Abstract:
Methods and control systems for improving performance in an air filtration system are disclosed. The method includes monitoring performance of a blower motor in the air filtration system and adjusting blower motor torque based upon a measured airflow or a measured static air pressure within the air filtration system.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to air flow in air filtration systems and more specifically to methods and systems for improving performance of air filtration systems. 
     Air filtration systems are driven by relatively constant speed motors, for example, induction motors configured as blowers or fans. There are disadvantages to such a system. In one example, as air filters within the system become clogged with debris, a higher static pressure within the air filtration system develops and the induction motor is unable to deliver a satisfactory airflow. However, with clean filters there is a low static pressure and the induction motor delivers a high airflow, perhaps more than desired for the application. In addition, when known air filtration systems are part of a Heating Ventilation and Air Conditioning (HVAC) system, which typically includes a blower or fan, air flow levels through the air filtration system portion of the HVAC system cannot be tracked with the air flow levels through the HVAC portion of the system. In such a system, where two blower motors are operating independently, air pressure differences and airflow problems throughout the system result. 
     It would be desirable to have an air filtration system where the amount of airflow in the air filtration system is controlled using a control system used to adjust the operation of the blower motor. In such a system it would be further desirable that the air filtration blower motor tracks the operation of a HVAC system blower motor. It would be further desirable to make air filtration systems more efficient by using variable speed motors as blowers rather than constant speed induction motors. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is, in one aspect, a method for improving performance in an air filtration system. The method includes monitoring performance of a blower motor in the air filtration system and adjusting blower motor torque based upon the measured blower motor performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a drawing of one embodiment of an air filtration system; 
     FIG. 2 is a drawing of one embodiment of a heating, ventilation and air conditioning (HVAC) system; and 
     FIG. 3 shows an exemplary embodiment of a motor control system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a drawing of one embodiment of an air filtration system  10  configured to ventilate a space  12 . Included in system  10  are a control system  14 , a blower motor  16 , a filter  18  and an air flow path  20 . Control system  14  is configured with a microprocessor and memory containing a control program and is contained within motor  16 . Motor  16  together with control system  14  are configured to maintain a constant airflow by varying the torque of blower motor  16  based upon sensed changes in motor speed due to pressure fluctuations in air flow path  20 . Control system  14  is further configured to monitor air flow, static air pressure, temperature or any other parameter relative to ventilation. 
     Pressure and airflow through system  10  typically varies due to a level of clogging of filter  18 . As stated above, control system  14  is configured to adjust torque of motor  16  to maintain a constant airflow through system  10 . As filter  18  becomes clogged with dust and debris, maintaining a constant airflow through system  10  dictates an increase in the torque of blower motor  16 . When filters  18  are replaced, pressures are reduced in system  10  and airflow through filter  18  is mostly unrestricted thereby necessitating a decrease in torque of motor  16  to maintain constant airflow in system  10 . In an alternative embodiment, control system  14  is configured to adjust speed of blower motor  16  to maintain a constant air pressure in system  10 . In another alternative embodiment, temperature is monitored in ventilated space  12  and motor  16  is configured to adjust speed to maintain a constant temperature in system  10 . 
     FIG. 2 is a drawing of one embodiment of a heating, ventilation and air conditioning (HVAC) system  30  configured to heat or cool a space  32 . Included in system  30  are a thermostat  34 , a blower motor  36 , a filter  38 , a heating and cooling source  40 , a HVAC blower  42  and an air flow path  44 . Motor  36  includes a motor controller  46  which is configured in one embodiment with a microprocessor and memory containing a control program. Motor controller  46  is further configured to maintain a constant airflow by varying torque of blower motor  36  based upon sensed pressure changes in airflow path  44 . Such pressure changes are, in one embodiment, caused by a changing fan speed of HVAC blower  42 . By sensing pressure changes, blower motor  36  is able to track the operation of HVAC motor  42 . Motor controller  46  is also configured to be electrically connected to thermostat  34  which controls turning off and on of heating and cooling source  40 . The selection of heating, cooling or fan only for heating and cooling source  40  using thermostat  34 , implies a selection of fan speed for HVAC blower  42 . Higher fan speeds are typically used for heating and cooling, while a lower fan speed is used for fan only to circulate air throughout system  30 . 
