Fundamentals of Energy Systems HW5 Q1 1. (a) What are different losses occurring in a transformer? (b) How do wemodel them in the transformer model? (c) What is the typical range of effi-ciency of a power system transformer?

a) There are two types of major losses in transformers. One is core losses, which are normally…

Answered: 1. (a) What are different losses…

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 3.28MCQ

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For a short-circuit test on a 2-winding transformer, with one winding shorted, can you apply the rated voltage on the other winding? (a) Yes (b) No
Why is it important to reduce the moisture within a transformer to acceptable levels during transformer installation?
In developing per-unit circuits of systems such as the one shown in Figure 3.10. when moving across a transformer, the voltage base is changed in proportion to the transformer voltage ratings. (a) True (b) False
An ideal transformer has no real or reactive power loss. (a) True (b) False
If we increase the load than core loss and copper loss will... Decrease Increase Remain same
The eddy current and hysteresis losses of a 4400-V, 60-Hz, 10 distribution transformer are 280 W and 560 W, respectively. Determine the core loss when the transformer is connected across a 4600-V, 50-Hz source. Your answer
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14. The output current corresponding to maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to secondary of 0.2: is .. ampere. (a)20 (b)25 (c)5 (d) 400 15. At relatively light loads, transformer efficiency is low because (a) secondary output is low (b) transformer losses are high (c) fixed loss is high in proportion to the output (d) Cu loss is small. 16. When a 400-Hz transformer is operated at 50HZ its kVA rating is (a) reduced to 1/8 (b) increased 8 times (c) unaffected (d) increased 64 times. 17. The voltage applied to the h.v. side of a transformer during short-circuit test i of its rated voltage. The core loss will be..percent of the rated core loss. (a)4 (b) 0.4 (c)0.25 (d)0.04 18. The main purpose of performing open-circuit test on a transformer is to meas its (a) Cu loss (b) core loss (c) total loss (d) both Cu and total losses. 19. During short-circuit test, the iron loss of a transformer is negligible because (a) the entire input…
P2-Draw the equivalent circuit of a single-phase transformer and explain how the core losses are almost invariant to the load (current). How do they depend on the terminal voltages of the transformer? Also, using the equivalent circuit explain how the copper losses depend on the load current.
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…
BListen Tron Joss in a transformer: Cais dependent on load current. b) is a function of the resistance of the primary and the secondary windings. Cis a function of eddy currents and hysteresis effects in the transformer core. d) ) can be reduced by ¼ by reducing the current by 2.

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1. (a) What are different losses occurring in a transformer? (b) How do we model them in the transformer model? (c) What is the typical range of effi- ciency of a power system transformer?