Benefits of system-oriented IGBT module design for high power inverters

Although today IGBT modules with blocking voltages up to 6500 V are available there are many applications that require the design of inverters with ratings close to or even beyond 1 MVA with 1200 V or 1700 V devices. The requirement to connect to the low voltage grid, system requirements for high switching frequency or voltage limits for associated system components may restrict the use of higher voltage inverters. On the other hand using lower voltage devices may result in lower cost because these devices are manufactured in larger quantities. Typical applications for such inverters are industrial variable speed drives, UPS-systems, heavy duty commercial vehicles as well as grid connection of microturbines or renewable energy systems like windmills or large solar farms. Designing power electronic circuits to switch currents in the range of several 1000 A within fractions of a microsecond is a demanding task for every engineer and requires a sound knowledge how to transform the implications of Maxwells laws into blueprints for busbars. Paralleling of smaller units helps to minimize stray inductances but unfortunately creating the new task of ensuring proper current sharing. Beside these technical challenges the power electronic designer is more and more faced with cost targets difficult to meet. In the beginning of power electronics, with the power semiconductor devices being the biggest item in the quantity survey, it was wise to address this just by trying squeeze as much current out of it as possible. Today with power semiconductors getting less expensive and other components raising in cost it may be advantageous to optimize in a different way.