In my earlier blog on the 787, I talked about the dramatic increase (5X) in electrical power on board the aircraft versus its predecessor due to increased demand. With all that power, the weight of the electrical power system is sure to go up and at some point, the electrical power system weight will drive decisions and compromises in aircraft design. A step change in technology is needed to overcome the weight challenge.
Current power electronic components are silicon (Si) based and as power devices are forced to achieve higher efficiency, the silicon core is operating closer to its temperature limit. Extra cooling packaging is required to maintain reliability, which becomes a key driver of the weight increase. A breakthrough in reduced cooling requirements is anticipated with the introduction of silicon carbide (SiC) based devices. Key advantages of SiC are that they can operate at higher temperatures (more than 50% higher than Si-based devices) and at faster switching speeds, especially at high voltage (> 600V). However, fundamental challenges associated with reliability and yield of the SiC devices are preventing mass adoption in many markets.
Many leading power electronics manufacturers are focusing on the SiC device area. Cree has launched the first commercial SiC-based MOSFET. The product’s performance is slightly better than Si-based devices, and more companies will join suit in the next two to three years with more capable devices. Why the focus? The industry is anticipating the next generation hybrid-electric and pure-electric vehicles to adopt SiC technology, making the vehicles more efficient than current generations. Companies are jockeying for a piece of this huge market.
GE is certainly not standing still on the sideline in SiC development. GE Aviation Systems, in collaboration with GE’s Global Research Center (GRC), has a an industry leading cooperative project with AFRL at Wright Patterson AFB to develop an advanced solid-state primary power distribution technology using Silicon Carbide (SiC) high power switches. GE also announced introduction of a new line of SiC-based power conversion devices at the 2011 Paris Air Show. GE anticipates that its proprietary SiC technology will be world class, addressing fundamental challenges of gate oxidation and switch reliability. Once the technology matures, we can imagine that the next generation of aircraft will have electrical power equipment that enables aircraft manufacturers to continue up the power curve without lumbering heavy electrical power systems.
Click here to see GE’s SiC MOSFET.
Click here to see lower switching loss of GE’s all SiC module vs. hybrid Si-SiC module.