System and methods for controlling a draft inducer to provide a desired operating area

A method of operating a system for driving a rotatable component in response to an external signal corresponding to a desired motor current, the system including a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly in driving relation to the rotatable component, the system having an operating region outside of which excessive heat may be generated by the system, the method comprising:

• controlling power switching devices in response to a motor control signal for selectively connecting a power supply to the windings to provide a motor current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed;
• sensing the speed of the motor and generating a tachometer signal representative of the motor operating speed;
• defining a speed/current region of desired motor operation by a reference speed and a maximum current which is a function of the motor operating speed as represented by the tachometer signal;
• comparing the motor operating speed as represented by the tachometer signal to the reference speed to determine when the motor operating speed is greater than or equal to the reference speed and to determine when the motor operating speed is less than the reference speed;
• comparing the desired motor current as represented by the external signal to the maximum current to determine when the desired maximum current is greater than or equal to the maximum current;
• generating the motor control signal in response to the external signal and the tachometer signal for controlling the power switching devices so that a current corresponding to the desired motor current is provided to the windings by the power switching devices when the motor operating speed is greater than or equal to the reference speed;
• and
• generating the motor control signal in response to the external signal and the tachometer signal for controlling the power switching devices so that a current corresponding to the maximum current is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed and the desired motor current is greater than or equal to the maximum current thereby maintaining operation of the motor within the defined speed/current region whereby excessive heat is prevented from being generated by the system.

A heating, ventilation and air conditioning system comprising:

• a fan for inducing a draft through a vent;
• a motor for driving the fan having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly in driving relation to the fan, the motor having an operating region outside of which excessive heat may be generated by the motor;
• power switching devices responsive to a motor control signal for selectively connecting a power supply to the windings to provide a motor current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed;
• a speed sensing circuit for generating a tachometer signal representative of the motor operating speed;
• a pressure sensor for generating a pressure signal representative of a minimum pressure in the vent and corresponding to a desired motor current at the motor operating speed;
• and
• a controller comparing the motor operating speed as represented by the tachometer signal to a reference speed and comparing the desired motor current as represented by the pressure signal to a maximum current which is a function of the motor operating speed and responsive to the pressure signal and the tachometer signal for generating the motor control signal to control the power switching devices, the controller generating the motor control signal so that a current corresponding to the desired motor current is provided to the windings by the power switching devices when the motor operating speed is greater than or equal to the reference speed, the controller generating the motor control signal so that a current corresponding to the maximum current is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed and the desired motor current is greater than or equal to the maximum current thereby maintaining operation of the motor within a speed/current region defined by the reference speed and the maximum current whereby excessive heat is prevented from being generated by the motor.

A method of operating a heating, ventilating, and/or air conditioning system having a fan for inducing a draft through a vent and a motor for driving the fan, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly in driving relation to the fan, the motor having an operating region outside of which excessive heat may be generated by the motor, the method comprising:

• controlling power switching devices in response to a motor control signal for selectively connecting a power supply to the windings to provide a motor current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed;
• sensing the speed of the motor and generating a tachometer signal representative of the motor operating speed;
• sensing pressure in the vent and generating a pressure signal representative of a minimum pressure in the vent and corresponding to a desired motor current at the motor operating speed;
• defining a speed/current region of desired motor operation by a reference speed and a maximum current which is a function of the motor operating speed as represented by the tachometer signal;
• comparing the motor operating speed as represented by the tachometer signal to the reference speed to determine when the motor operating speed is greater than or equal to the reference speed and to determine when the motor operating speed is less than the reference speed;
• comparing the desired motor current as represented by the pressure signal to the maximum current to determine when the desired maximum current is greater than or equal to the maximum current;
• generating the motor control signal in response to the pressure signal and the tachometer signal for controlling the power switching devices so that a current corresponding to the desired motor current is provided to the windings by the power switching devices when the motor operating speed is greater than or equal to the reference speed;
• and
• generating the motor control signal in response to the pressure signal and the tachometer signal for controlling the power switching devices so that a current corresponding to the maximum current is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed and the desired motor current is greater than or equal to the maximum current thereby maintaining operation of the motor within the defined speed/current region whereby excessive heat is prevented from being generated by operation of the motor.

A motor and control system having an operating region outside of which excessive heat may be generated by the motor, said motor and control system comprising:

• a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence;
• power switching devices responsive to a motor control signal for selectively connecting a power supply to the windings to provide a motor current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed;
• a speed sensing circuit for generating a tachometer signal representative of the motor operating speed;
• and
• a controller comparing the motor operating speed as represented by the tachometer signal to a reference speed and comparing a desired motor current at the motor operating speed as represented by an external signal to a maximum current which is a function of the motor operating speed and responsive to the external signal and the tachometer signal for generating the motor control signal to control the power switching devices, the controller generating the motor control signal so that a current corresponding to the desired motor current is provided to the windings by the power switching devices when the motor operating speed is greater than or equal to the reference speed, the controller generating the motor control signal so that a current corresponding to the maximum current is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed and the desired motor current is greater than or equal to the maximum current thereby maintaining operation of the motor within a speed/current region defined by the reference speed and the maximum current whereby excessive heat is prevented from being generated by the motor.

