A single-phase, two-winding transformer is rated 20 kVA, 480/120 volts, 60 Hz. The transformer equivalent resistance and reactance referred to the high voltage side are 0.1728 and 0.84 ohms, respectively. The transformer core loss at rated voltage is 200 W. When the transformer is loaded by half the rated load at 0.8 pf lagging and rated load voltage, the copper losses was found to be 75 W. a) Draw the transformer equivalent circuit referred to the HV side and draw its phasor diagram for the given load condition. b) Determine the transformer voltage regulation and efficiency at half load and 0.8 pf lagging. c) Determine the necessary load to be added in parallel to the original load (given above) to obtain maximum efficiency while making the system power factor equals to 0.9 lagging.

A single-phase, two-winding transformer is rated 20 kVA, 480/120 volts, 60 Hz. The transformer equivalent resistance and reactance referred to the high voltage side are 0.1728 and 0.84 ohms, respectively. The transformer core loss at rated voltage is 200 W. When the transformer is loaded by half the rated load at 0.8 pf lagging and rated load voltage, the copper losses was found to be 75 W. a) Draw the transformer equivalent circuit referred to the HV side and draw its phasor diagram for the given load condition. b) Determine the transformer voltage regulation and efficiency at half load and 0.8 pf lagging. c) Determine the necessary load to be added in parallel to the original load (given above) to obtain maximum efficiency while making the system power factor equals to 0.9 lagging.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.14P: A single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down...

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