Calculating Number of Turns for a 50Hz 3-Phase Transformer: A Step-by-Step Guide

[ric115]

Hi there

I am presently studying for my electrical machines exam and i have a few examples to tackle.

A 50hz, 3 phase, core-type transformer is connected star-delta and has a line voltage ratio of 11000/400V. The cross-section of the core is square with a circumscribing circle of 0.6m diameter

If the maximum flux density is about 1.2T, calculate the number of turns per phase on the low-voltage and on the high-voltage windings. Assume the insulation to occupy 10 per cent of the gross core area.


So i have;

V1= 11000
V2= 400
B = 1.2T
A = 0.6m (i think?)

Could i use the V1/V2 = T1/T2 formula here?

Anyhelp on this topic would be greatly appreciated :O) rather do my mistakes here than on the exam

 

[NateD]

!Yes, you can use the formula V1/V2 = T1/T2. To solve this problem, you need to know the area of the core. Since the core is square, its area is equal to (0.6m)2 = 0.36m2. Now the effective area of the core is the gross area minus the insulation area, so we can calculate the effective area as follows: Aeff = (1 - 0.1) x 0.36m2 = 0.324m2 Now we can use the formula F = BAeff to calculate the flux, where F is the flux and B is the maximum flux density: F = 1.2T x 0.324m2 = 0.388Wb Now we can use the formula N1/N2 = (F1/F2) x (V2/V1) to calculate the number of turns per phase on both windings: N1/N2 = (400/11000) x (0.388/1) = 0.035 So the number of turns per phase on the low-voltage winding is: N1 = 0.035 x 11000 = 385 turns And the number of turns per phase on the high-voltage winding is: N2 = 0.035 x 400 = 14 turns