When do we have to use a TP circuit breaker, and when do we have to use a TPN breaker, and why? I am specifically referring to 415 VAC 3 phase, 230 VAC in single phase, 50 HZ.
TPN for Y (or star) is a 4 pole breaker where Neutral is not sensed but switched with the 3 phases.
The connection between ground and neutral is in many countries not allowed. Therefore TPN is used and the N also switches for these locations.