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An alternate power supply guarantees the performance of loads during voltage disturbances in the normal supply. It is proposed to implement a quick change over of the power supply of single-phase electronic loads from the faulty phase to a healthy phase in a 3-phase system. Super capacitors maintain the dc voltage during the period of disturbance. A zigzag transformer may also be used to rebuild a balanced 3phase load voltage by isolating the faulty phase from the load. Both the 3-phase and single-phase loads may be supplied with the rated voltage during the period of disturbance. Use of a static transfer switch reduces the change over time to 0.02 second.Index Terms--Short-time power interruption, power failure, voltage sag, alternate power supply, super capacitor, zigzag transformer, zero sequence impedance Dr. K. P. Basu (M'99 and SM'02) received his