Abstract:
A fan for use in agriculture which has a BLDC motor which allows for varying the speed of the fan to vary the airflow rate of the fan and vary the efficiency of the fan. A ventilation system for use in a livestock confinement building to maximize a rate of growth of the livestock. A process for maximizing the growth of livestock in a livestock confinement building by controlling the airflow in the livestock confinement building.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/175,970, filed May 6, 2009, which is hereby incorporated herein by reference in its entirety, except that the present application supersedes any portion of the above referenced application which is inconsistent with the present application. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
       [0003]    The present invention relates to a fan for use in agriculture which includes a brushless direct current (BLDC) motor. In particular, the present invention relates to a fan for use in livestock confinement buildings which has a propeller size of between about 36 inches (914 mm) and 84 inches (2134 mm) and which uses a BLDC motor with an electronic control system to optimize the revolutions per minute (rpm), airflow and efficiency of the fan during the various growing stages of the livestock or animals which is needed to maximize the growth rate of the animals and optimize the efficiency of the fan and ventilation system. 
         [0004]    In the past, ventilation systems for livestock confinement buildings used induction motors and controlled ventilation by either turning “on” or “off” some or all of the fans. However, this method often created peaks and valleys in the ventilation of the building where the fans were either “on” or “off”. In addition, in the past airflow rates in the livestock confinement building would vary due to building pressure, wind effects, clogged inlets and other conditions, these conditions affected the ability of the fans to move air. This created periods where the environment and airflow rate in the livestock confinement building was not optimized for the maximum growth of the livestock in the livestock confinement building. In addition, in the past, with fans having induction motors, to make large changes in the airflow of a fan, the motor and/or drive system of the fan was replaced. Thus, there was no easy way to change the speed or airflow of the fans without changing or adding equipment. There was also little ability to operate the fans at peak efficiency while maintaining optimal growth conditions for the livestock in the livestock confinement buildings. There remains a need for a fan for use in livestock confinement buildings which uses a BLDC motor and an electronic control system so that the fan can be operated in a variety of modes and can be easily switched between modes to maximize the efficiency of the fans while optimizing the growing environment of the buildings for the livestock. The substance and advantages of the present invention will become increasingly apparent by reference to the following drawings and the description. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    A fan for use in agriculture which has a BLDC motor. The fan includes a propeller, a center hub, a BLDC motor, a main strut and a control system. The center hub is a bearing unit which has a main shaft rotatably attached to a mounting shaft. The stator of the BLDC motor is fixably mounted on the main strut. The rotor of the BLDC motor as well as the propeller are mounted to the mounting shaft of the center hub. The bearings of the center hub allow the rotor and propeller to rotate while the stator remains stationary. The use of the main strut supports and locates the motor and its parts and allows for mounting of the fan in existing fan housings. 
         [0006]    The control system for the fan controls the speed of the BLDC motor and the fan which controls the airflow rate of the fan. The control system includes at least one (1) microprocessor having programs for controlling the operation of the fan. In one (1) embodiment, the control system has at least two (2) microprocessors. The first microprocessor is preprogrammed to run the standard operations of the motor such as turning the BLDC motor “on” and “off”. The second microprocessor is programmable and includes customized programs to control the speed of the BLDC motor. In one (1) embodiment, the control system has jumpers which determine which customized programs are downloaded from the EEPROMs to the second microprocessor. In one (1) embodiment, the control system also includes manual controls. In one (1) embodiment, the control system includes a variable voltage input. In this embodiment, a voltage between 0 to 10V DC is input into a variable voltage input to vary the speed of the BLDC motor. In another embodiment, the control system has a logic signal input. In this embodiment, a 120V AC logic signal is inputted into the logic signal input to switch the BLDC motor from one (1) speed or operating mode to a different speed or operating mode. The logic signal input acts as a switch. In one (1) embodiment, the control system can be preprogrammed to operate the fan in two (2) modes. The first mode is the high efficiency mode where the speed of the fan varies and thus the airflow rate (CFM) produced by the fan varies to maintain the highest operating efficiency. The second mode is the maximum performance mode where the speed of the fan remains constant. In another embodiment, the fan can operate in four (4) different modes. The first mode is the constant speed mode which operates the BLDC motor at a constant speed. The second mode is the constant airflow rate where the speed of the propeller is varied as necessary to maintain the desired airflow rate under differing pressures. The fan can also operate in a third, constant torque mode or a fourth, constant or maximum efficiency mode. 
