Reliability Comparison of Matrix and Other Converter Topologies M. ATEN, Member, IEEE G. TOWERS C. WHITLEY Smiths Aerospace Mechanical Systems—Flight Controls UK P. WHEELER, Member, IEEE J. CLARE, Senior Member, IEEE K. BRADLEY, Member, IEEE University of Nottingham Several rectifier-inverter and matrix converter topologies suitable for aerospace applications are compared, and their reliability is predicted. The military handbook MIL-HDBK-217F guidelines have been used to predictreliability. The matrix converter has several attractive features for aerospace applications such as potential size and weight savings. Although the matrix converter has a higher number of semiconductor switches, they are subjected to a lower voltage stress, which decreases their failure rate. This results in the reliability indicators of the different converter topologies being very similar. Manuscript received October 29, 2004; revised July 1, 2005; released for publication January 17, 2006. IEEE Log No. T-AES/42/3/884437. Refereeing of this contribution was handled by W. M. Polivka. This work was supported in part by the UK Department of Trade & Industry and Smiths Aerospace Mechanical Systems—Flight Controls, under the research program EDAAS (Electrically Driven Advanced Actuation Systems). Authors’ addresses: M. Aten, G. Towers, C. Whitley, Smiths Aerospace Mechanical Systems—Flight Controls, Wobaston Rd., Wolverhampton, WV9 5EW, UK; P. Wheeler, J. Clare, K. Bradley, Power Electronics, Machines and Control Group, School of Electrical and Electronic Engineering, University of Nottingham, Nottingham, NG7 2RD, UK, E-mail: (pat.wheeler@nottingham.ac.ul). 0018-9251/06/$17.00 c ° 2006 IEEE I. INTRODUCTION This paper describes reliability predictions that have been carried out for different converter drive topologies suitable for aerospace applications. Electrical power is consumed in aircraft by avionics, lighting, galleys, fans, and increasingly by entertainment systems. There is also a trend towards the implementation of the so-called “more electric aircraft” (MEA) using more electric power to drive aircraft subsystems that conventionally have been driven by a combination of mechanical, hydraulic, pneumatic, and electrical systems. The aircraft architecture consists of many optimized components, but there is scope for further optimization at a system level. As further improvements in the design of mechanical and hydraulic solutions reach the point of diminishing returns, the aerospace industry is looking for alternative methods [1, 2]. Integrated mechanical and electrical systems are sought to reduce overall system weight, volume, energy losses, and maintenance costs, resulting in lower operational costs, whereas the same or higher system reliability and safety must be achieved. Present flight control technology for civil or cargo aircraft is based on “fly by wire” (FBW) systems that use electrical signals originating from the cockpit to control hydraulically powered actuators [3]. A central hydraulic pump transfers hydraulic power to the flight control actuation systems, and to landing gear for deployment, retraction and braking, to engine actuation, and to thrust reversal systems. Electrical power, unlike hydraulic power, can be generated on demand allowing fuel cost reduction. Although hydraulic actuators tend to have higher power density than electrically powered actuators, the hydraulic infrastructure using pipes is heavier and less flexible than the use of electric cables [4, 5]. Electrically powered actuation is becoming more attractive due to technology advances in permanent magnet synchronous (brushless) motors with new magnetic materials, and motor drive controllers with improved power electronic semiconductors, and micro-electronic control circuits. Power electronic converters are required to control electrical power. They are necessary for motor drive controllers in electrically powered actuators, and can be used to convert variable frequency (360—800 Hz) in the next generation of civil aircraft to a constant frequency supply bus for various loads. As converter drives play an ever increasing role in safety critical aircraft systems, there is a clear need to predict and compare their reliability. The reliability of five different converter topologies has been analyzed using the military handbook for reliability prediction of electronic equipment MIL-HDBK-217F [6]. Although MIL-HDBK-217F has been criticized for being obsolete and pessimistic [7], it is still the most widely IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. 42, NO. 3 JULY 2006 867