ACB and MCCB both are used for safe making and breaking of electrical systems. In principle, both serve the same purpose.
ACBs are usually seen on upstream side of circuit & MCCBs on load side control (usually, load side switching operations are more frequent than upstream). Depending upon the
operating voltages and level of protection(Fault Level) needed for the system ,these three protection device are selected. As the technology has improved over the
period of time, the rating & breaking capacities of MCCBs are increasing - hence there is possibility of overlap in application of ACB & MCCB.