Question:

A 7.2kVA single phase 50Hz, 480Vrms: 240Vrms transformer can be modelled using the primary referred approximate equivalent circuit shown in Figure 1 below.

Figure 1

Characterisation tests on the transformer have determined the circuit parameters for this transformer as:

R_eq = 0.84 Ω, X_eq = 1.6 Ω, X_o = 360 Ω, R_o = 800 Ω.

a)  Calculate the primary current and real power measurements that would result when an open circuit test is carried out on this transformer at rated primary voltage.

b)  Calculate the primary voltage and real power measurements that would result when a short circuit test is carried out on this transformer at rated primary current.

c)  Calculate the transformer secondary voltage for rated secondary current at a lagging power factor of 0.95, when the transformer is supplied at rated primary volts.