Difference Between a 3-POLES+N and 4POLES (CB 40A 400V) (Curve D) in 3PH+N Inst

A1) The neutral current does not/does trip the device, respectively. How one gets more than 40A in the neutral is the question you didn't ask.

A2) 40A in both cases.

A3) Where it says so on the wiring diagram for the equipment you're considering putting each of them in, Boss.

The answer can be found in one of my previous comment here.

For convenient it is pasted again:

Type of breakers based on number of pole:

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

The difference between TPN and 4P (or SPN and DP):

For TPN, protection applies to the current flow through only 3 poles; there is no protection for the current flow through the neutral pole. For the 4 pole breakers, protection applies to current flow through all poles. However when breaker trips or manually opened, all poles are disconnected.

Same type of difference also applies for SPN and DP.

Usage of TP, TPN and 4P in distribution panel:

For any distribution board, the protection system (either fuse and switch or breaker) must be used in the incomer. For a three phase distribution panel, either TP or TPN or 4P can be used as the incoming protection.

TP: It is most commonly used type in all ordinary cases.

TPN: It is generally used where there are dual sources of incomer to the panel (utility source and emergency generator source).

4P: It is used where is the possibility of high neutral current (due to unbalance loads and /or 3^rd and multiple of 3^rd harmonics current etc).

- MS