How does change in frequency affect the operation of a given transformer? with a decrease in frequency. A 60-Hz transformer will have when a 25-H

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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How does change in frequency affect the operation of a given transformer?
Ans. 1. Iron loss........ increases with a decrease in frequency. A 60-Hz transformer will have nearly
11% higher losses when worked on 50Hz instead of 60 Hz. However, when a 25-Hz trans-
former is worked on 60 Hz, iron losses are reduced by 25%.
2. Cu loss..........in distribution transformers, it is independent of frequecy.
3. Efficiency...........since Cu loss is unaffected by change in frequency, a given transformer effi-
ciency is less at a lower frequency than at a higher one.
4.
Regulation........regulation at unity power factor is not affected because IR drop is independent
of frequency. Since reactive drop is affected, regulation at low power factors decreases with
a decrease in frequency and vice-versa. For example, the regulation of a 25-Hz transformer
when operated at 50-Hz and low power factor is much poorer.
5. Heating..........since total loss is greater at a lower frequency, the temperature is increased with
decrease in frequency.
111
Transcribed Image Text:How does change in frequency affect the operation of a given transformer? Ans. 1. Iron loss........ increases with a decrease in frequency. A 60-Hz transformer will have nearly 11% higher losses when worked on 50Hz instead of 60 Hz. However, when a 25-Hz trans- former is worked on 60 Hz, iron losses are reduced by 25%. 2. Cu loss..........in distribution transformers, it is independent of frequecy. 3. Efficiency...........since Cu loss is unaffected by change in frequency, a given transformer effi- ciency is less at a lower frequency than at a higher one. 4. Regulation........regulation at unity power factor is not affected because IR drop is independent of frequency. Since reactive drop is affected, regulation at low power factors decreases with a decrease in frequency and vice-versa. For example, the regulation of a 25-Hz transformer when operated at 50-Hz and low power factor is much poorer. 5. Heating..........since total loss is greater at a lower frequency, the temperature is increased with decrease in frequency. 111
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