Overview and Evolution of the LeRC PMAD DC Test Bed 929217

Since the beginning of the Space Station Freedom Program (SSFP), the Lewis Research Center (LeRC) has been actively involved in the development of electrical power system test beds to support of the overall design effort. Throughout this time, the SSFP Program has changed the design baseline numerous times, however, the test bed effort has endeavored to track these changes. Beginning in August 1989 with the baselining of an all DC System, a test bed was developed which supported this design baseline. However, about the time of the Test Bed's Completion in December 1990, the SSFP was again going through another design scrub known as Restructure.

This paper describes the LeRC PMAD DC Test Bed and highlights the changes that have taken place in the Test Bed configuration and design resulting from the SSFP Restructure Exercise in December 1990. These changes have principally included the reduction of primary power channel size with an accompanying reduction in the size of various power processing elements. In addition to the scrubbing of the channel size, a substantial reduction was made in the amount of flight software with the subsequent migration of these functions to ground control centers. The impact of these changes on the design of the power hardware, the controller algorithms and the control software along with a description of their current status is presented.

An overview of the testing that has been conducted with the test bed during the last year is also highlighted. These tests include investigations of stability and source impedance, primary and secondary fault protection, and performance of a rotary utility transfer device.

Finally, information is presented on the evolution of the test bed to support the verification and operational phases of the Space Station Freedom Program in light of these restructure scrubs.