Power Transfer Unit

摘要

Switching of three phase wye power can be efficiently completed without synchronization between two or more energy sources. The absence of synchronism can be overcome by switching one source off and then in a very short time frame restoring the power from the second power source. The duration of the outage can be controlled and minimized so that the load never loses energy long enough to cause an operational problem. The interruption time period in this description is limited to about 100 microsecond span; long enough to avoid interaction between the separate power sources, yet short enough to be transparent to the load. Electrical transfer of loads between power sources may be controlled precisely if the switching is accomplished using solid state electronic devices. The power transfer unit (PTU) allows power contractors to transfer power from a number of power sources (14, 14') in a controlled manner to minimize disruption at the load (12). The PTU utilizes a logic controlled electronic switch (24) in parallel with the contacts of a power control relay (10). The combination of an electronically controlled switch and an electromechanical relay provide precise switch timing with minimum power dissipation.