         [0007]    A plurality of the fans can be used in a ventilation system for a livestock confinement building. The ventilation system provides ventilation to the livestock confinement building to optimize the environmental conditions in the livestock confinement building to maximize the growth of the livestock. The speed of the fans in the ventilation system can be adjusted to optimize the environmental conditions in the livestock confinement building. The fans can run at different speeds to achieve the correct ventilation and airflow rate in the livestock confinement building. In one (1) embodiment, one or more of the fans in the ventilation system can be “on” or “off” or operating at half speed or operating at any speed from “off” to full speed. The ability to separately control the speeds of the fans in the ventilation system allows for better control of the airflow rate in the livestock confinement building and prevents peaks and valleys in the airflow rate. The ability to individually adjust the speeds of the various fans of the ventilation system enables a user to achieve the desired airflow in the livestock confinement building while maximizing the efficiency of the ventilation system. 
         [0008]    The present invention relates to a fan for use in agriculture which comprises a main strut, a center hub having a mounting shaft rotatably connected to a main shaft with the main shaft fixably mounted on the main strut, a BLDC motor having a rotor and a stator with the stator fixably mounted on main strut and the rotor fixably mounted on the mounting shaft of the center hub, a propeller fixably mounted on the mounting shaft of the center hub adjacent the rotor on a side opposite the stator, and a control system connected to the BLDC motor for controlling the operation of the BLDC motor. 
         [0009]    Further, the present invention relates to a method for providing a constant airflow rate in a livestock confinement building which comprises the steps of providing a plurality of BLDC fans in the livestock confinement building, and controlling a speed of each of the fans to control an airflow rate of each fan to maintain a constant airflow rate in the livestock confinement building. 
         [0010]    Still further, the present invention relates to a process for maximizing growth of livestock in a livestock confinement building, which includes the steps of providing a plurality of BLDC fans in the livestock confinement building, monitoring environmental conditions in the livestock confinement building, and controlling an air flow rate in the livestock confinement building to maintain predetermined environment conditions by controlling a speed of each of the fans to maintain a desired air flow rate in the livestock confinement building which maximizes the growth of the livestock. 
         [0011]    Further still, the present invention relates to a ventilation system for a livestock confinement building, which comprises a plurality of fans having a BLDC motor and having a propeller with a size of between approximately 36 inches (914 mm) to 84 inches (2134 mm), and a control system for controlling a speed of the fans. 
         [0012]    The substance and advantages of the present invention will become increasingly apparent by reference to the following drawings and the description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an exploded view of the fan  10  of the present invention showing the propeller  36 , the rotor cover  24 , the rotor  22 , the center hub  38 , the stator  14 , the control system  40 , the heat sink cover  34 , and the main strut  20  for mounting the motor  12  to the fan housing  100 . 
           [0014]      FIG. 2  is a side exploded view of the fan  10  of the present invention. 
           [0015]      FIG. 2A  is an end view of the fan  10  showing the heat sink cover  34 . 
           [0016]      FIG. 3  is a top view of the stator mount  16  for the single lamination stack assemblies  18  of the BLDC motor  12  of the fan  10 . 
           [0017]      FIG. 4  is a cross-sectional view along the line  4 - 4  of  FIG. 3 . 
           [0018]      FIG. 5  is an isometric view of the wound, single lamination stack assembly  18 . 
           [0019]      FIG. 6  is a perspective view of the main housing  42  for the BLDC motor  12 . 
           [0020]      FIG. 7  is an isometric view of the rotor hub  26  for the BLDC motor  12 . 
           [0021]      FIG. 8  is an isometric view of the magnet  30 . 
           [0022]      FIG. 9  is a top view of the rotor hub  22  showing the rotor hub  26 , the flux ring  28  and magnets  30 . 
           [0023]      FIG. 10  is a top view of one (1) section of the lamination retainer  32  for the stator  14 . 
           [0024]      FIG. 11  is a right side view along the line  11 - 11  of  FIG. 10 . 
           [0025]      FIG. 12  is a top view of the stator  14  showing the stator mount  16 , the single lamination stack assemblies  18  mounted around the circumference of the stator mount  16 , and the lamination retainer  32  for securing the single lamination stack assemblies  18  to the stator mount  16 . 
           [0026]      FIG. 13  is a side view of the stator  14  and stator mount  16 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    A fan  10  for use in ventilation in agriculture such as for ventilation of livestock confinement buildings. Livestock can include chickens, cows, pigs, etc. The ventilation system for a livestock confinement building can include a plurality of fans  10 . The fans  10  can operate independently or together as part of the ventilation system for the livestock confinement building. The ventilation system controls the environment of the livestock confinement building to optimize the growth of the livestock in the livestock containment building. 
