Faculty Development with NASA/ASEE Summer Programs Leads to Enhanced EET Curriculum

Journal of Engineering Technology, Fall 2007 by Fox, Harry W

Abstract

This paper describes research experiences spanning two consecutive, summer ten-week periods (in 2004 and 2005) at the NASA Glenn Research Center by an electronics engineering technology faculty member. Several types of electronic inverters were investigated using computer models and testing of actual hardware to identify sources of power loss, and to determine methods for maximizing operating efficiency. Some technologies learned and used during the research experiences have been transferred to the classroom through modifications to senior-level courses in the Electronics Engineering Technology program.

I. Introduction

Opportunities for faculty development have been provided by ASEE and NASA in die form of ten-week summer programs at various NASA research centers for a number of years. At the Glenn Research Center (GRC) in Cleveland, Ohio, these programs were called Summer Research Opportunities in 2005, but they were called Summer Faculty Development Programs in prior years.These research programs are open to faculty in undergraduate engineering technology programs and provide a unique opportunity for faculty professional growth.

One such faculty research experience at the NASA Langley Research Center by a mechanical engineering technology faculty member was recentiy described.1-2 In this case the summer experience not only resulted in faculty professional growdi, but it also impacted on curriculum development by leading to the modification of an advanced manufacturing processes course and to the organization of special seminars. Of course, a number of other opportunities for professional development also exist for developing skills of faculty beyond the classroom, which include conferences, workshops, continuing education, on-die-job training, industrial internships, and consulting. 3,4,5

This paper describes research experiences during two summer ten-week periods (in 2004 and 2005) at the NASA Glenn Research Center by an electronics engineering technology faculty member. Each summer, the research involved investigating power losses in the operation of several types of electronic inverters used in diree-phase motor drives. During the first year (in 2004), computer simulations of inverter operation were developed and used to identify sources of power loss, and to evaluate mediods for maximizing operating efficiency. During the second year (in 2005), a prototype inverter was redesigned for reduced power losses, and tests were performed to quantify the improved efficiency. Each year, knowledge gained from the research experiences in the areas of power electronics and motor drives was transferred to the classroom tiirough modifications to courses in the EET program. These changes are also described in this paper.

II. Program Development

Much of the ongoing work at the GRC involves power conversion for space applications.The Advanced Electrical Systems Branch is a group that has been working on flywheel development for power conversion in space. This group sponsored the summer internships described in this paper.

During the first summer, the assigned task was to identify and recommend improvements to the electrical power converter (inverter), which is a part of the flywheel energy storage system, that would lead to increased operating efficiency. The approach was to model and simulate the existing converter using PSpice. A brief analysis of the resonant DC link converter was conducted to evaluate die converter for possible use as a power inverter.

During the second summer, the assigned task was to investigate a potentially more efficient inverter design, one that featured reverse conduction of the power MOSFET switches in the inverter. The assignment was to build and test a prototype half-bridge circuit that could be used as a building block in a flywheel inverter design.While searching for suitable parts for the prototype, suppliers of spacequalified parts for low-earth-orbit (LEO) missions were to be identified and tabulated for future use.

After the work at GRC, when the EET program curriculum was reviewed, it became clear that a broader coverage was needed in three academic areas: power electronics, advanced electronics, and control systems. For example, the power electronics course should cover the switching topologies of DC-DC conversion and DC-AC conversion (inverters). Also, more emphasis should be placed on BJT, FET (and possibly IGBT) switching circuits, operating at 100 KHz and higher frequencies, with less emphasis on SCR/ triac switching circuits. Motor drives are still important, but today's drives are higher frequency, and they are three-phase as well as single-phase. As another example, the control systems course needs to cover broader areas, such as fluids, heat transfer, and other processes, not just motor drives.

This work and the related curriculum improvements have an impact on a number of practical-application areas that are of interest to many (if not all) involved in power electronics.These areas include: