Abstract:
Air conditioning systems including a refrigeration circuit having at least one fan or blower are provided. The air conditioning systems also include a multi-voltage induction motor coupled to the fan/blower. The multi-voltage induction motor includes motor windings adapted for use when the motor windings are wired in a first voltage wiring configuration and a second voltage wiring configuration, the second voltage being greater than the first voltage. The multi-voltage induction motor may be wired in the first voltage wiring configuration, and a variable frequency drive may be adapted to maintain an operating voltage to frequency ratio of the multi-voltage induction motor at approximately a voltage to frequency design ratio of the multi-voltage induction motor. Also provided are power conductors adapted to transmit power to the variable frequency drive at a voltage approximately equal to the second voltage for operation of the multi-voltage induction motor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Non-Provisional patent application of U.S. Provisional Patent Application No. 61/232,258, entitled “Blower/Fan Over-Speed”, filed Aug. 7, 2009, which is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The invention relates generally to induction motors, and, more particularly, to multi-voltage induction motors for powering of fans and/or blowers. 
         [0003]    Induction motors are utilized in a variety of industries and applications, such as ground support equipment units that support grounded aircrafts. Such motors typically include stator windings in a core disposed around a rotor and capable of creating a rotating magnetic field that induces rotor rotation. As such, induction motors may not supply a current directly to the rotor to generate rotor rotation; power is supplied to the rotor via electromagnetic induction. The foregoing features of induction motors may offer advantages over synchronous motors, such as the absence of brushes, the ability to exhibit close control over the speed of the motor, and so forth. 
         [0004]    Unfortunately, while induction motors offer many advantages, such motors are also associated with drawbacks, which may inhibit or prevent their use in some applications. For example, induction motors apply torque based on a ratio of the voltage to the frequency and are typically associated with preset current and voltage ratings. Such features may limit the operational speed and power capabilities of induction motors, possibly resulting in the need for bulky system components, which may be heavy and costly. Further, induction motors sometimes may be configured to be wired either in a low voltage configuration and operated with a low voltage source or in a high voltage configuration and operated with a high voltage source. Such a feature may limit the power output achievable with the induction motor. Accordingly, there exists a need for systems and devices that address such drawbacks with current induction motor operation. 
       BRIEF DESCRIPTION 
       [0005]    In an exemplary embodiment, an air conditioning system includes a refrigeration circuit having at least one fan or blower. The air conditioning system also includes a multi-voltage induction motor coupled to the at least one fan or blower and including motor windings adapted for use when the motor windings are wired in a first voltage wiring configuration and a second voltage wiring configuration, the second voltage being greater than the first voltage. The multi-voltage induction motor is wired in the first voltage wiring configuration. The air conditioning system also includes a variable frequency drive coupled to the multi-voltage induction motor and adapted to maintain an operating voltage to frequency ratio of the multi-voltage induction motor at approximately a voltage to frequency design ratio of the multi-voltage induction motor. The air conditioning system also includes power conductors adapted to transmit power to the variable frequency drive at a voltage approximately equal to the second voltage for operation of the multi-voltage induction motor wired in the first voltage wiring configuration. 
         [0006]    In another embodiment, an air conditioning system includes a refrigeration circuit having at least one fan or blower. The air conditioning system also includes a three phase alternating current (AC) induction motor coupled to the at least one fan or blower and including windings adapted to be interconnected in a first voltage configuration and a second voltage configuration, the second voltage being greater than the first voltage, wherein the windings are interconnected in the first voltage configuration. The air conditioning system also includes three phase power conductors adapted to provide an output voltage equal to approximately the second voltage and a variable frequency drive adapted to receive power from the three phase power conductors and to control operation of the three phase AC induction motor. 
         [0007]    In another embodiment, an air conditioning system includes a refrigeration circuit having at least one fan or blower. The air conditioning system also includes a multi-voltage induction motor coupled to the at least one fan or blower and including windings adapted to be wired in a first voltage configuration and a second voltage configuration, the second voltage being greater than the first voltage, wherein the windings are wired in the first voltage configuration. The air conditioning system also includes a variable frequency drive coupled to the multi-voltage induction motor and adapted to increase an operating speed of the multi-voltage induction motor to a level exceeding a rated speed while maintaining a rated voltage to frequency ratio of the multi-voltage induction motor. The air conditioning system also includes power conductors adapted to provide the variable frequency drive an input voltage equal to approximately the second voltage for operation of the multi-voltage induction motor. 
