VCB/ACB AT Ratings 1

[tlp23]

Hi,

Like we mention AF/AT (Ampere Frame/Ampere Trip)ratings for MCCB, is there any thing that we can mention the same for ACB's & VCB's.
If so, for a 1200A frame VCB, what are the AT ratings available.

thaks in advance,
tlp23

 

[Kapai]

These are LV devices? ACB = Air circuit breaker and MCCB = moulded case circuit breakers have the AF/AT concept. I have only ever seen this AF/AT used in a limited number of countries (e.g. Singapore) and only on low voltage. So installing an 800 A trip unit in a 1200 A CB means that the circuit can never be set above 800A (unless the trip unit is replaced).

VCB is a vacuum circuit breaker? This is not LV technology in my experience and the AF/AT concept is invalid. It will normally have a same manufacturer's protection relay installed, but should support any manufacturer's relay as required. The tripping levels are as adjustable as the relay permits, but usually quite a wide range, and could also depend on CT selection.