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External CT with Masterpact M & NW exchange retrofitting

Replcement of Masterpact M to Masterpact NW using retrofitting kits. Upon inspection of the unit to be replaced it showed it have an external CT at the neutral and wired to T1 and T2 terminal of Masterpact then connected to its STR trip units. our question is, in case there our client ask us the difference between the two. 1. Thus Terminal T1 and T2 is the same in Masterpact NW? 2. How it is connected? Can we use the same terminal in Masterpact NW? 3. How about T3 and T4 in NW? how it is wired? 4. What is the function of terminal T3 and T4?

The Masterpact M and the NW don't use the same external CT so you must replace Fixes also the external CT in association with the Masterpact M. Why the external CT has T3 and T4 when the external CT has onlt T1 and T2 ? Because the technology of the external CT for the NW is different T1 and T2 connections concern the iron CT to provide power supply to the trip unit and the T3 and T4 connection concern the air CT for the measurement (Rogwosky type). The wiring of the external CT is given in the Masterpact catalog and T1 and T2 must be removed if the external sensor is used, you have also the wiring concerning of residual earth fault protection.
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