Utilization of renewable energy has become the future trend in the trucking industry. Electrical power generated from renewable energy can replace part of the fuel usage. There is usually limited space for storing on-board battery. Thus, to better utilize the battery power, it becomes critical to have an efficient energy conversion device that can transfer energy from battery to amenities such as air conditioner, microwave, TV, mini refrigerator, etc. In this dissertation, a designed permanent magnet synchronous motor (PMSM) can be such energy conversion device for an electric Auxiliary Power Unit (APU) application, which will have a desired output power of 2 kW at 2 krpm, and maintain an efficiency greater than 90%. The design calls for good performance over a speed range of 1.5 krpm to 2.5 krpm. The current air conditioning system for automobile works only by "on" or "off" mode. For the heat mode, that means it is on with heat once the cabin temperature drops down to a level and off if the temperature rises back above that level. For the cool mode, that means it is on with cold air once the cabin temperature rises above a level, and off if the temperature drops back to that level. This is because the motor does not have the speed control functionality according to the temperature variation and people in the cabin do not feel much comfortable for that temperature change periodically as well as the inefficient energy consumption. With our novel technology, the designed motor can adjust its speed through the embedded system of our novel DC to AC inverter to provide a variable load. For example, with high efficiency, the fully charged battery sets (48 volts) can supply the electrical power and cooling to the cabin for about 10 hours without recharging using the main engine. Copper loss is the most significant part of all the losses in low speed electric machines. Reducing the copper loss is the key to build highly efficient machine. We use copper wires with the current density lower than traditional design which result in large cross section of the wire and thus reduce the copper loss and improve the efficiency. This also makes thermal management easier and reduces the need to use active cooling methodologies (such as fan, liquid cooling or spray cooling); and hence the overall power density of the whole system (including cooling devices) will not decease much. In traditional machine design, the torque angle is designed to be in the range of 15 to 30 degrees at the rated power and speed. In our high efficiency motor design, we propose to use much lower torque angle of 2 to 15 degrees at the rated power and speed. Such design can effectively increase the overload power handling capability and efficiency. Besides, small torque angle will result in large airgap size and increased thickness of the permanent magnets. Large airgap helps to reduce the windage loss of the machine and generates a lot less mechanical noise based on our design experience. Increased thickness of the permanent magnets helps to avoid the demagnetization. As the technology of advanced micro-controller develops, fast response power electronic devices can be used in the motor controller. A novel design of DC to AC inverter with the field oriented control scheme and sliding mode observer algorithm for driving the designed motor is developed. The inverter has the capability of driving the motor with its output power at 2 kW.


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Graduation Date





Wu, Thomas X.


Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science


Electrical Engineering and Computer Engineering

Degree Program

Electrical Engineering









Release Date


Length of Campus-only Access

5 years

Access Status

Doctoral Dissertation (Open Access)