINE  1 )  11 , to the second PDU output  212 , which can then be connected to the second UPS input  102 . Similarly, the neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) is connected to the third PDU input  203 , which is connected through the PDU  200  to the third PDU output  213 , which can then be connected to the third UPS input  103 . A second PDU node  216  within the PDU  200  also connects the third PDU input  203 , which is connected to the neutral  41  of the electrical utility configuration  2  ( FIG. 1 ), to the fourth PDU output  214 , which can then be connected to the fourth UPS input  104 . 
         [0030]      FIG. 5  is a schematic diagram of the exemplary UPS input stage  100  of  FIG. 3  connected to the exemplary electrical utility configuration  2  of  FIG. 1  without a neutral  41  connected to the UPS input stage  100  for a two-wire 208VAC/240VAC single phase input voltage (V 3 =208/240VAC). The configuration of  FIG. 5  for the two-wire 208VAC/240VAC single phase input voltage will provide a positive DC output voltage (e.g., of approximately +220VDC) at the first UPS output  191  and a negative DC output voltage (e.g., of approximately −220VDC) at the second UPS output  192 . 
         [0031]    The first voltage source line (LINE  1 )  11  is connected to the first UPS input  101  (which is connected to the second leg node  123  of the three phase rectifier bridge  140 ). The second voltage source line (LINE 2 )  21  is connected to the second UPS input  102  (which is connected to the third leg node  133  of the three phase rectifier bridge  140 ). There is no connection to the third UPS input  103  or the fourth UPS input  104  since the neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) is not connected. Although the first input filter inductor (L 1 )  141  is connected in series with the second input filter inductor (L 2 )  142 , the current is limited through each of the input filter inductors  141 ,  142  at this higher input voltage (208VAC/240VAC), allowing for the use of smaller sized input filter inductors  141 ,  142  (e.g., 1.0 mH). 
         [0032]    In one embodiment, the connections between the first and second voltage sources  10 ,  20  and the UPS input stage  100  can be made directly, while in another embodiment as shown in  FIG. 5 , the PDU  200  can be employed to provide an interface between the first and second voltage sources  10 ,  20  and the UPS input stage  100  inputs  101 ,  102 . The first voltage source line (LINE  1 )  11  is connected to the first PDU input  201 , which is connected through the PDU  200  to the first PDU output  211 , which can then be connected to the first UPS input  101 . Similarly, the second voltage source line (LINE 2 )  21  is connected to the second PDU input  202 , which is connected through the PDU  200  to the second PDU output  212 , which can then be connected to the second UPS input  102 . 
         [0033]      FIG. 6  is a schematic diagram of the exemplary UPS input stage  100  of  FIG. 3  connected to the exemplary electrical utility configuration  2  of  FIG. 1  with a neutral  41  connected to the UPS input stage  100  for a three-wire 120VAC split phase input voltage (V 1,2 =120VAC at a phase angle of 180° resulting in V 3 =240VAC or V 1,2 =120VAC at a phase angle of 120° resulting in V 3 =208VAC). The configuration of  FIG. 6  for the three-wire split phase input voltage will provide a positive DC output voltage (e.g., of approximately +220VDC) at the first UPS output  191  and a negative DC output voltage (e.g., of approximately −220VDC) at the second UPS output  192 . 
         [0034]    The first voltage source line (LINE  1 )  11  is connected to the first UPS input  101  (which is connected to the second leg node  123  of the three phase rectifier bridge  140 ). The second voltage source line (LINE 2 )  21  is connected to the second UPS input  102  (which is connected to the third leg node  133  of the three phase rectifier bridge  140 ). The neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) is connected to the third UPS input  103  (which is connected to the output bus ground node  193 ). 
         [0035]    In one embodiment, the connections between the first and second voltage sources  10 ,  20  and the UPS input stage  100  can be made directly, while in another embodiment as shown in  FIG. 6 , the PDU  200  can be employed to provide an interface between the first and second voltage sources  10 ,  20  and the UPS input stage  100  inputs  101 ,  102 . The first voltage source line (LINE  1 )  11  is connected to the first PDU input  201 , which is connected through the PDU  200  to the first PDU output  211 , which can then be connected to the first UPS input  101 . Similarly, the second voltage source line (LINE 2 )  21  is connected to the second PDU input  202 , which is connected through the PDU  200  to the second PDU output  212 , which can then be connected to the second UPS input  102 . The neutral  41  of the electrical utility configuration  2  ( FIG. 1 ) is connected to the third PDU input  203 , which is connected through the PDU  200  to the third PDU output  213 , which can then be connected to the third UPS input  103 . 
         [0036]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.