Optimizing and implementing the switching of motor loads to backup power

Current and electromagnetic moments of synchronous and asynchronous motors need to be below the starting values when such motors are self-starting after triggering a high-speed automatic transfer switch; this is the subject matter of this paper. A mathematical model is applied herein to find the range of permissible angle of backup power fed to asynchronous and synchronous motors exposed to short-term power deviations; the range is a function of the angle between the residual voltage of the main power supply and the voltage of the backup. The paper further proposes methods of switching to backup power that keep the currents and electromagnetic moments of self-starting motors below the starting values; these methods can be implemented in high-speed automatic transfer switch (ATS) microprocessors. Bench testing and mathematical modeling prove the proposed methods effective.