1、7D2ObjectThe object of this appendix is to state:-the general requirements for the co-ordination of a circuit-breaker with its associated fuse or fuses;-the methods and the tests intended to verify that the conditions for co-ordination have been met.D3 General requirements for co-ordination of a cir
2、cuit-breaker with its associated fuse or fusesD3.1 Take-over current The take-over current In(see Clause 9.5.1)shall be not greater than the breaking capacity of the circuit-breakeralone.D3.2 Behaviour of the circuit-breaker in association with its fusesFor all values of over-current up to and inclu
3、ding the breaking capacity assigned to the combination:a)The making operation of the circuit-breaker as well as the breaking operation of the combination shall notgive rise to external manifestations(such as emission of flames)projected beyond the limits stated by the manu-facturer(see Clause 9.2.2
4、a).b)There shall be no flashover between poles or between poles and frame,nor welding of contacts(seeClause 9.2.2 b).Note.-See also Clauses D5.2 and D5.3.D4 Type and characteristics of the associated fusesOn request,the manufacturer of the circuit-breaker shall state,in accordance with the relevant
5、IEC publications(Publications 269-1 and 269-2 or 269-3),the type and the characteristics of the fuses to be used with the circuit-breaker,and the maximum prospective short-circuit current for which the combination is suitable at the statedrated operational voltage.Whenever possible,the fuses shall b
6、e located on the supply side of the circuit-breaker.If the fuses are locatedon the load side,it is essential that the connections between the circuit-breaker and the fuses be so designed as tominimize any risk of short-circuit.D5 Methods for verification of the co-ordinationD5.1 Determination of the
7、 take-over currentCompliance with the requirements of Clause D3.1 shall be verified by comparing the characteristics of thecircuit-breaker and of the fuse.If the circuit-breaker is fitted with adjustable over-current opening releases,thevalue of break-time to be used shall be that at the minimum current setting.If the circuit-breaker may be fitted withinstantaneous over-current opening releases,the value of break-time to be used shall be that corresponding to thecircuit-breaker fitted with such releases.
