Vacuum type electric circuit breaker

Claim 1

A high voltage electric circuit breaker which is rated to interrupt fault currents of tens of thousands amperes and to interrupt capacitance currents of hundreds of amperes, comprising: a. a main circuit interrupter of the vacuum-type comprising a pair of separable contacts and a highly evacuated insulating housing enclosing said contacts, b. main operating means for separating said contacts to draw a fault current arc therebetween during a fault-current interrupting operation, c. a resistor connected in parallel with said contacts for reducing the severity of the recovery voltage transient developed across said contacts when they are separated during a fault-current interrupting operation, d. auxiliary interrupting means having separable contacts connected in series with the parallel combination of said vacuum interrupter contacts and said resistor, e. said auxiliary interrupting means having sufficient capacitance-current interrupting ability upon separation of its contacts to interrupt without assistance from said vacuum-type circuit interrupter the most severe capacitance currents for which said circuit breaker is rated, f. auxiliary operating means operable in response to initiation of the operation of said main operating means for opening said auxiliary interrupting means to separate its contacts a few half-cycles after said main interrupter''s contacts are separated during a fault-current interrupting operation, g. and means operable during a capacitance-current interrupting operation for causing said auxiliary operating means to separate the contacts of said auxiliary interrupting means while said vacuum interrupter contacts are still closed or simultaneously with separation of said vacuum interrupter contacts, whereby said auxiliary interrupting means assumes the capacitance-current interrupting duty and relieves said vacuum interrupter therefrom.