Based on the number of poles, the breakers are classified as-
SP – Single Pole
SPN – Single Pole and Neutral
DP – Double pole
TP – Triple Pole
TPN – Triple Pole and Neutral
4P – Four Pole
SP (Single Pole) MCB: In Single Pole MCCB, switching & protection is affected in only one phase.
Application: Single Phase Supply to break the Phase only.
DP (Double Pole) MCB: In Two Pole MCCB, switching & protection is affected in phases and the neutral.
Application: Single Phase Supply to break the Phase and Neutral.
TP (Triple Pole) MCB: In Three Pole MCB, switching & protection is affected in only three phases and the neutral is not part of the MCB.
3 pole MCCB signifies for the connection of three wires for three phase system (R-Y-B Phase).
Application: Three Phase Supply only (Without Neutral).
TPN (3P+N) MCB: In TPN MCB, Neutral is part of the MCB as a separate pole but without any protective given in the neutral pole (i.e.) neutral is only switched but has no protective element incorporated. TPN for Y (or star) the connection between ground and neutral is in many countries not allowed. Therefore the N is also switches.
Application: Three Phase Supply with Neutral.
4 Pole MCB: 4pole MCCB for 4 wires connections, the one additional 4th pole for neutral wire connection so that between neutral and any of the other three will supply.
In 4-Pole MCCBs the neutral pole is also having protective release as in the phase poles.
Application: Three Phase Supply with Neutral.