A Low-Impedance Uninterruptible Power Technology for Nonlinear Critical Loads

New-generation mainframe computer complexes serving time-critical industrial and commercial users have introduced new problems for facilities engineers. Harmonic currents induced by switching computer power supplies badly distort the output waveform of high-impedance power sources. The resultant source current output will typically be out of required tolerance and can directly relate to unwanted voltage drops, data inaccuracies, and impaired load reliability. Conventional uninterruptible power supply systems offer load voltage continuity but suffer a trade-off in extremely high impedance compared to utility. This trade-off may no longer be well tolerated. A new UPS technology that demonstrates dramatically lower input-to-output impedance than was possible formerly will be evaluated. The system is based primarily on a unique rotating device employing a common stator for both motor and generator functions. Data will be presented on system reliability, efficiency, load isolation, and current-voltage dynamics.