The primary winding of the welding transformer contains 120 turns of wire with a cross section of 20 mm2; its resistance is 8·10-2 Ohm. At rated load, the current is 40 A. How many turns does the secondary winding contain and what is the cross-section of its wire if the transformation ratio k = 220/60? Assuming that the windings are wound on the core in one layer, determine the resistance of the secondary winding. Neglecting losses due to magnetization reversal and Foucault currents (i.e. losses in steel), determine power losses due to heating of the windings and the efficiency of the transformer. The useful power of the transformer is 8 kW.

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