Exercises
1. A 25 kVA single-phase transformer has the primary andsecondary number of turns of 200 and 400, respectively. Thetransformer is connected to a 220 V, 50 Hz source. Calculate the(i) turns ratio, and (ii) mutual flux in the core.
2. A 25 kVA, 2200/220 V, 50 Hz single-phase transformer’s lowvoltage side is short-circuited and the test data recorded from thehigh voltage side are P=150 W, I1 = 5A and V1 = 40 V. Determine the(i) equivalent resistance, reactance and impedance referred toprimary, (ii) equivalent resistance, reactance and impedancereferred to secondary.
3. A 30 kVA transformer has the iron loss and full load copperloss of 350 and 650 W, respectively. Determine the (i) full loadefficiency, (ii) output kVA corresponding to maximum efficiency,and (iii) maximum efficiency. Consider that the power factor of theload is 0.6 lagging. (97.74%, 13.2 kW, 94.96%).
4. A 2.5 kVA, 200 V/40 V single-phase transformer has theprimary resistance and reactance of 3 and 12 Ω, respectively. Onthe secondary side, these values are 0.3 and 0.1 Ω, respectively.Find the equivalent impedance referred to the primary and thesecondary. (17.9ohms, 0.72ohms).