     
    
     
       DRAWINGS 
         [0008]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0009]      FIG. 1  illustrates an aircraft coupled to an exemplary air delivery system including an oversped induction motor via an air hose assembly in accordance with aspects of the present invention; 
           [0010]      FIG. 2  is a schematic illustrating an exemplary refrigeration system including a variety of multi-voltage induction motors that may be utilized in the ground support equipment unit of  FIG. 1  in accordance with aspects of the present invention; 
           [0011]      FIG. 3  is a pressure-flow graph illustrating a duct system flow curve, a lower speed blower curve, and a higher speed blower curve in accordance with aspects of the present invention; and 
           [0012]      FIG. 4  is a graph illustrating exemplary plots of oversped torque, traditional torque, oversped horsepower, and traditional horsepower in accordance with aspects of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As described in detail below, embodiments are provided of multi-voltage induction motors wired in a lower voltage configuration but configured for operation at a higher supply voltage. As such, the multi-voltage induction motors described herein may be “oversped” for blower and fan operation via coupling of the multi-voltage induction motors to a variable frequency drive (VFD) configured to receive power from one or more power conductors. Overspeeding of the multi-voltage induction motors in this manner may facilitate the production of a higher power output from the blower or fan (for improved air displacement, efficiency, and cooling) as compared to a multi-voltage motor wired in the lower voltage configuration and configured for operation at a lower supply voltage. The foregoing feature may have the effect of reducing the size, weight, and expense of multi-voltage induction motors chosen for a variety of applications. For example, by overspeeding the multi-voltage induction motors associated with refrigeration cycles located on aircraft ground support equipment, the size and weight of such ground support equipment may be reduced compared to existing systems without compromising the desired output. However, although the multi-voltage induction motors shown herein are illustrated and discussed in the context of aircraft ground support equipment, it should be noted that embodiments of the oversped motors described herein may be used in any of a variety of contexts for any of a variety of suitable applications. 
         [0014]    Turning now to the drawings,  FIG. 1  illustrates a preconditioned air hose assembly  10  that is configured to couple an air delivery system  12  to an aircraft  14 . In the illustrated embodiment, the air hose assembly  10  includes a first connector  16 , which connects the air delivery system  12  to a hose portion  18  of the air hose assembly  10 . The illustrated air hose assembly  10  also includes a second connector  20 , which connects the aircraft  14  to the hose portion  18  of the air hose assembly  10 . The air hose assembly  10  delivers conditioned air to the aircraft  14  to alleviate the need to use the air conditioning system of the aircraft itself while the aircraft  14  is parked, or to supplement any on-board air conditioning that may be inadequate for the needed air conditioning when the aircraft is on the ground. As such, the conditioned air may be cooled air, heated air, filtered air, or air conditioned to any other suitable state. Such preconditioned air may be beneficial for temperature regulation of electronics and/or aircraft personnel while the aircraft  14  is on the ground. 
         [0015]    In the illustrated embodiment, the aircraft  14  is a high performance military aircraft  14 . However, in other embodiments, the aircraft  14  may be any aircraft, such as a commercial passenger airplane or a private aircraft. Furthermore, aircraft  14  is illustrated as it may be parked on the ground, such as at a terminal or other facility. The ground is generally a tarmac, runway, or hangar floor, but could be any surface on which an aircraft is parked (e.g., the deck or hold of a ship). The air hose assembly  10  is typically moved out of the way of the aircraft when the aircraft is in motion, such as when it taxies to and from a terminal. When aircraft  14  is parked, air hose assembly  10  is moved into proximity and connected to aircraft  14 , thus connecting the air delivery system  12  and aircraft  14 . Before aircraft  14  begins moving, air hose assembly  10  is detached from aircraft  14  and moved away so that it is not in the path of aircraft  14  or so that it can be used to couple air delivery system  12  to another aircraft. 
         [0016]    The air delivery system  12  may, for example, be a mobile ground support unit, as illustrated in  FIG. 1 . Alternatively, the air delivery system  12  may include equipment that is attached to a passenger bridge or to a fixed location, such as the terminal building. Furthermore, the air delivery system  12  may include one of more multi-voltage induction motors that are configured to be oversped during operation. That is, the air delivery system  12  may include induction motors used to power fans, blowers, and so forth, located within the air delivery system  12 . Such multi-voltage induction motors may be configured to be wired in at least two configurations, specifically, a first wiring configuration and a second wiring configuration, corresponding respectively to a first voltage and a second voltage higher than the first voltage. In accordance with the present techniques, at least one of the multi-voltage induction motors is wired in the first wiring configuration but operated with the second higher supply voltage. 
