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Motion System Design

SiC switches offer big power boost

Researchers at the Electric Power Research Institute (EPRI) have developed high-power switches made from silicon carbide (SiC) crystals. The 1-sq-cm devices represent a milestone in power and size that could significantly improve the performance of advanced power electronics used to control the bulk flow of electricity.

“As power electronics are incorporated into the power delivery system, utilities will be better able to exert control overpower flow and protect their customers from outages and other power quality problems,” says Clark Gellings, EPRI's VP for Innovation.

The new technology has an electronic structure that lets it support ten times higher voltage gradients and operate at higher temperatures than silicon. It also has a thermal conductivity three times higher than silicon - slightly better than copper. Because of these properties, SiC has the potential to provide devices with ten times the voltage limit of silicon and with two to three times the current density. The SiC switch, manufactured by Cree Inc., blocks 1,750 V and conducts 250 A, and operates up to 250°C junction temperature.

Commercialization of SiC technology wasn't possible for many years because of the quality of available SiC crystals. But recent R&D funding from the U.S. government has enabled researchers to increase the diameter of production wafers to 3 in. and drastically reduce the number of defects in the crystal. EPRI funded a demonstration project using the wafers in prototype power electronics devices. The reduction in defect density allows the devices to be larger than ever before.

This development in SiC wafer production means power electronic devices can be smaller, less costly, and have fewer parts than their silicon counterparts. Initially, this type of device will be used in motor drives for industrial plants and eventually in the thyristors of flexible ac transmission system devices that control power flow through high-voltage transmission lines.

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