A method of operating a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence, the motor having an operating region outside of which excessive heat may be generated by the motor, the method comprising:

• controlling power switching devices in response to a motor control signal for selectively connecting a power supply to the windings to provide a motor current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed;
• sensing the speed of the motor and generating a tachometer signal representative of the motor operating speed;
• defining a speed/current region of desired motor operation by a reference speed and a maximum current which is a function of the motor operating speed as represented by the tachometer signal;
• comparing the motor operating speed as represented by the tachometer signal to the reference speed to determine when the motor operating speed is greater than or equal to the reference speed and to determine when the motor operating speed is less than the reference speed;
• comparing a desired motor current at the motor operating speed as represented by an external signal to the maximum current to determine when the desired maximum current is greater than or equal to the maximum current;
• generating the motor control signal in response to the external signal and the tachometer signal for controlling the power switching devices so that a current corresponding to the desired motor current is provided to the windings by the power switching devices when the motor operating speed is greater than or equal to the reference speed;
• and
• generating the motor control signal in response to the external signal and the tachometer signal for controlling the power switching devices so that a current corresponding to the maximum current is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed and the desired motor current is greater than or equal to the maximum current thereby maintaining operation of the motor within the defined speed/current region whereby excessive heat is prevented from being generated by operation of the motor.

In a heating, ventilating and air conditioning system having a fan driven by a motor for inducing a draft through a vent, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence for producing an electromagnetic field for rotating the rotatable assembly at a motor operating speed, the rotatable assembly in driving relation to the fan, the motor having an operating region outside of which excessive heat may be generated by the motor and/or a controller for the motor, the controller comprising:

• a commutating circuit responsive to a pressure signal and a tachometer signal for generating a motor control signal, said pressure signal being representative of a minimum air pressure in the vent and corresponding to a desired motor current at the motor operating speed and said tachometer signal being representative of the motor operating speed;
• a comparing circuit comparing the motor operating speed as represented by the tachometer signal to a reference speed, said motor control signal controlling power switching devices for selectively connecting a power supply to the windings to provide a current corresponding to the desired motor current to the windings in the preselected sequence when the motor operating speed is greater than or equal to the reference speed;
• and
• a current limit circuit for limiting the motor control signal so that a current corresponding to a maximum current less than or equal to the desired motor current is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed thereby maintaining operation of the motor within a speed/current region defined by the reference speed and the maximum current whereby excessive heat is prevented from being generated by the motor and/or controller.

In a heating, ventilating and air conditioning system having a fan driven by a motor for inducing a draft through a vent, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed, the rotatable assembly in driving relation to the fan, the motor having an operating region outside of which excessive heat may be generated by the motor, a method for controlling the motor comprising the steps of:

• generating a motor control signal in response to a pressure signal and a tachometer signal, said pressure signal being representative of a minimum air pressure in the vent and corresponding to a desired motor current at the motor operating speed and said tachometer signal being representative of the motor operating speed;
• comparing the motor operating speed as represented by the tachometer signal to a reference speed;
• controlling power switching devices in response to the motor control signal for selectively connecting a power supply to the windings to provide a current corresponding to the desired motor current to the windings in the preselected sequence when the motor operating speed is greater than or equal to the reference speed;
• and
• limiting the motor control signal so that a current corresponding to a maximum current less than or equal to the desired motor current and which is a function of the motor operating speed is provided to the windings by the power switching devices when the motor operating speed is less than the reference speed thereby maintaining operation of the motor within a speed/current region defined by the reference speed and the maximum current whereby excessive heat is prevented from being generated by operation of the motor.

A system for driving a rotatable component in response to an external signal corresponding to a desired motor torque, said system having an operating region outside of which excessive heat may be generated by the system, said system comprising:

• a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly in driving relation to the rotatable component;
• power switching devices responsive to a motor control signal for selectively connecting a power supply to the windings to provide current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly;
• a speed sensing circuit for generating a tachometer signal representative of the speed of the motor;
• and
• a controller comparing the speed of the motor as represented by the tachometer signal to a reference speed and comparing the desired motor torque as represented by the external signal to a reference torque which is a function of the speed of the motor and responsive to the external signal and the tachometer signal for generating the motor control signal to control the power switching devices, the controller generating the motor control signal so that a desired current corresponding to the desired motor torque is provided to the windings by the power switching devices when the speed of the motor is greater than or equal to the reference speed, the controller generating the motor control signal so that a maximum current corresponding to a the reference torque is provided to the windings by the power switching devices when the speed of the motor is less than the reference speed and the desired motor torque is greater than or equal to the reference torque thereby maintaining operation of the motor within a speed/torque region defined by the reference speed and the reference torque whereby excessive heat is prevented from being generated by the system.

A method of operating a system for driving a rotatable component in response to an external signal corresponding to a desired motor torque, the system including a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly in driving relation to the rotatable component, the system having an operating region outside of which excessive heat may be generated by the system, the method comprising:

• controlling power switching devices in response to a motor control signal for selectively connecting a power supply to the windings to provide current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly;
• sensing the speed of the motor and generating a tachometer signal representative thereof;
• defining a speed/torque region of desired motor operation by a reference speed and a reference torque which is a function of the speed of the motor as represented by the tachometer signal;
• comparing the speed of the motor as represented by the tachometer signal to the reference speed to determine when the speed of the motor is greater than or equal to the reference speed and to determine when the speed of the motor is less than the reference speed;
• comparing the desired motor torque as represented by the external signal to the reference torque to determine when the desired motor torque is greater than or equal to the reference torque;
• generating the motor control signal in response to the external signal and the tachometer signal for controlling the power switching devices so that a desired current corresponding to the desired motor torque is provided to the windings by the power switching devices when the speed of the motor is greater than or equal to the reference speed;
• and
• generating the motor control signal in response to the external signal and the tachometer signal for controlling the power switching devices so that a maximum current corresponding to the reference torque is provided to the windings by the power switching devices when the speed of the motor is less than the reference speed and the desired motor torque is greater than or equal to the reference torque thereby maintaining operation of the motor within the defined speed/torque region whereby excessive heat is prevented from being generated by the system.