Title:  Condition Monitoring of High Efficiency Heating, Ventilation and Air Conditioning System

Committee:

Dr. Thomas Habetler, ECE, Chair , Advisor

Dr. Maryam Saeedifard, ECE

Dr. Ron Harley, ECE

Dr. Stephen Fedigan, TI

Dr. Sheldon Jeter, ME

Abstract: 

Energy consumption has increased rapidly in recent decades. This has elevated concerns regarding an energy crisis and heavy environmental impacts. This research focuses on increasing energy efficiency in HVAC (Heating, Ventilation and Air conditioning) systems. The air handler in the HVAC system has electrical and mechanical components that can experience problems from time to time. Airflow blockage and a failure of a blower motor are two of the most common problems in air handlers. Airflow blockage is detected utilizing a current based condition monitoring method. The static pressure of the fan blade, load torque and fan motor speed are analyzed to solve this problem. For most air handlers, the unbalanced load of the blower wheel is created by the unevenly distributed contaminants on the blades. The traditional current based condition monitoring method is conducted to a BLDC (Brushless DC) fan motor followed by a stray flux spectrum analysis, which increases the reliability in detecting an unbalanced load condition. Static eccentricity and dynamic eccentricity are two of the main faults in the rotor of a BLDC motor. An improved method in detecting static eccentricity is proposed based on the comparison between the positive sequence current and negative sequence current. Finally, a current based nonintrusive condition monitoring method is established for refrigerant level detection. A thermal model of a compressor is analyzed under insufficient refrigerant level conditions to explore the mathematical relationship between refrigerant level and stator winding resistance. The undercharged detection algorithm is proposed with a detailed analysis of temperature threshold settings. This algorithm can be easily implemented to the original HVAC system to increase the system reliability and efficiency and to reduce the labor cost of refrigerant level detection.