Abstract:
An electric motor controllable to operate at a number of distinct output speeds. The electric motor includes a single set of mechanical parts in combination with a multiple sets of electromagnetic parts having different configurations, where the number of electromagnetic parts corresponds to the number of distinct output speeds of the electric motor.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to electric motors, and more particularly to electric motors controllable to operate at a number of distinct output speeds. 
     Various electric motor controls have been used to control various electric motors to operate at multiple output speeds. Nevertheless, it would be desirable to have a new electric motor that is controllable by a less expensive controller to provide efficient operation at a number of distinct speeds. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention provides an electric motor that is controllable by an inexpensive controller to independently provide efficient operation at a number of distinct output speeds. The electric motor includes a single set of mechanical parts (e.g., housing, shaft, bearings, etc.) in combination with multiple sets of electromagnetic parts (e.g., first and second stators adapted to independently receive power from the controller and thereby produce first and second magnetic fields, respectively, and first and second rotating members connected to the shaft for rotation therewith and adapted to interact with the first and second magnetic fields), where the number of electromagnetic parts corresponds to the number of distinct output speeds of the electric motor. In some embodiments, each set of electromagnetic parts has a different configuration (e.g., a low speed set, a high speed set, etc.). 
     In one embodiment, the electric motor independently provides either a first or a second output speed. The motor includes two sets of electromagnetic parts (i.e., a first stator and a first rotating member, and a second stator and a second rotating member). The controller independently provides the electric motor either a first or a second power, where the first power corresponds to the first speed and the second power corresponds to the second speed. When the first power is provided, the first stator receives the first power and produces a first magnetic field. The first rotating member interacts with the first magnetic field and, as a result of the interaction, the rotor rotates at the first output speed. Similarly, when the second power is provided, the second stator receives the second power and produces a second magnetic field. The second rotating member interacts with the second magnetic field and, as a result of the interaction, the rotor rotates at the second output speed. 
     The electric motor of the invention can be used in many different environments requiring low numbers (e.g., 2, 3) of distinct output speeds. For example, the electric motor can be incorporated in a heating, ventilation, and air conditioning (HVAC) system to drive a blower assembly at either the first speed or the second speed. The first and second speeds provide a first or a second volume of air, respectively, to the environment the HVAC system is conditioning. 
     In other embodiment, the electric motor provides a different number of output speeds and/or is incorporated in other systems. 
    
    
     Other features of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a HVAC system incorporating an electric motor of the present invention. 
     FIG. 2 is a sectional view of the electric motor shown in FIG.  1 . 
     FIG. 3 is a schematic diagram of the electric motor shown in FIG. 1 and a controller connected to the motor. 
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” and “coupled” are used broadly and encompass both direct and indirect mountings, connections, and. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
     FIG. 1 schematically illustrates an HVAC system  5  having an electric motor  10  of the invention. The electric motor  10  is electrically coupled to a controller  15  and drivingly coupled to a driven unit  20 . As described herein, the HVAC system  5  is a dual capacity heating and cooling system, the functionality of the controller  10  is incorporated in the controls of the HVAC system  5 , and the driven unit  20  is a blower assembly which delivers either a first or a second volume of air to the environment conditioned by the HVAC system  5 . The controller  15  independently provides either a first power V 1  (e.g., an alternating current (AC) power, a direct current (DC) power, etc.) or a second power V 2  (e.g., an AC power, a DC power, etc.) to the motor  10  based on a user input (e.g., an adjustment of a thermostat associated with the HVAC system  5 ) and/or a feedback (e.g., a trigger resulting from a failure to reach a commanded temperature in the environment conditioned by the HVAC system in a set amount of time). As described further below, supplying the first power V 1  to the motor  10  results in a first output motor speed S 1 , and supplying the second power V 2  to the motor  10  results in a second output motor speed S 2 . When the blower assembly  20  is driven at the first output speed S 1 , the first volume of air is provided to the environment, and when the blower assembly  20  is driven at the second output speed S 2 , the second volume of air is provided to the environment. The motor  10  is capable of use in other systems and the HVAC system  5  is shown and described as an example of one such system. 
     As used herein, the first and second output speeds S 1  and S 2 , respectively, may include a range of output speeds. Description of the output speeds S 1  and S 2  as distinct output speeds refers to the generally unvaried supply of the first and second powers V 1  and V 2  which are utilized to generate the first and second output speeds S 1  and S 2 . Although the output speeds S 1  and S 2  may vary based on characteristics of the motor  10  and/or loads applied to the motor  10 , the speeds S 1  and S 2  generally will not vary based on the control provided by the controller  15 . In one embodiment, the first output speed S 1  is a low speed (e.g., 550 revolutions per minute (RPM)) and the second output speed S 2  is a high speed (e.g., 1075 RPM). 
