Abstract:

Whether the critical current can be reliably broken is an important performance index of low voltage circuit breakers. The 2P DC 2000 V air circuit breaker can’t pass the experiment because the arc burning time is more than 1 s under the critical current of 64 A. Experimental analysis is carried out on various factors influencing the critical current test. The results show that the gas-generating material PA has the best gas-generating effect and a good deionization effect. Increasing the contact gap between the moving and stationary contacts from 45 mm to 60 mm can elongate the arc, effectively breaking low current DC arcs and increasing arc voltage. When the width of the narrow gap is changed to 10 mm, the product can pass the critical current test. Subsequent the refinements based on these findings ensure compliance with other performance requirements.

Key words: circuit breaker, critical current, arc ignition time, large contact gap, narrow gap gas generation