         [0028]    The fan  10  includes a propeller  36  and a BLDC motor  12  ( FIGS. 1 and 2 ). In one (1) embodiment, the fan  10  includes a main strut  20  which supports and locates the motor  12  and the various components of the fan  10  and allows the fan  10  to be mounted in a fan housing  100 . In one (1) embodiment, the main strut  20  enables the fan  10  to be easily mounted in existing fan housing to replace an existing fan. The fan  10  is a direct drive, axial fan with the propeller  36  mounted directly to the motor  12 . The use of direct drive eliminates the need to repair and replace belts which limits the downtime of the fan  10  and reduces the operating cost. In one (1) embodiment, the propeller  36  has three (3) blades. However, it is understood that any fan propeller well known in the art can be used. It is intended that the fan  10  can be retrofit into existing fan housings used for existing fans. In one (1) embodiment, the fan  10  is an axial exhaust, inlet or recirculation fan having a diameter of between approximately 36 inches (914 mm) and 84 inches (2134 mm). In one (1) embodiment, the similar sized BLDC motors  12  are used for all fans  10  having a size of between approximately 36 inches (914 mm) and 84 inches (2134 mm). 
         [0029]    The fan  10  has a center hub  38 . The center hub  38  has a main shaft  38 A and a mounting shaft  38 B rotatably connected to the main shaft  38 A ( FIG. 2 ). The main shaft  38 A of the center hub  38  is fixably mounted through the main strut  20  of the fan  10 . The center hub  38  has bearings to allow the mounting shaft  38 B to rotate while the main shaft  38 A remains stationary. In one (1) embodiment, the center hub  38  is similar to center hubs well known for use in ventilation fans for agricultural use. In one (1) embodiment, the propeller  36  is mounted on the mounting shaft  38 A of the center hub  38 . 
         [0030]    The BLDC motor  12  includes a stator  14  and a rotor  22 . In one (1) embodiment, the BLDC motor  12  is a 3-phase motor having 16 magnetic poles and  24  electrical poles. In one (1) embodiment, the BLDC motor  12  is an outer-rotor motor having the rotor  22  mounted outside of and around the stator  14 . The rotor  22  includes a rotor hub  26 , a flux ring  28  and magnets  30 . The rotor  22  is covered by a rotor cover  24 . In one (1) embodiment, the rotor cover  24  is mounted to the rotor hub  26 . In one (1) embodiment, the rotor hub  26  has an outer ring connected to a center portion. The magnets  30  are mounted on the inner surface of the outer ring of the rotor hub  26  and are spaced apart around the circumference of the inner surface of the outer ring. In one (1) embodiment, the magnets  30  are constructed of ceramic or neodymium magnetic material. The rotor hub  26  is mounted to the mounting shaft  38 B of the center hub  38 . In one (1) embodiment, the propeller  36  is mounted on the rotor hub  26 . 
         [0031]    The stator  14  includes a stator mount  16 , single lamination stack assemblies  18  mounted on the stator mount  16  and a lamination retainer  32  for securing the single lamination stack assemblies  18  on the stator mount  16  ( FIGS. 12 and 13 ). In one (1) embodiment, the stator  14  has a low profile with pancake shaped lamination stack assemblies  18  having a height of between approximately 1.00 to 2.50 inches (25.4 mm to 63.5 mm). In one (1) embodiment, the lamination stack assemblies  18  have a height of approximately 1.25 inches (31.75 mm). In one (1) embodiment, the stator  14  has an outer diameter of between approximately 10 inches to 14 inches (254 mm to 356 mm). In one (1) embodiment, the rotor hub  26  has an inner diameter of between approximately 11 inches and 15 inches (279 mm to 381 mm). In one (1) embodiment for a 13 inch (330 mm) BLDC motor  12 , the flux ring  28  of the rotor  22  has an inner diameter of 12.5 inches (318 mm) and an outer diameter of 12.8 inches (326 mm). The stator  14  is fixably mounted on the main strut  20 . A main housing  42  is optionally provided to cover the stator  14  ( FIG. 6 ). In one (1) embodiment, the main housing  42  is mounted on the main strut  20 . In one (1) embodiment, the rotor  22  is covered by the main housing  42  except that the rotor hub  26  of the rotor  22  extends slightly beyond the main housing  42  in a direction opposite the main strut  20 . The main housing  42  and the rotor cover  24  essentially completely enclose the rotor  22  and the stator  14  of the motor  12 . 
         [0032]    A heat sink cover  34  is mounted to the main strut  20  of the fan  10  on the inlet side of the fan  10  opposite the propeller  36 , rotor  22  and stator  14  ( FIG. 2A ). In one (1) embodiment, the heat sink cover  34  acts as a cover for the motor  12  and prevents debris from entering the motor  12 . The aerodynamic shape of the heat sink cover  34  reduces the interference in air flowing over the motor  12 . In one (1) embodiment, an aerodynamic cover  44  is provided over the main strut  20  to reduce the disruption of air flow caused by the main strut  20 . 
