m = K_0 = \frac{N_1}{N_2} = \frac{300}{50} = 6

 \text{dato che } K_0 = \frac{V_1}{V_2} \ \Rightarrow\ 6 = \frac{380}{V_2}

 V_2 = \frac{380}{6} = 63{,}3\ \mathrm{V} \quad (\text{concatenata})

 \text{poi, dato che}\quad P = 3 E_2 I_2 \cos\varphi = 3\,\frac{V_2}{\sqrt{3}}\, I_2 \cos\varphi

 P = \sqrt{3}\, V_2 I_2 \cos\varphi \ \Rightarrow\ I_2 = \frac{P}{\sqrt{3}\, V_2 \cos\varphi} = \frac{5000}{\sqrt{3}\cdot 63{,}3 \cdot 0{,}8} \approx 57\ \mathrm{A}