1.a. Separate voltage-regulating units provide voltage-ratio control under load by A. causing different impedance drops in each phase. B. combining voltages from different phases. C. having series transformers in phase with the line-to-neutral voltage. D. exciting transformers having their primaries delta-connected. 1.b. A reactor is sometimes used with an autotransformer to A. limit short-circuit current. B. increase the full-load current. C. provide increased internal impedance. D. decrease the voltage ratio.

1.a. Separate voltage-regulating units provide voltage-ratio control under load by A. causing different impedance drops in each phase. B. combining voltages from different phases. C. having series transformers in phase with the line-to-neutral voltage. D. exciting transformers having their primaries delta-connected. 1.b. A reactor is sometimes used with an autotransformer to A. limit short-circuit current. B. increase the full-load current. C. provide increased internal impedance. D. decrease the voltage ratio.

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 3.56P: Three single-phase two-winding transformers, each rated 3kVA,220/110volts,60Hz, with a 0.10 per-unit...

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1.a. For performing dielectric-strength tests on insulating materials, two transformers are connected in aA. parallel combination.B. cascade arrangement.C. polyphase arrangement. 1.b. In large power transformers, the unequal voltage distribution caused by voltage surges in the winding isprevented by the use ofA. static shields.B. series capacitors.c. low-voltage arresters.
1.b. In large power transformers, the unequal voltage distribution caused by voltage surges in the winding isprevented by the use ofA. static shields.B. series capacitors.c. low-voltage arresters.
Consider the three single-phase two-winding transformers shown in Figure. 3. The high-voltage windings are connected in Y. (a) For the low-voltage side, connect the windings in A, and label the terminals a, b, and c in accordance with the American standard. (b) Relabel the terminals a', b', and c' such that VAN is 90° out of phase with V₂'b' for positive sequence. DI H₂ Figure. 3: Three-Winding Transformer
9. In the design of current transformers, compensation for ratio errors is accomplished by using A. increased exciting current value. B. parallel secondary windings. C. low-permeability core material. D. extra turns on the primary.
12.a. Comparing the transformer cores of core-form and shell-form transformers shows that thea. shell form provides lower reactance without increasing the transformer size.b. core form makes possible wider coils and better oil circulation.c. shell form is used exclusively in small low-voltage transformers.12.b. Distribution transformers are generally protected from damage due to excessive internal temperatures,by the operation of aA. lightning arrester.B. circuit breaker.C. surge diverter.
a. Write a table consists of well- known power capacity of distribution transformers . b . Write a table consists of standard magnitudes of turn-ratios of current transformers . C.Discuss the above tables .
The core of a three phase, 50 Hz, 11000/550 V delta/star, 300 kVA, core-type transformer operates with a flux of 0.05 Wb. Find (i) number of H.V. and L.V. turns per phase. (ii) e.m.f. per turn (iii) full load H.V. and L.V. phase-currents.
A three-phase, 4-pole, 1,500 rpm alternating having a double layer-windings with 18 turns per coil. The slots per pole per phase are 10 and the coil span is 22 slots. The spread phase is 60 degrees and the flux per pole is 0.0625 Weber. If the armature windings are wye connected. a) Determine the generated voltage per phase and the line to line voltages. b) If the alternator is delivering a three - phase load of 1,200KW at 0.8 lagging power factor what is the line current of the alternator
A 50 Hz 1-phase transformer has a turn-ratio of 6. The resistances are 0.90 ohm and 0.03 ohm and the reactance’s 5 ohm and 0.13 Q for high voltage and low voltage respectively. Determine (a) the voltage to be applied to the high voltage side to obtain full load current of 200 A in the low voltage winding on short circuit (b) the p.f. on short circuit.
5. Write down the equations of a single phase transformer at no-load mode. Give the names of the resistances, reactance, e.m.f.'s, currents and voltages.
Find the elements of the equivalent circuit relative to the secondary of a single-phase transformer. The no-load voltages in the primary and secondary circuit are 200 and 400 volts, respectively, and at a frequency of 50 Hz. The primary no-load current at a voltage of 200 volts is 0.7 amps and the losses in the core are 70 watts. The resistance and reactance of the primary are 3.2 and 1.25 ohms, respectively. Secondary resistance and reactance 6.0, 0.07 ohms, respectively. Draw the equivalent circle, showing the values of its elements.
Find the elements of the equivalent circuit relative to the secondary of a single-phase transformer. The no- load voltages in the primary and secondary circuit are 200 and 400 volts, respectively, and at a frequency of 50 Hz. The primary no-load current at a voltage of 200 volts is 0.7 amps and the losses in the core are 70 watts. The resistance and reactance of the primary are 3.2 and 1.25 ohms, respectively. Secondary resistance and reactance 6. 0, 0.07 ohms, respectively. Draw the equivalent circle, showing the values of its elements.