Want to ask PC level double power supply front-end circuit breaker with thermal magnetic protection, what is the reason?
Article 4.1.2 of the code for the design of low voltage distribution, GB50054-95 stipulates that "the protection of electrical equipment in the upper and lower levels adopted in the distribution line shall be selective, and coordination shall be coordinated among all levels.". But for non important load protection appliances, non selective cutting can be used." According to the above requirements, using dual power supply distribution system, when the double power supply terminal automatic mutual throwing distribution box, cabinet with multiplex a load or load two outgoing line circuit, the automatic transfer switch is arranged in front of the fuse or isolation type low voltage circuit breaker shall be with the electrical distribution box, cabinet outlet selective coordination between circuit of low-voltage circuit breaker.
Short circuit protective equipment in accordance with isolation requirements:1. fuse2. fuse type switch3. fuse type isolator4. isolated low voltage circuit breaker in line with IEC947-3 isolation standard requirements.
Due to the following factors, short-circuit protection devices shall be installed at the front end of the PC level automatic switch equipment in the distribution box and cabinet:(1) although the PC level automatic change-over switch has the ability to withstand short circuit current, but it has no ability to cut short circuit current, it needs to set up short-circuit protector at the front end.(2) in addition, the requirement of isolating electrical equipment should be considered.
PC level automatic change-over switch has power conversion function, no short circuit and overload protection function. The rated current is less than or equal to PC 250A automatic switch electrical appliance, rated short-time withstand current effective value (1) in general about 5KA-12KA; rated current is greater than 250A and less than or equal to PC 630A automatic switch electrical appliance, rated short-time withstand current effective value (1) in general about 13KA-25KA.
