Low cost three-phase emergency power supply

This paper demonstrates the analysis and the implementation of a three-phase supply to be used as an emergency power source, particularly for domestic and commercial applications. The system has been constructed in a modular form for easier maintenance; including a battery bank, an electronic battery charger, a DC chopper, a 3-ph multi-stepped inverter, an optional 3-ph low pass filter, an automatic transfer switch (ATS), a low power switched mode supply and a control unit generating the required gate signals. Such configuration validates the use of low-voltage low-frequency low-cost BJT transistors and transformers, hence reducing the overall cost. The ATS provides an off-line system operation to reduce its running cost and increase its lifetime. The overall system has been tested up to a 3-ph load of 9kW–380V–50Hz. Simulated results are matched with the corresponding practical results, showing the effectiveness of the system with higher efficiency, lower voltage regulation and more safe operation comparing to the conventional emergency electro-mechanical alternator.