Calculate Number of Turns Per Phase: Electrical Machines Exam

[ric115]

Hi there

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

 

[Valkarie]

.Yes, you can use the voltage ratio formula to calculate the number of turns in each winding. First, you need to calculate the total core area by subtracting the 10% insulation from the gross area (which is the area of the circumscribing circle). Then, use the formula N1/N2 = (V1/V2)^2 x B / 4.44fA, where N1 and N2 are the number of turns in the low-voltage and high-voltage windings respectively, V1 and V2 are the line voltages, B is the maximum flux density, f is the frequency of the transformer and A is the total core area.