MCB come in Type Numbers or Letters 1 to 3 or B to D and these refer to the magnetic part of the trip and how many times the thermal rating it will instant trip at Type1= 4x, Type2= 7x, Type3= 10x, TypeB= 5x, TypeC= 10x, TypeD= 20x if you take voltage and divide by this number you come up with a number that when divided in turn by the current will give max Zs for example for a type B MCB at 230 volt we get 46 as number to divide by the amps so a 16 amp B type MCB will be 2.875ohms using same example with 240 volt will give 3ohms since you don’t give type letter or number on MCB can’t give you values only how to work it out.
6 For B Type 7.666666667 Ω For C Type 3.833333333 Ω For D Type 1.916666667 Ω
16 For B Type 2.875 Ω For C Type 1.4375 Ω For D Type 0.71875 Ω
32 For B Type 1.4375 Ω For C Type 0.71875 Ω For D Type 0.359375 Ω
40 For B Type 1.15 Ω For C Type 0.575 Ω For D Type 0.2875 Ω
This at 230 volt as 17th Edition the old 16th was at 240 volt all values calculated so slightly different to book values as not corrected to 3 significant figures.
Does help Eric