         [0033]    The BLDC motor  12  is controlled by an electronic control system  40 . In one (1) embodiment, the control system  40  is structurally similar to those well known in the art for controlling BLDC motors and includes one or more microprocessors, a rectification circuit that converts incoming AC line voltage to DC and conditions the incoming power, a final IGBT (Internal Gate Bi-Polar Transistor) module that is essentially a high-power, high speed, low resistance solid state switching device which turns the coils of the motor  12  “on” and “off”. In one (1) embodiment, the control system  40  has two (2) mircoprocessors. The first microprocessor includes the standard operating programming for controlling standard operations of the motor  12 . The second microprocessor allows for using customized programs for customizing the operation of the motor  12 . In one (1) embodiment, the control system  40  has an EEPROM which has a plurality of different programs which change the operation of the fan  10 . In one (1) embodiment, the control system  40  is provided with jumpers. In one (1) embodiment, the jumpers are wires. The connection or removal of jumpers in the control system  40  determines which program from the EEPROM will be downloaded into the second microprocessor which determines how the fan  10  will operate. Each jumper corresponds to a different program in the EEPROM. The jumpers enable a user to select the fixed speed of the fan  10 . The jumpers enable a user to change the peak horsepower and RPM of the fan  10  while using the same motor  12 . In one (1) embodiment, the control system  40  for operating the fan  10  is mounted on the fan housing  100  of the fan  10 . In another embodiment, the control system  40  is mounted adjacent the main strut  20  in the heat sink cover  34  adjacent the inlet of the fan  10 . The shape of the heat sink cover  34  and the cooling fins on the outer surface of the heat sink cover  34  help to keep the electronic control system  40  cool. 
         [0034]    By electronically controlling the airflow produced by the fan  10  or ventilation system having a plurality of fans (such as by controlling the airflow of each individual fan or by shutting off unnecessary fans), each fan  10  can be used most efficiently based on the growing stages of the livestock in the livestock confinement building. The control system  40  can be specifically designed for each livestock confinement building by mapping the required airflow to any livestock confinement building. The control system  40  can be adjusted based on the various stages of growth of the livestock in a livestock confinement building. Some of the variables that can be considered when programming the control system  40  so that the fan  10  operates efficiently are building temperature, air velocity in the building, livestock water consumption, livestock weight and feed supply rate. In one (1) embodiment, another variable which is considered when programming the fan  10  is ventilation rate. Ventilation rate is airflow per animal. For example, in a poultry house, ventilation rate would be CFM/bird. Another variable which may be considered is humidity in the building. 
         [0035]    In one (1) embodiment, the speed of the fan  10  can be adjusted without reconfiguring the control system  40  or reprogramming the microprocessor of the control system  40 . In one (1) embodiment, the control system has a variable voltage input and a user can input an analog signal between 0-10V DC to the variable voltage input. The speed of the fan  10  can be continually adjusted based on the amplitude of the analog signal. In one (1) embodiment, an input of 10V DC corresponds to a speed of approximately half maximum speed and an input of 0V DC corresponds to a speed of approximately maximum speed. In one (1) embodiment, the control system  40  is preprogrammed to operate the fan  10  in two (2) modes. The fan  10  can be run in a high efficiency mode or a maximum performance mode. In the high efficiency mode, the speed of the fan  10  varies and thus the airflow rate (CFM) produced by the fan  10  varies. However, the energy consumed (power input, watt) by the fan  10  remains relatively constant. In the maximum performance mode, the airflow rate remains essentially constant. However, energy consumption of the fan  10  varies and thus the fan  10  tends to be less efficient in maximum performance mode. In one (1) embodiment, the switching between modes is automatic based on variables preselected by the user. In another embodiment, the user manually selects in which mode the fan  10  operates such as by flipping a switch. In one (1) embodiment, the control system  40  includes logical signal input and the mode of the fan  10  can be changed by inputting a signal to the logic signal input. In one (1) embodiment, the signal is a 120V AC “logic” signal. In one (1) embodiment, the input of the 120V AC “logic” signal switches the fan  10  from maximum performance mode to high efficiency mode. In one (1) embodiment, the 120V AC “logic” signal is used to switch the fan  10  from full airflow rate to half airflow rate. 
         [0036]    In one (1) embodiment, the fan  10  is able to operate in four (4) different modes. In the first, constant speed mode, the propeller  36  rotates at a constant speed (RPM). The control system  40  keeps the speed of the propeller  36  constant by adjusting the power to the motor  12  based on monitored conditions. The control system  40  receives feedback from the motor  12  and adjusts the motor  12  to achieve the constant speed. In a second, constant airflow mode, the control system  40  adjusts the speed of the propeller  36  to achieve a constant airflow rate. The control system  40  receives feedback from the motor  12  and adjusts the speed of the propeller  36  to achieve the predetermined airflow rate. Thus, as the static pressure in the building changes, the speed of the fan  10  is automatically adjusted so that the airflow rate remains constant. The control system  40  can also be used to maintain the fan  10  in a third, constant torque mode or a fourth, constant or maximum efficiency mode. The control system  40  is a sensorless control system which receives feedback from the motor  12  and which does not use any feedback sensors. The control system  40  is a closed loop operation. In this embodiment, the motor  12  uses back-EMF to detect the position of the rotor  22  of the motor  12 . Back-EMF and zero crossing detection are used to determine the direction of the rotation of the motor  12  and to detect the speed of the motor  12 . 
