System for switching a load between two sources

Claim 1

A switching system for bi-directional switching of a load between first and second independent, asynchronous a-c sources comprising: first bi-state switching means; second bi-state switching means in series with said first switching means and operable with said first switching means to connect said first source to said load when said first and second switch means are in one state; third bi-state switching means; fourth bi-state switching means in series with said third switching means and operable with said third switching means to connect said second source to said load when said third and fourth switching means are in one state; fifth bi-state switching means; a first bi-state actuator being coupled to said first, third and fifth switching means and being operable to control the state of said first, third and fifth switching means; a second bi-state actuator being coupled to said second and fourth switching means and being operable in response to said fifth switching means to control the state of said second and fourth switching means; sensor means responsive to first and second predetermined conditions of said first source and having an output for controlling the state of said first bi-state actuator and thereby controlling the state of said second bi-state actuator; said predetermined conditions causing said actuators to sequentially change state; said second actuator always completing its state change a predetermined period following the start of the state change of said first actuator when connecting either said first source or said second source to said load; said predetermined period being of sufficient magnitude such that one of said sources is electically disconnected from said load before the other one is electrically connected to said load; whereby during switching no interpower currents are produced.