Question

A 4-pole, 50Hz alternator has double layer winding with 10 turns per coil and number of slots are 60. If each coil is short pitched by an angle of ${36}^{\circ }$ electrical. The fundamental flux per pole is 0.015 Wb. The line to line induced emf for a 3-phase star connection is approximately

• A. 1050.2V
• B. 350.14 V
• C. 606.33V
• D. 1818.9V

Answer 1

The correct option is A 1050.2V

For double layer winding,
No. of slots = No. of coils

Total number of turns = $60\times 10=600$

Turns per phase = $\frac{600}{3}=200$

Pitch factor $\left(K_c\right)=\cos {18}^0=0.951$

Distribution factor $\left(K_d\right)=\frac{\sin \frac{m\beta }{2}}{m\sin \frac{\beta }{2}}$
$m=\frac{60}{4}\times \frac{1}{3}=5$

$\beta =\frac{180}{60/4}={12}^0$

$K_d=\frac{\sin \frac{5\times 12}{2}}{5\sin \frac{12}{2}}=0.9567$

$E_{ph}=\sqrt{2\pi }{K}_{\omega }\varphi f{T}_{ph}$

$E_{ph}=\sqrt{2\pi }\times 0.9567\times 0.951\times 0.015\times 50\times 200$

$E_{ph}=606.33V$

$E_{L-L}=\sqrt{3}\times 606.33V$

$E_{L-L}=1.05kV$