         [0037]    In one (1) embodiment, where the fan  10  is part of a ventilation system having a plurality of fans  10 , each control system  40  for each fan  10  is programmed based on the results for the overall ventilation system. For example, for some early stages of livestock growth in a livestock confinement building, the airflow rate which is needed is less than the maximum airflow rate which can be provided by the ventilation system. In this instance, the control systems  40  for some of the fans  10  will shut the fans  10  down while the control systems  40  for other fans in the ventilation system will continue to run the fans  10  at full speed. In another embodiment, to reduce the airflow rate of the ventilation system, the control systems  40  for all of the fans  10  arc programmed to run some or all of the fans  10  at a reduced speed. In one (1) embodiment, operating multiple fans  10  at a reduced speed to obtain the desired airflow rate is more efficient than operating fewer fans  10  at full speed to obtain the same air flow rate. In one (1) embodiment, the ventilation system is operated by a central control system which controls each of the control systems  40  for each of the individual fans  10  of the ventilation system. In another embodiment, the control system  40  for each fan  10  of the ventilation system is preprogrammed to provide a set airflow rate at set times based on the stages of growth of the livestock in the livestock confinement building. In one (1) embodiment, the fans  10  are controlled such that the environment conditions in the livestock confinement building allows for the maximum growth rate for less feed. Thus, the ventilation system is used to optimize the feed conversion rate for the livestock in the livestock confinement building. In one (1) embodiment, the feed conversion rate is maximized by leveling out the ventilation or airflow rate provided by the fans  10  so that the environmental conditions in the livestock confinement building remain at a steady state without dramatic changes. The environmental conditions are adjusted as necessary to provide optimum feed conversion rate throughout the growing cycle of the livestock. In one (1) embodiment, the control system  40  for the fans  10  enable the fans  10  to provide a constant airflow rate in the livestock confinement building. The fans  10  of the ventilation system operate at a range of speeds appropriate for livestock ventilation systems. In one (1) embodiment, the fan  10  operates at a speed of less than 650 RPM. In one (1) embodiment, the motor  12  provides a torque of greater than 10 ft-lbs. The motor  12  is able to operate over a wide range of supply voltages. Thus, the difficulties associated with operating fans in facilities having older wiring or faulty wiring systems are reduced. The fan  10  with the BLDC motor  12  is able to operate in a variety of environmental conditions including extreme high and low temperatures. In one (1) embodiment, the fan  10  is able to operate in ambient temperatures from approximately −30° C. to 55° C. (−22° F. to 131° F.). 
         [0038]    In one (1) embodiment, the fan  10  uses a soft-start to reduce inrush effects on the electrical supply line due to the starting of all the fans  10  in a building simultaneously. The fan  10  eases into operation by slowly providing a very low supply voltage to the motor  12  and then gradually increasing the voltage until the desired operating speed for the fan  10  is obtained. The use of a soft-start enables all the fans of a ventilation system for a building to be turned on simultaneously without overburdening the electrical supply line which allows a smaller, less expensive back-up generator to be used. 
         [0039]    In one (1) embodiment, the control system  40  is programmed to automatically rotate the propeller  36  briefly in the backward direction when the fan  10  is shut down. When the propeller  36  is rotated in the backward direction, the movement of the propeller  36  moves air out of the inlet of the fan  10  which closes the damper on the outlet of the fan  10  to prevent conditioned air in the building from exiting the building. 
         [0040]    Testing of the fan  10  of the present invention having the BLDC motor  12  compared to similarly sized fans using AC motors shows that the fan  10  of the present invention is more efficient than fans currently in use. Table 1 shows the fan efficiency of the fan  10  having a BLDC motor (Fan 1) as compared to a fan having a standard 1 horsepower single phase AC motor (Fan 2) where the fan speed is kept constant at a nominal speed of 460 rpm over a range of static pressures. For a static pressure of 0.0 inches, Fan 1 had an increased efficiency over Fan 2 of 18.3%. For a static pressure of 0.05 inches, Fan 1 had an increased efficiency over Fan 2 of 18.5%. For a static pressure of 0.10 inches, Fan 1 had an increased efficiency over Fan 2 of 15.2%. For a static pressure of 0.15 inches, Fan 1 had an increased efficiency over Fan 2 of 14.5%. For a static pressure of 0.20 inches, Fan 1 had an increased efficiency of 8.9% over Fan 2. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 FAN 1 
                 FAN 2 
               
