Protection circuit for multiple phase power systems

A protection circuit for use with circuit breaker means for electrical apparatus operated by multiple phase, alternating current power systems characterized by a plurality of electrical distribution lines for transmitting electrical energy, the electrical energy in said lines having a spaced phase relationship, wherein said protection circuit comprises:

• first sensing means coupled to said lines for initiating a first signal responsive to detecting an undesirable phase imbalance between two or more of said lines, and detecting a low voltage on one or more of said lines;
• second sensing means coupled to said lines for detecting a phase reversal between two or more of said lines, said second sensing means initiating a second signal responsive thereto;
• circuit breaker operating means coupled to said second sensing means for operating said circuit breaker means responsive to said second signal;
• time delay means operably coupled between said first sensing means and said circuit breaker operating means, said time delay means for initiating said second signal to said circuit breaker operating means responsive to said first signal being received for a predetermined period of time;
• over-voltage protecting means coupled to at least one of said lines for detecting an over-voltage thereon and initiating said second signal responsive thereto, said second signal being coupled to said circuit breaker operating means for activation thereof;
• and
• power selector means coupled to at least two of said lines for supplying an output of AC power from a priority one of said lines to said circuit breaker operating means, said power selector means selecting said another one of said lines responsive to a loss of AC power on said priority line.