TPN MCCBs 1

[NickParker]

What is meant by TPN MCCB? Does the neutral terminal comes along with the MCCB? In a project where a contract SLD shows a TPN MCCB and my senior says we can provide 3 Pole MCCB and neutral shall be taken from the neutral bus. Now the question is If have a load which requires 3 phase 4 wire, the fourth wire (Neutral) being used just for the control transformer inside that load (Package load), Is it acceptable to provide 3 pole MCCB or do we have to provide TPN MCCB?

 

[ppedUK]

TPN MCCB is slightly incorrect terminology, but I would read this as 4 pole MCCB. If you require a ground fault module on the MCCB, then you will need a 4 pole MCCB. The same applies if you have an outgoing feeder with a reduced neutral and you need Neutral O/C protection.

 

[PA28]

Properly designed packaged type equipment generally do not need the neutral. The control voltage is derived inside with a control transformer with line to line input. This less troublesome than using neutral.

 

[RRaghunath]

TPN terminology was common with SFUs. TPN means the neutral contact closes first (before phase contacts) during closing operation and the neutral contact opens last (after phase contacts open) during opening operation.
This is to ensure that neutral connection is always available when the equipment is powered on, for safety reasons.

Rompicherla Raghunath