               
                   
               
             
             
               
                 Motor Type 
                 BLDC 
                 Standard, 1 Hp, single phase AC 
               
               
                 Fan Speed 
                 460 
                 460 
               
               
                 RPM nominal 
                   
                   
               
               
                 Airflow Ratio 
                 0.71 
                 0.75 
               
               
                   
               
             
          
           
               
                   
                   
                 Airflow 
                 Power 
                 Fan 
                 Airflow 
                 Power 
                 Fan 
               
               
                   
                   
                 Rate 
                 Input 
                 Efficiency 
                 Rate 
                 Input 
                 Efficiency 
               
               
                   
                   
                 CFM 
                 Watt 
                 CFM/Watt 
                 CFM 
                 Watt 
                 CFM/Watt 
               
               
                   
               
               
                 Static 
                 0.0 
                 27,400 
                 919 
                 29.8 
                 27,000 
                 1,072 
                 25.2 
               
               
                 Pressure 
                 0.05 
                 25,700 
                 957 
                 26.9 
                 25,200 
                 1,110 
                 22.7 
               
               
                 Inches 
                 0.10 
                 23,400 
                 994 
                 23.5 
                 23,200 
                 1,140 
                 20.4 
               
               
                   
                 0.15 
                 21,000 
                 1,028 
                 20.5 
                 21,000 
                 1,179 
                 17.9 
               
               
                   
                 0.20 
                 18,200 
                 1,060 
                 17.1 
                 18,800 
                 1,196 
                 15.7 
               
               
                   
               
             
          
         
       
     
