Bob,
The point I am trying to make is not about the requirements of the NEC that the branch OCPD be used to protect certain pieces of equipmentand appliances, which it clearly does.
My point is dealing strictly with the design and testing of branch OCPDs. Their primary purpose is to protect conductors. Their thermal curve is designed to be below the thermal damage curve of a properly rated conductor. Their instantaneous region is tested to protect the conductor from the forces of a short circuit. These design criteria are why it is difficult (and why the NEC includes special allowances) to chose a standard thermal magnetic breaker that will coordinate with motor and transformer inrush currents. A properly operating listed branch OCPD will protect a properly rated and installed conductor during a low impedance short circuit fault.
