A 1000-VA, 230/115-V transformer has been tested to determine its equivalent cir-cuit. The results of the tests are shown below.Open-circuit test(on secondary side)Short-circuit test(on primary side)Vsc = 17.1 VYoc=115 VToc = 0.11 APoc 3.9 WPsc = 38.1 WIsc = 8.7 A4ChieSandry(a) Find the equivalent circuit of this transformer referred to the low-voltage side ofthe transformer. Seday(b) Find the transformer's voltage regulation at rated conditions and 45 0.8 PF lag-ging, (2) (3) Pending.(c) Determine the transformer's efficiency at rated conditions and 0.8 PF lagging.

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Answered: A 1000-VA, 230/115-V transformer has…

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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Similar questions

Consider an ideal transformer with N1=3000andN2=1000 turns. Let winding 1 be connected to a source whose voltage is e1(t)=100(1| t |)volts for 1t1ande1(t)=0 for | t |1 second. A2- farad capacitor is connected across winding 2. Sketch e1(t),e2(t),i1(t),andi2(t) versus time t.
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
dc tansformd
The windings of an 11500/2300V two winding transformer are connected in series, with 11500 V as the supply to the primary, to create an autotransformer. What is the voltage output of the resulting step-up autotransformer when Ip and Is are 10 A and 50 A, respectively?
A 250/125 V, five kVA single-phase transformer has a primary resistance of 0.2 ohms and reactance of 0.75 ohms. The secondary resistance is 0.05 ohm and reactance of 0.2 ohms.a) Determine its regulation while supplying full load on 0.8 leading p.f.b) The secondary terminal voltage on full load and 0.8 leading p.f.Ans.: -0.4.88%; 131.1
11- The output current corresponding to maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to sccondary of 0.25 2 is .. ampere. a- 20 b-25 c- 5 d- 400
Which of the following statements is true about an ideal transformer? O It changes the magnitude of DC signals. O It converts DC signals into AC signals. O It changes the magnitude of AC signals. O It converts AC signals into DC signals.
In a transformer that has 10 times more turns on the secondary side (side 2) than on the primary side (side 1), the magnitude of the voltage/EMF across the windings on the secondary side, E₂ will be... O a.... 10 times lower than the voltage/emf on the primary side, E₁. O b.... the same as the voltage/emf on the primary side. O c.... always zero regardless of the voltage on the primary side, E₁. O d.... 10 times higher than the voltage/emf on the primary side, E₁.
A transformer has primary and secondary turns of 1250 and 125 respectively. It has core cross-sectionof 36 cm2 and its rms flux density is to be limited to 1.4 T (to prevent core saturation). Whatmaximum 50 Hz voltage can be applied on the primary side and the corresponding open-circuitsecondary voltage?The core has a mean length of 150 cm and its relative permeability can be assumed to be 8000. Whatwould be the rms exciting current when the transformer’s primary winding is excited at a voltage ascalculated above? Also calculate the magnetizing susceptance as seen from primary and secondarysides.If the transformer were to be excited at 60 Hz, 1. What should be the maximum primary voltage for thecore flux density limit not to be exceeded? 2. What would be the magnetizing susceptance as seen oneach side in this case?
What conclusions we come up with after doing open circuit test on single phase transformer.
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…
3. A 3200/400 single-phase transformer has winding resistance and reactance of 30 and 132 respectively in the primary and 0.0292 and 0.0652 in the secondary. Express these in terms of (a) primary alone, (b) secondary alone. (ans. (a) 4.282, 17.16; (b) 0.067, 0.268)

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