         [0041]    Table 2 shows the fan efficiency over a range of static pressures for the fan  10  of the present invention having the BLDC motor (Fan 1) and for a fan having a standard 1.5 horsepower, single phase, AC motor (Fan 2) where the fan speed is kept constant at a nominal speed of 510 rpm. For a static pressure of 0.0 inches, Fan 1 had an increased efficiency over Fan 2 of 19.1%. For a static pressure of 0.05 inches, Fan 1 had an increased efficiency over Fan 2 of 18.2%. For a static pressure of 0.10 inches, Fan 1 had an increased efficiency over Fan 2 of 15.8%. For a static pressure of 0.15 inches, Fan 1 had an increased efficiency over Fan 2 of 16.6%. For a static pressure of 0.20 inches, Fan 1 had an increased efficiency of 17.2% over Fan 2. Table 2 also shows that Fan 1 had an airflow ratio of 0.79 while Fan 2 had an airflow ratio of 0.78. Airflow ratio is the ability of the fan to maintain airflow rate as static pressure increases. The higher the airflow ratio the better the ability of the fan to maintain the airflow rate as the static pressure increases. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 FAN 1 
                 FAN 2 
               
               
                   
               
             
             
               
                 Motor Type 
                 BLDC 
                 Standard, 1.5 Hp, single phase AC 
               
               
                 Fan Speed 
                 510 
                 510 
               
               
                 RPM nominal 
                   
                   
               
               
                 Airflow Ratio 
                 0.79 
                 0.78 
               
               
                   
               
             
          
           
               
                   
                   
                 Airflow 
                 Power 
                 Fan 
                 Airflow 
                 Power 
                 Fan 
               
               
                   
                   
                 Rate 
                 Input 
                 Efficiency 
                 Rate 
                 Input 
                 Efficiency 
               
               
                   
                   
                 CFM 
                 Watt 
                 CFM/Watt 
                 CFM 
                 Watt 
                 CFM/Watt 
               
               
                   
               
               
                 Static 
                 0.0 
                 29,700 
                 1,226 
                 24.3 
                 30,100 
                 1,474 
                 20.4 
               
               
                 Pressure 
                 0.05 
                 28,300 
                 1,281 
                 22.1 
                 28,500 
                 1,526 
                 18.7 
               
               
                 Inches 
                 0.10 
                 26,400 
                 1,333 
                 19.8 
                 26,900 
                 1,579 
                 17.1 
               
               
                   
                 0.15 
                 23,400 
                 1,381 
                 17.6 
                 24,600 
                 1,627 
                 15.1 
               
               
                   
                 0.20 
                 22,300 
                 1,420 
                 15.7 
                 22,300 
                 1,663 
                 13.4 
               
               
                   
               
             
          
         
       
     
         [0042]    Table 3 shows the fan efficiency over a range of static pressures for the fan  10  of the present invention having the BLDC motor (Fan 1) and a standard 1.5 horsepower, single phase, AC motor (Fan 2) where the power input is essentially the same for both fans. For a static pressure of 0.0 inches, Fan 1 had an increased efficiency over Fan 2 of 9.7%. For a static pressure of 0.05 inches, Fan 1 had an increased efficiency over Fan 2 of 11.3%. For a static pressure of 0.10 inches, Fan 1 had an increased efficiency over Fan 2 of 12.6%. For a static pressure of 0.15 inches, Fan 1 had an increased efficiency over Fan 2 of 16.6%. For a static pressure of 0.20 inches, Fan 1 had an increased efficiency of 23.0% over Fan 2. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                 FAN 1 
                 FAN 2 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Motor Type 
                 BLDC 
                 Standard, 1 Hp,  
               
               
                   
                   
                 single phase AC 
               
               
                 Fan Speed  
                 Varies 
                 365 
               
               
                 RPM nominal 
                   
                   
               
               
                 Airflow Ratio 
                 0.78 
                 0.70 
               
               
                   
               
             
          
           
               
                   
                   
                 Airflow 
                 Power 
                 Fan 
                 Airflow 
                 Power 
                 Fan 
               
               
                   
                   
                 Rate 
                 Input 
                 Efficiency 
                 Rate 
                 Input 
                 Efficiency 
               
               
                   
                   
                 CFM 
                 Watt 
                 CFM/Watt 
                 CFM 
                 Watt 
                 CFM/Watt 
               
               
                   
               
               
                 Static 
                 0.0 
                 22,600 
                 997 
                 22.7 
                 20,600 
                 995 
                 20.7 
               
               
                 Pressure 
                 0.05 
                 21,300 
                 1,031 
                 20.7 
                 19,200 
                 1,031 
                 18.6 
               
               
                 inches 
                 0.10 
                 19,900 
                 1,054 
                 18.8 
                 17,700 
                 1,059 
                 16.7 
               
               
                   
