How do you calculate the tollerances from a 3 phase winding measurement

[k1gabi]

Assuming that you measure the windings for a power transformer, for example:
A-B: 2,258 ohms
B-C: 2,262 ohms
A-C: 2,250 ohms, how do you calculate the tolerances for these? What formula do you use? You consider as reference the highest or the lowest value from every 2 readings?
I just wanna check an industry tollerance of +/- 5%.
Thanks.

 

[marconi]

Are these dc resistance measurements?

Assuming for now they are then:

1. Find the mean average of the resistances of the three windings. Thus Rmean = (2258 + 2262 + 2250) / 3;

2. Find the percentage difference D of each winding resistance from Rmean. Thus for example for the first winding

D1 = (2258 - Rmean) x 100 / Rmean

3. Now compare D1, D2 and D3 to +/- 5%