ICCB = Insulated Case Circuit Breaker. It's an older term for a cross between the lower cost testing and rating requirements of MCCBs (Molded Case Circuit Breakers) and the higher interrupting capacities associated with Air Circuit Breakers (aka Power Circuit Breakers), without the other expensive testing and design aspects of PCBs in terms of the longer hold-in times and such. Another way we used to like to think of them was PCBs with the UL listings of MCCBs, which allowed the removal of some of the bracing. The concept goes back to when MCCB design was good to about 50kAIC but if you needed 2000A, the transformer giving that to you might allow higher fault currents. So if you wanted a circuit breaker with more than that, you couldn't get it in an MCCB, but ACBs/PCBs were built to go into a different class of switchgear. So the breaker mfrs removed some of the unnecessary design elements for PCBs but used the same basic frame, calling them ICCBs. It's a somewhat archaic term any more, because the construction of MCCBs at high current levels has improved to the point where ICCBs being a different version became unnecessary. Some mfrs have eliminated them in their product lineups now as a result.
