ABB- VD4 Circuit Breaker - Closing Circuit Explanation

It is very difficult to understand the electrical circuit without an understanding of the mechanism that the electromagnetic components operate.

Generally, the closing mechanism will store enough mechanical energy to also rapidly open the contactor with a very low current. This helps ensure that if you close the circuit, you will be able to open it under the worst possible conditions, ie a 3 phase bolted short circuit where the line to line voltage is essentially zero.

So the closing circuit will normally consume a relatively large amount of energy, to close the mechanism, and the energy required to eventually rapidly open the current carrying contacts. Being a vacuum contactor, magnetic blowout coils and arc cooling chutes are not needed.

So a pilot duty circuit such as 49, 10 and 20 is required so you don’t need #8 wires in your control panel.

The next part of the circuit handles the heavy current part, and also sets up a latch that requires a very low current, to release the trip springs, when it’s time to open the contacts.

Try this.