     Another source of pressure and airflow changes in system  30  is due to a level of clogging of filter  38 . In one embodiment, motor controller  46  is further configured to adjust the torque of motor  36  to maintain a constant airflow through system  30 . As filter  38  becomes clogged with dust and debris, maintaining a constant airflow through system  30  dictates an increase in the torque of blower motor  36  which is set by controller  46 . When filters  38  are replaced, pressures are reduced in system  30  and airflow through filter  38  is mostly unrestricted thereby allowing a decrease in motor speed as determined by controller  46 . In either scenario, blower motor  46  continues to track operation of HVAC blower  42  to maintain constant airflow through system  30 . Presence of a filter  50  at HVAC blower motor  42 , does not affect operation as described above or below. Pressures due to filter  50  clogging are still a cause of blower motor  36  torque changes and cause blower motor torque increases or decreases to maintain constant airflow. 
     Thermostat  34 , in one embodiment, is configured as a system controller. In such an embodiment, motor controller  46  is electrically connected to thermostat  34  and configured to receive information from thermostat  34  regarding operation and performance of system  30 , as thermostat  34  controls operation of heating and cooling source  40  and HVAC blower motor  42 . Therefore, thermostat  34  is configured to communicate to motor controller  46  whether system  30  is to be configured for heating, cooling, or for fan only. System  30  includes HVAC blower motor  42  which operates at higher speeds in a heating or cooling mode than when in a fan only mode. Blower motor  36  is configured to track operation of HVAC blower motor  42  to maintain a higher volume of air flow in system  30  when in a heating or cooling mode and a lower volume of air flow when in a fan only mode. Motor controller  46  can be configured for the monitoring of air flow, static air pressure, temperature or any other parameter relative to heating, ventilation and air conditioning. 
     In alternative embodiments, controller  46  is configured to adjust the speed of blower motor  36  to maintain a constant air pressure or a constant temperature in system  30 . In another alternative embodiment, controller  46  and blower motor  36  are configured to monitor and maintain a constant motor torque. 
     Air flow control schemes, as described in FIGS. 1 and 2, facilitate determination of a useful life of filters for the environment of a particular application. By measuring airflow, or alternatively, a motor torque or air pressure required to maintain a constant airflow, it is determined when a filter  18  (shown in FIG. 1) or a filter  38  should be replaced. As a system such as system  10  or system  30  determines that a filter requires replacement, a user is notified. In one embodiment, such as the embodiment shown in FIG. 2, motor controller  46  is configured to notify thermostat  34 , which is configured as a system controller, that a filter requires replacement. In alternative embodiments notification to the user are visual indicators, for example, a light emitting diode, or audio indicators, for example, a buzzer which are controlled by controllers  14  and  46  (shown in FIGS. 1 and 2 respectively). 
     Blower motors  16  and  36  can be any electrical motor capable of varying torque or speed, such as an electronically commutated motor. FIG. 3 shows an exemplary embodiment of a motor control system  60  according to one embodiment of the present invention such as ventilation system  10  (shown in FIG. 1) or HVAC system  30  (shown in FIG.  2 ). System  60  includes an interface circuit  62  electrically connected to a motor controller  64  and a system thermostat  66 . Motor controller  64  interprets information from interface circuit  62  and applies the interpreted operation information to motor  68  which operates a blower  70 . Information from interface circuit  62  are motor control signals, in one embodiment, motor controller  64  is a pulse width modulation controller including a microprocessor (not shown) programmed to control an electronically commutated motor. In another embodiment, the motor is controlled by a 24 VAC signal. Motor controller  64  receives signals from interface circuit  62  and thereby controls an amount of pulse width modulation applied to motor  68 . Motor controller  64  supplies motor status information to interface circuit  62  with motor feed back signals, for example, motor speed, motor torque, or airflow. Motor power signals  70  also are routed through controller  64 . 
     Interface circuit  62  is controlled by system thermostat  66 . In one embodiment, thermostat  66 , is set to one of, for example, heat, cool, or fan only, The settings of thermostat  66  determine which signal or signals are applied to interface circuit  62 , which in turn, determines the control signals sent from interface circuit  62  to motor controller  64  as described above. 
     The term microprocessor, as used herein, refers to microprocessors, microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), logic circuits, and any other circuit or processor capable of executing a program stored in memory. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.