         [0017]    For example, in one embodiment, the multi-voltage induction motor may be configurable for 440V supplied to 220V wiring in the oversped configuration. Such an embodiment may increase the power capability of the induction motor as compared to an induction motor with 220V supplied to 220V wiring. The foregoing advantage may be achieved because the oversped induction motor may be associated with a variable frequency drive (VFD) that receives power from one or more power conductors and allows the frequency of the power supplied to the motor to be increased above or below the rated grid or power supply frequency (e.g., 60 Hz in North America), thereby regulating the voltage and facilitating proper motor function. 
         [0018]      FIG. 2  is a schematic illustrating an exemplary refrigeration system  22  including a variety of multi-voltage induction motors that may be utilized in the ground support equipment unit  12  of  FIG. 1 . Specifically, in the embodiment shown, the refrigeration system  22  utilizes a vapor-compression cycle to generate the conditioned air. However, it should be noted that the refrigeration system  22  may employ any of a variety of suitable refrigeration cycles or techniques that are well known in the art to generate conditioned air. In the illustrated embodiment, the refrigeration system  22  includes a compressor  24 , a condenser  26 , a condenser fan  28 , a motor  30 , an expansion valve  32 , an evaporator  34 , a blower  36 , a motor  38  and a variable frequency drive  40 , interconnected to carry out a refrigeration cycle. The VFD includes a first variable frequency drive  42  configured to receive transmitted power from one or more power conductors and to regulate the motor  30  and a second variable frequency drive  44  configured to receive transmitted power from the one or more power conductors and to regulate the motor  38 . As will be appreciated by those skilled in the art, the drives may include various circuit topologies known in the art, such as inverters, converters, and so forth, capable of producing a desired output frequency that, in turn, produces a desired rotational speed of the motors. 
         [0019]    During operation, a refrigerant flows through the refrigeration system  22 , which produces conditioned air that is expelled to the aircraft. For example, one exemplary refrigerant path is shown by the arrows in  FIG. 1 . In such a path, the vaporized refrigerant enters the compressor  24  where it is compressed at generally constant entropy to form a compressed vaporized refrigerant. The resulting refrigerant enters the condenser  26 , which removes heat and condenses the vaporized refrigerant into a liquid. The liquid refrigerant then enters the expansion valve  32 , which decreases the pressure of the liquid refrigerant. The refrigerant then flows through coils of the evaporator  34 . While flowing through the evaporator  34 , the refrigerant is vaporized, absorbing heat due to the latent heat of vaporization, and cools the ambient air moved over the evaporator coils by the blower  36 . The vaporized refrigerant exits the evaporator  34  and enters the compressor  24  to continue the cycle. 
         [0020]    The illustrated refrigeration system  22  relies on the fan  28  to blow air away from the condenser  26  for heat rejection during operation. Accordingly, the fan  28  is coupled to the multi-voltage induction motor  30 , which drives its operation. The motor  30  is connected to the first variable frequency drive  42 . The first variable frequency drive  42  controls the frequency of the high voltage power supplied to the multi-voltage induction motor  30 . As such, the first VFD  42  allows the motor  30  to be wired in the lower voltage configuration but to receive the higher voltage supply. That is, in the illustrated embodiment, by overspeeding the motor  30 , the size and weight of the motor  30  may be reduced as compared to traditional systems that match the supply voltage with the wiring configuration. 
         [0021]    Similarly, the illustrated refrigeration system  22  also relies on the multi-voltage induction motor  38  to drive the operation of the blower  36 , as indicated by arrow  46 . As before, the motor  38  is coupled to the second frequency drive  44 , which allows the motor  38  to be over-sped during operation. That is, the multi-voltage motor  38  may be wired for a lower voltage but operated with a higher supply voltage to ensure a high power output while reducing the size and weight of the motor as compared to traditional designs in which the wiring configuration matches the supply voltage level. 
