2. Table 1 gives the types and size of various loads that will be connected to a three-phase transformer. DEVICES Lamps 1 HP, 1ф Motor 10 HP, 30 Motor b) QUANTITY 20 10 5 VOLTS 120 120 240 AMPS/UNIT 1 9.8 3.5 Table 1 Determine the KVA capacity of the three-phase transformer required. Draw the connection the transformer connection and show how each load must be connected

2. Table 1 gives the types and size of various loads that will be connected to a three-phase transformer. DEVICES Lamps 1 HP, 1ф Motor 10 HP, 30 Motor b) QUANTITY 20 10 5 VOLTS 120 120 240 AMPS/UNIT 1 9.8 3.5 Table 1 Determine the KVA capacity of the three-phase transformer required. Draw the connection the transformer connection and show how each load must be connected

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 3.57P: A two-winding single-phase transformer rated 60kVA,240/1200V,60Hz, has an efficiency of 0.96 when...

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A two-winding single-phase transformer rated 60kVA,240/1200V,60Hz, has an efficiency of 0.96 when operated at rated load, 0.8 power factor lagging. This transformer is to be utilized as a 1440/1200-V step-down autotransformer in a power distribution system. (a) Find the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the ratings as a two-winding transformer. Assume an ideal transformer. (b) Determine the efficiency of the autotransformer with the kVA loading of part (a) and 0.8 power factor leading.
An infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.
The nameplate on a transformer will indicate whether or not it is a Class 2 transformer. (True) (False) (Circle the correct answer.)
An open-delta three-phase transformer system has one transformer center-tapped to provide a neutral for single-phase voltages. If the voltage from line to center tap is 277 V, what is the high-leg voltage?
A single-phase l0-kVA,2300/230-volt,60-Hz two-winding distribution transformer is connected as an autotransformer to step up the voltage from 2300 to 2530 volts (a) Draw a schematic diagram of this arrangement, showing all voltages and currents when delivering full load at rated voltage. (b) Find the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the rated values as a two-winding transformer. How much of this kVA rating is transformed by magnetic induction? (C) The following data are obtained from tests carried out on the transformer when it is connected as a two-winding transformer: Open-circuit test with the low-voltage terminals excited: Applied voltage =230V, input current =0.45A, input power =70W. Short-circuit test with the high-voltage terminals excited: Applied voltage =120, input current =4.5A, input power =240W. Based on the data, compute the efficiency of the autotransformer corresponding to full load, rated voltage, and 0.8 power factor lagging. Comment on why the efficiency is higher as an autotransformer than as a two-winding transformer.
Rework Problem 3.14 if the transformer is delivering rated load at rated secondary voltage and at (a) unity power factor, (b) 0.8 power factor leading. Compare the results with those of Problem 3.14. -
17. A transformer rated 300 kva with the high-voltage winding designed for 2300 volts will most probablybe aA. power transformer with shell-form core.b. distribution transformer with cylindrical coils.c. distribution transformer with disk coils.
Solve the following problems with complete solutions and units usingtwo(2) decimal digits. 1. A 25-kVA, 1-phase transformer, 2,200 volts to 220 volts, has a primaryresistance of 1.0 Ω and a secondary resistance of 0.01 Ω. Find theequivalent secondary resistance and the full-load efficiency at 0.8power factor if the iron loss of the transformer is 80% of the full-loadcopper loss.
A three phase transformer is used for ancillary services in a thermal power plant. It shows the following nameplate data: 30 MVA, 20/6.6 kV, and an impedance of 8%. The transformer has 21 taps to change the tap ratio in 1% increments. Neglect the transformer resistance. a) If the voltage at the high side is 18.5 kV, determine the tap ratio that must be used under a full load condition at unity power factor. b) What is the number of the actual tap? Assume you start counting from the lowest possible tap.
19.A 25kVA, 2400/240, 60Hz single phase transformer gave the following short circuit test result Vsc = 100V, Isc = 10.41A, Psc = 116. Find the equivalent resistance in ohms referred to primary. Assume Ip rated is equal to Isc. round off answer to 4 decimal places if necessary.
3 phase, delta / delta , 50 Hz , 300 KVA , 2400 : 600 V transformer feedana basanced full load whose laggong power factor is 0,7 at nominal voltage. a) calculate the iron losses of the transformer? b)calculate the copper losses of the transformer? c) efficiency of the transformer?
Calculate the number of turns needed in the secondary winding of a transformer to transform a primary voltage of 300 volts down to a secondary voltage of 180 volts, if the primary winding has 1150 turns of wire. ANS. Nsecondary= 690 turns