                 0.15 
                 18,300 
                 1,084 
                 16.9 
                 15,700 
                 1,082 
                 14.5 
               
               
                   
                 0.20 
                 16,600 
                 1,106 
                 15.0 
                 13,400 
                 1,100 
                 12.2 
               
               
                   
               
             
          
         
       
     
         [0043]    Table 4 shows the fan efficiency of the fan  10  of the present invention having a BLDC motor over a range of static pressures where the airflow rate is constant at 22,500 CFM and 25,000 CFM. The fan  10  at both airflow rates has an airflow ratio of 1.0. The fan  10  is capable of attaining an airflow ratio of 1.0 or greater. No other large agricultural ventilation fan has this capability. This means that the fan  10  can be operated in such a manner as to overcome variations in static pressure, within the capabilities of the fan  10 , caused by dust build-up, restricted building air inlets, cooling pads, light filters, or windy site conditions and maintain a constant airflow rate. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
             
             
               
                 Airflow Rate CFM 
                 22,500 
                 25,000 
               
               
                 Motor Type 
                 BLDC 
                 BLDC 
               
               
                 Fan Speed RPM nominal 
                 Varies 
                 varies 
               
               
                 Airflow Ratio 
                 1.00 
                 1.00 
               
               
                   
               
             
          
           
               
                   
                   
                 Power 
                 Fan 
                 Power 
                 Fan  
               
               
                   
                   
                 Input 
                 Efficiency 
                 Input 
                 Efficiency 
               
               
                   
                   
                 Watt 
                 CFM/Watt 
                 Watt 
                 CFM/Watt 
               
               
                   
               
               
                 Static 
                 0.0 
                 505 
                 44.6 
                 693 
                 36.1 
               
               
                 Pressure 
                 0.05 
                 685 
                 32.9 
                 879 
                 28.4 
               
               
                 inches 
                 0.10 
                 891 
                 25.3 
                 1,113 
                 22.4 
               
               
                   
                 0.15 
                 1,137 
                 19.8 
                 1,425 
                 17.5 
               
               
                   
                 0.20 
                 1,395 
                 16.2 
                 1,777 
                 14.1 
               
               
                   
               
             
          
         
       
     
         [0044]    Table 5 shows the fan speed, current input, and power input for the fan  10  producing an airflow rate of approximately 22,500 CFM over a range of static pressures. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                 Static Pressure 
                 Airflow Rate 
                 Fan Speed 
                 Current Input 
                 Power Input 
               
               
                 Inches 
                 CFM 
                 RPM 
                 AMPS 
                 Watt 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0.00 
                 22,538 
                 380 
                 3.71 
                 505 
               
               
                 0.05 
                 22,538 
                 415 
                 4.95 
                 685 
               
               
                 0.10 
                 22,506 
                 449 
                 6.29 
                 891 
               
               
                 0.15 
                 22,474 
                 482 
                 7.84 
                 1137 
               
               
                 0.20 
                 22,538 
                 512 
                 9.45 
                 1395 
               
               
                 0.25 
                 22,538 
                 541 
                 11.28 
                 1704 
               
               
                 0.30 
                 22,474 
                 563 
                 13.50 
                 2150 
               
               
                   
               
             
          
         
       
     
         [0045]    Table 6 shows the fan speed, current input and power input for the fan  10  producing an airflow rate of approximately 25,000 CFM over a range of static pressures. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 Static Pressure 
                 Airflow Rate 
                 Fan Speed 
                 Current Input 
                 Power Input 
               
               
                 Inches 
                 CFM 
                 RPM 
                 AMPS 
                 Watt 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0.00 
                 24,999 
                 425 
                 4.95 
                 693 
               
               
                 0.05 
                 24,999 
                 455 
                 6.13 
                 879 
               
               
                 0.10 
                 24,970 
                 487 
                 7.65 
                 1113 
               
               
                 0.15 
                 24,970 
                 522 
                 9.52 
                 1425 
               
               
                 0.20 
                 24,970 
                 554 
                 11.61 
                 1777 
               
               
                   
               
             
          
         
       
     
         [0046]    In the foregoing description, various features of the present invention are grouped together in one or more embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated by reference herein in their entirety, with each claim standing on its own as a separate embodiment of the present invention. 
         [0047]    It is intended that the foregoing description be only illustrative of the present invention and that the present invention be limited only by the hereinafter appended claims.