Reduced Rated Adjustable Speed Drives Starting for High Power Applications

There is a large installed base of very large motors above 10 MW that have been started with across the line starters or breakers rated 6.9 kV to 13.8 kV. With changes in the power utility networks and more stringent voltage drop allowances, they may no longer be allowed to start across the line, but starting torque requirements could prevent reduced voltage starting. One option is to utilize reduce rated adjustable speed drives for either induction or synchronous motors to bring the motor up to speed. This paper will describe how to size an adjustable speed drive for starting duty applications. The same sizing requirements can be applied for new applications as well as complete retrofits of an older engines and turbines with an electric motor.