         [0022]    It should be noted that although in the illustrated embodiment, the variable frequency drive  40  includes two VFDs, in other embodiments, the VFD  40  may include any suitable number of VFDs that may be coupled to any number of multi-voltage over-sped motors. As such, in further embodiments, the refrigeration system  22  may include more or fewer motors than illustrated in  FIG. 2  that may drive fans, blowers, or any other components of the refrigeration system  22 . For example, an additional multi-voltage induction motor may be coupled to an additional fan or blower configured to direct ambient air over an intercooler of the blower  36 . Indeed, any number of multi-voltage induction motors may be over-sped and utilized in the refrigeration system  22 . 
         [0023]      FIG. 3  is a pressure-flow graph  48  illustrating exemplary effects of overspeeding the multi-voltage induction motors described herein. The graph  48  includes a pressure axis  50  and a flow axis  52 . The graph  48  also includes a duct system flow curve  54 , a lower speed blower curve  56 , and a higher speed blower curve  58 . The graph  48  further includes a rated operating point  60  and an oversped operating point  62 . That is, the lower speed blower curve  56  reflects operation of the blower when a multi-voltage induction motor is wired in a low voltage configuration and operated with a low voltage supply voltage; the induction motor is not oversped. The higher speed blower curve  58  reflects operation of the blower when the multi-voltage induction motor is wired in the low voltage configuration but operated with the higher supply voltage; the induction motor is oversped. As such, the higher speed blower curve  58  demonstrates exemplary effects that may be achieved by overspeeding the multi-voltage induction motor in some embodiments. 
         [0024]    As illustrated, during use, the operating points of the higher speed blower and the lower speed blower are determined by the intersection of the duct system flow curve  54  with the high speed blower curve  58  and the lower speed blower curve  56 . That is, in the illustrated example, the lower speed blower curve  56  and the duct system flow curve  54  intersect at operating point  60 . Furthermore, the higher speed blower curve  58  and the duct system flow curve  54  intersect at operating point  62 . As such, in the illustrated embodiment, advantages may be obtained by operating at the operating point  62  of the higher speed blower rather than operating at the operating point  60  of the lower speed blower. For example, operation at point  60  results in a first flow level  64  and a first pressure level  66 , which are lower than a second flow level  68  and a second pressure level  70  that are obtained by operating at the second operating point  62 . As such, operation along the higher speed blower curve  58  may achieve higher flow levels and higher pressure levels that operation along the lower speed blower curve  56 . That is, by overspeeding the multi-voltage induction motor, higher flows and pressures may be obtained from the blower or fan during operation. 
         [0025]      FIG. 4  is a graph  72  illustrating exemplary schematic plots comparing oversped induction motor characteristics with those of a traditional induction motor. Specifically, the graph  72  includes a torque axis  74 , a motor speed axis  76 , a horsepower axis  78 , an oversped torque plot  80 , a traditional torque plot  82 , an oversped horsepower plot  84 , and a traditional horsepower plot  86 . The oversped torque plot  80  represents exemplary torque characteristics generated with a motor wired in a low voltage configuration but operated with a high voltage power source. The traditional torque plot  82  represents exemplary torque characteristics generated with a motor wired in a high voltage configuration and operated with a high voltage power source. Likewise, the oversped horsepower plot  84  represents exemplary horsepower characteristics generated with a motor wired in a low voltage configuration but operated with a high voltage power source. The traditional horsepower plot represents exemplary horsepower characteristics generated with a motor wired in a high voltage configuration and operated with a high voltage power source. 
         [0026]    As illustrated, the traditional torque plot  82  falls off at a first speed  88 , and the oversped torque plot  80  does not fall off until a second speed  90  higher than the first speed  88 . As such, the oversped motor maintains torque level  92  to the higher speed  90  than the traditional motor, which maintains torque level  92  only until the lower speed  88 . In some embodiments, such a feature of the oversped motor may enable the oversped motor to achieve a higher horsepower output  94  as compared to the traditional motor horsepower output  96 . That is, while the traditional horsepower plot  86  levels off at the lower motor speed  88 , the oversped horsepower plot  84  increases until leveling off at the higher motor speed  90 . Since the oversped motor continues to increase horsepower output until the higher motor speed  90 , the oversped motor may be capable of producing the higher horsepower output  94 . Accordingly, embodiments of the presently disclosed oversped induction motors may offer distinct advantages over traditional systems, which are wired in a high voltage configuration and operated with a high voltage power source. 
         [0027]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.