# Calculate inductance for 3-phase double ckt line    I have attached the problem with the solution given in my workbook. I attempted the problem and ended up getting a different answer.

Is my solution wrong ?

Please help me to understand the problem.

## 1 Answer

It's mainly due to rounding errors in the written example. For instance, it calculates a value as being 0.243 but if you do the math yourself it is 0.2437. When they calculate 0.221, it would be more accurate to use 0.2214. When they calculate 0.235 based on those previous values it is closer to 0.236. When you follow it all through you get a value of 0.61345 i.e. very close to what you got.

Beware of rounding errors.

• But the method for calculating Dm is different in my solution and what is given in the workbook. Why both method works? – Nikhil Kashyap Feb 25 '18 at 20:30
• Sir, why both methods give the same result that is my doubt ? – Nikhil Kashyap Feb 26 '18 at 17:56
• I suspect that mathematically they are equivalent but look different when viewed somewhat casually. – Andy aka Feb 26 '18 at 18:11