1.1 Scope of application added at the end of the first paragraph: This section specifies supplementary technical requirements applicable to single pole and two-pole circuit breakers operating in DC circuits. The rated DC voltage of a single pole circuit breaker shall not exceed 220 V, the second pole shall not exceed 440 V, the rated current shall not exceed 125A, and the rated DC short-circuit capacity shall not exceed 10000 A. Note: This section is applicable to circuit breakers that can connect and disconnect AC current as well as direct O current. The last two paragraphs are deleted. 1.2 Purpose Delete item 6. Chapter 2 of the normative reference document GB 10963-1999 applies, but with the following modifications: delete GB 16917.1-1997, GB 16917.21-1997, GB 16917.22-1997
3 Terminology and Definitions GB10963-1999 Chapter 3 is applicable, but with the following modifications: Add a new definition: 3.5.20 Time constant The time T-L/R (ms) when the expected DC current rises to 0.63 times the maximum peak current
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