Medium-Capacity Air-Blast Circuit Breakers for Metal-Clad Switchgear

The cross-blast principle of arc interruption has been shown to provide maximum air economy; consequently this method of interruption is well suited for use in an air-blast breaker that must conform to the rigid space requirements and small phase spacings encountered in medium- capacity metal-clad equipment. It is shown that proper co-ordination of the operating mechanism, air supply, interrupting chamber, and resistor make possible a design to meet these requirements. The principle of operation is discussed and it is shown how a resistance is utilized to provide further air economy.