     As shown in FIG. 2, the motor  10  includes a housing  25 , a first stator  30  fixed relative to the housing  25 , a second stator  35  fixed relative to the housing  25 , and a rotor  40 . The rotor  40  includes a shaft  45  rotatable relative to the housing  25  about an axis  50 , a first rotating member  55  connected to the shaft  40  for rotation therewith relative to the first stator  30 , and a second rotating member  60  connected to the shaft  45  for rotation therewith relative to the second stator  35 . 
     The first and second stators  30  and  35 , respectively, are independently electrically coupled to the controller  15  to receive power. In one embodiment, as shown in FIG. 3, the first stator  30  receives the first power V 1  and the second stator  35  receives the second power V 2 . When the first stator  30  receives the first power V 1 , the first stator  30  produces a first magnetic field, and when the second stator  35  receives the second power V 2 , the second stator  35  produces a second magnetic field. The first rotating member  55  interacts with the first magnetic field to produce a first torque in the rotor  40  causing the rotor  40  to rotate at the first output speed S 1 . The second rotating member  60  interacts with the second magnetic field to produce a second torque in the rotor  40  causing the rotor  40  to rotate at the second output speed S 2 . 
     As shown in FIG. 3, in one embodiment, the motor  10  includes a permanent split capacitor induction motor. Each stator  30  and  35  includes a main winding W 1  and a starting or an auxiliary winding W 2 . Each auxiliary winding W 2  is connected in series with a capacitor C for startup and normal operation of the motor  10 . The first and second rotating members  55  and  60 , respectively, include a laminated core, conductor bars running parallel to the axis  50 , and conducting rings located on the longitudinal ends of each rotating member  55  and  60  and electrically coupled to the conductor bars. 
     As the first power V 1  (e.g., a first AC power) is passed through the windings W 1  and W 2  of the first stator  30 , a moving magnetic field (i.e., the first magnetic field) is formed near the energized stator  30 . The moving magnetic field induces a current in the first rotating member  55 , thereby forming a magnetic field near the first rotating member  55 . Interaction between the field of the first stator  30  and the field of the first rotating member  55  produces a torque on the rotor  40  which causes the rotor  40  to rotate at the first output speed S 1 . Similarly, supply of the second power V 2  to the windings W 1  and W 2  of the second stator  35  results in the rotor  40  rotating at the second output speed S 2 . In one specific embodiment, the first and second powers V 1  and V 2 , respectively, are electrically the same. 
     In other embodiments, the motor  10  includes other types of motors (e.g., AC motors, DC motors, brush motors, brushless motors, etc.) and other types of induction motors (e.g., split-phase, capacitor start/induction run, capacitor start/capacitor run, shaded-pole, etc.). 
     In the illustrated embodiment, the first and second stators  30  and  35 , respectively, each include a standard speed connection HIGH and two alternative speed connections MED and LOW. In other embodiments, the first and second stators  30  and  35  may each independently include different numbers of alternate speed connections (e.g., the first stator  30  includes a standard speed connection and no alternate speed connections, and the second stator  35  includes a standard speed connection and three alternate speed connections). Alternative speed connections are commonly known as taps. The alternative speed connections allow the individual installing the HVAC system  5  to adjust the first and second speeds S 1  and S 2  to fit the particular installation. Variation in equipment and ductwork design changes the first and second volumes of air needed to optimally condition the environment of the HVAC system. Utilization of the alternative speed connections provides flexibility in the installation process. In other embodiments, the first and second stators  30  and  35  may include multiple sets of main windings W 1  and/or auxiliary windings W 2  for adjusting the output speeds S 1  and S 2 . 
     In the illustrated embodiment, the first stator  30  includes ten poles and the second stator  35  includes six poles. In other embodiments, the stator configurations can vary. Further, the first stator  30  and the first rotating member  55  form a low speed, high efficiency set of electromagnetic parts and the second stator  35  and the second rotating member  60  form a high speed, high efficiency set of electromagnetic parts. Utilization of such sets allows for efficient operation at each of the distinct output speeds. 
     In one embodiment, the controller  15  is implemented using a programmable device (e.g., a microprocessor, a microcontroller, a digital signal processor (DSP), etc.) that utilizes software stored in a memory and a discrete power component (e.g., a switch such as a relay, etc.). In other embodiments, the controller  15  may be implemented using other combinations of software and hardware or using solely software or hardware. 
     Based on a user input and/or a feedback, the controller  15  provides either the first power V 1  or the second power V 2  to the motor  10 . In one embodiment, the first and second powers V 1  and V 2  are both 115 volt/60 Hz power. In other embodiments, the first and second powers V 1  and V 2  include other powers (e.g., 230 volts/60 Hz AC power, etc.). 
     Various features of the invention are set forth in the following claims.