@ All (2) 18:04 May 9, 2020
So the ideal is that each terminal circuit should be protected by a device that sails as close to the wind as possible in respect of the rated current it needs to supply, while avoiding spurious tripping on momentary transient overload, such as motor starting currents, etc. But if each stage of the tree structure has to be protected by a device capable of carrying the sum of all the downstream devices (as would seem logical), going back up the line, you'd need some wildly over-rated supplies, cabling, etc.! But of course, not all devices are on all the time and/or always drawing their maximum current; hence ratings can be reduced to more practical levels; but all this requires terribly careful management of the trip settings and methods of controlling the overload / delay characteristic — which the devices being patented here are seemingly intended to facilitate. |