Uninterruptable Power for Critical Loads

A description of the design and performance of high-power thyristor inverters for uninterruptable power systems is presented. These inverters have been designed to provide precisely regulated and continuous ac electrical power for critical loads, such as real-time data processing computers, air route traffic control centers, and industrial process control equipment. High reliability, over 80 000 hours MTBF, is achieved by utilizing a parallel redundant system configuration. Systems have been designed with ratings of up to 2000 kVA. Typical instantaneous voltage transient limits are plus 10 and minus 10 percent. Frequency tolerance is plus or minus one-half percent. Total harmonic distortion is less than 5-percent rms.