Constant air flow control apparatus and method

Air handling apparatus for delivering a volume of air at a generally constant flow rate regardless of changes in the operating conditions of an environment with which the apparatus is used comprising:

• a blower for moving air from one point to another, and a blower motor for running the blower;
• switch means for controlling power supplied to the motor;
• sensing means for sensing the motor's operating speed;
• sensing means for sensing the current drawn by the motor;
• flow control means for establishing a desired air flow rate;
• and,
• processor means responsive to the sensed operating speed and motor current, and an input from the flow control means to determine a torque required by the motor to produce a desired air flow rate, the torque being determined as a function of the motor speed, the flow control means input, and speed, torque, pressure, and air flow characteristics of the blower, the calculated torque including an offset value, and the processor means including means responsive to the calculated torque and the motor current to produce a control signal supplied to the switch means to control application of a voltage to the motor for the motor to produce the calculated torque.

A method of controlling the operation of a blower motor in an air handling system to provide a desired flow rate of air which is substantially constant over a wide range of operating conditions comprising:

• sensing the current drawn by the motor and providing an output signal representative thereof;
• sensing the output speed of the motor and providing an output signal representative thereof:
• establishing a predetermined air flow rate and providing a flow rate signal representative thereof;
• processing the motor speed signal and flow rate signal to determine a torque required by the motor for the predetermined airflow rate, processing of the motor speed and flow rate signals including combining the values represented by the motor speed and flow rate signals with values representing the air flow, pressure, and speed characteristics of the blower, the torque value determined including an offset torque value;
• and
• generating a control signal and supplying the control signal to a switch means for the switch means to supply a voltage to the motor sufficient for the motor to produce the requisite torque;
• generating the control signal including combining the torque value with the value representing motor current to produce the control signal, controlling operation of said blower motor using said control signal maintaining a constant air flow rate in the system regardless of changes therein.

A method of controlling the operation of a blower motor used in an air handling system to provide a substantially constant air flow rate over a wide range of operating conditions, the

• blower having a predetermined set of operating characteristics to move the air, and the blower being operated by the blower motor to which a voltage is supplied, the method comprising:
• sensing a current dram by the motor and the motor's operating speed, and providing output signals representative thereof;
• establishing a desired air flow rate and providing a flow rate signal representative thereof;
• deriving a set of constant values representing the blower's operational characteristics torque/speed curves for the blower;
• processing the motor speed signal and flow rate signal to determine a torque required to be produced by the motor for the desired air flow rate, processing the motor speed and flow rate signals including calculating the required torque according to the equation
• torque=(K1*S*C)+(K2*S)+(K3*C)+K4,
• where S represents motor speed, C is the desired air flow rate, and K1-K4 are constants representing air flow, torque, pressure, and speed characteristics of the blower and are derived for the particular blower operated by the motor;
• generating a control signal which is a function of the calculated torque and the current drawn by the motor and supplying the control signal to a switch means which controls the voltage applied to the motor, the voltage to the motor in response to the control signal being sufficient for the motor to produce the calculated torque.

In a method of controlling the operation of a blower motor for an air handling system to provide a substantially constant air flow over a wide range of operating conditions, the method comprising operating a blower having a predetermined set of operating characteristics by a blower motor to which a voltage is supplied, sensing the operating speed and current of the motor and providing respective output signals representative thereof, and establishing a desired air flow rate and providing a flow rate signal representative thereof, the improvement comprising:

• processing the motor speed and flow rate signals to determine a torque required to be produced by the motor to produce the desired air flow rate to be produced by the blower;
• producing a control signal for operating the motor which is a function of the calculated torque and the sensed motor current;
• and,
• supplying the control signal to a switch means for the switch means to supply a voltage to the motor sufficient for the motor to produce the calculated torque.