A) Calculate the efficiency of the test transformer at the followingloading conditions :(X=15%, 25%, 50%, 75%, 100% and 125% ofthe full load), for the following load types:i. Resistive load (Cos=1).ii. Inductive load (Coso=0.8 lagging).B) From part (A) draw in the same graph paper the plot of efficiency(Y-axis) vs output power (X-axis) of the transformer for both resistiveand inductive loads.Take the scale of X-axis,each 1 cm =100 W.Take the scale of Y-axis,each 1 cm =4%.C) Discuss the plots of part (B).

Step 1: The efficiency of the test transformers loaded with given loading conditions , load…

Answered: A) Calculate the efficiency of the test…

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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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
An ideal transformer has no real or reactive power loss. (a) True (b) False
For an ideal transformer, the efficiency is (a) 0 (b) 100 (c) 50
The symbol shown is a(n) a. iron core transformer. b. auto transformer. c. current transformer. d. air core transformer.
For the transformer in Problem 3.10. The open-circuit test with 11.5 kV applied results in a power input of 65 kW and a current of 30 A. Compute the values for GcandBm in siemens referred to the high-voltage winding. Compute the efficiency of the transformer for a load of 10 MW at 0.8 p.f. lagging at rated voltage.
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?
The core of a transformer operating at 50 Hz has an eddy current loss of 100 W/m3 and the corelaminations have a thickness of 0.50 mm. The core is redesigned so as to operate with the same eddycurrent loss but at a different voltage and at a frequency of 250 Hz. Assuming that at the new voltage themaximum flux density is one-third of its original value and the resistivity of the core remains unaltered,determine the necessary new thickness of the laminations. Clear and detailed solution.
helpp
The resistance and reactance of the primary winding of a 440/110 V single phase transformer are 4.4 ohm and 8 ohm respectively. The resistance and reactance of the secondary winding are 1.6 ohm and 2ohm respectively. Then find the equivalent resistance, reactance and impedance referred to the primary side.
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…

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