Variable speed fan motor control for forced air heating/cooling system
First Claim
1. A control system for controlling the speed of a fan motor for a forced air conditioning system to vary motor speed during operation of the system to minimize temperature stratification and heating or cooling exchange losses in said air conditioning system, said control system comprising:
- a first temperature sensor disposed in a return air flowpath of air returning from an enclosed space to said air conditioning system;
a second temperature sensor located downstream of at least one heat exchanger of said air conditioning system for measuring the air temperature at the location of said second sensor compared with the air temperature at the location of said first sensor;
a ramp circuit for producing a variable voltage output signal dependent on the difference in temperatures sensed by said first and second sensors; and
a pulse generator circuit connected to said ramp output circuit and to a power output circuit for controlling the speed of said motor, said pulse generator circuit being operable to vary a pulse signal to said power output circuit as a function of the output signal of said ramp circuit to vary the speed of said fan motor in accordance with the difference in temperatures sensed by said first and second sensors.
0 Assignments
0 Petitions
Accused Products
Abstract
A fan motor speed control system for controlling the fan motor speed of an air conditioning system includes a power output circuit including a power triac which is turned on and off by an opto-isolator connected to a pulse generator circuit for varying an AC voltage waveform imposed on the fan motor. The pulse generator circuit is connected to heating and cooling ramp circuits and a minimum speed circuit to provide a variable voltage signal imposed on the pulse generator circuit corresponding to the temperature difference sensed by a return air sensor and a heating or cooling sensor or by separate heating and cooling sensors disposed adjacent respective heating and cooling heat exchangers of the air conditioning system. An adjustable minimum speed circuit and a cutoff circuit are provided to control motor minimum speed or motor shutoff when a predetermined minimum speed is reached to prevent motor bearing failure or overheating. Sensor protection circuits in the control system operate to drive the motor to full speed if any of the temperature sensors experience an open or short circuit condition. The control system circuit maximizes air conditioning system efficiency by capturing additional heating or cooling effect, reduces noise associated with motor startup and shutdown, and reduces rapid change in the sensed temperature in the air conditioned space during motor startup and shutdown.
-
Citations
18 Claims
-
1. A control system for controlling the speed of a fan motor for a forced air conditioning system to vary motor speed during operation of the system to minimize temperature stratification and heating or cooling exchange losses in said air conditioning system, said control system comprising:
-
a first temperature sensor disposed in a return air flowpath of air returning from an enclosed space to said air conditioning system;
a second temperature sensor located downstream of at least one heat exchanger of said air conditioning system for measuring the air temperature at the location of said second sensor compared with the air temperature at the location of said first sensor;
a ramp circuit for producing a variable voltage output signal dependent on the difference in temperatures sensed by said first and second sensors; and
a pulse generator circuit connected to said ramp output circuit and to a power output circuit for controlling the speed of said motor, said pulse generator circuit being operable to vary a pulse signal to said power output circuit as a function of the output signal of said ramp circuit to vary the speed of said fan motor in accordance with the difference in temperatures sensed by said first and second sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A control system for controlling the speed of a fan motor for a forced air conditioning system to vary motor speed during operation of the system to minimize temperature stratification and heating or cooling exchange losses in said air conditioning system, said control system comprising:
-
a first temperature sensor disposed in a return air flowpath of air returning from an enclosed space to said air conditioning system;
a second temperature sensor located downstream of a first heat exchanger of said air conditioning system for measuring the air temperature at the location of said second sensor compared with the air temperature at the location of said first sensor;
a third temperature sensor located downstream of a second heat exchanger of said air conditioning system for measuring the air temperature at the location of said third sensor compared with the air temperature at the location of said first sensor;
a ramp circuit for producing a variable voltage output signal dependent on the difference in temperatures sensed by said second or third sensors with respect to said first sensor; and
a pulse generator circuit connected to said ramp circuit and to a power output circuit for controlling the speed of said motor, said pulse generator circuit being operable to vary a pulse signal to said power output circuit as a function of the output signal of said ramp circuit to vary the speed of said fan motor in accordance with the difference in temperatures sensed by said sensors. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
-
Specification