Consider the solution of Example 11.4.1. By means of a phasor diagram, determine the load power factor for which the regulation is maximum (i.e., the poorest), and find the corresponding regulation.
Example 11.4.1
The transformer of Example 11.3.1 is supplying full load (i.e., rated load of 50 kVA) at a rated secondary voltage of 240 V and 0.8 power factor lagging. Neglecting the exciting current of the transformer,
(a) Determine the percent voltage regulation of the transformer.
(b) Sketch the corresponding phasor diagram.
(c) If the transformer is used as a step-down transformer at the load end of a feeder whose impedance is 0.5 + j2.0 Ω, find the voltage VS and the power factor at the sending end of the feeder.
Example 11.3.1
Compute the efficiency of the transformer of Example 11.3.1 corresponding to (a) full load, 0.8 power factor lagging, and (b) one-half load, 0.6 power factor lagging, given that the input power Poc in the open-circuit conducted at rated voltage is 173 W and the input power Psc in the short-circuit test conducted at rated current is 650 W.