Description : Find the ratio of refractive index of medium 2 to that of medium 1, when the Brewster angle is 60 degree. a) 0.707 b) 1.5 c) 0.866 d) 1.732
Last Answer : d) 1.732
Last Answer : Turns ratio= N1/ N2 IN Scott connection Main transformer turns ratio = N1 /N2 Teaser transformer turns ratio= 0.866N1/N2 Where N1= number of turns in primary winding N2= number of turns in secondary winding
Description : The two watt meters measurement the ratio of two meter readings is –(1-sqrt3):( 1+sqrt3) then the power factor is a) 1 b) 0.866 c) 0.707 d) 0
Last Answer : Ans: 0.707
Description : A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (B) less than 4.5%. (C) more than 4.5%. (D) 4.5% or more than 4.5%.
Last Answer : (C) more than 4.5%.
Description : Explain with the neat circuit diagram only the scott connection scheme for conversion of three phase supply to two phase supply. Name one application of the same.
Last Answer : Three-phase to Two-phase Transformation (Scott Connection of Transformers): Working: i) Scott connection can be used for three-phase to two-phase conversion using two single-phase transformers ... a 3-phase system with a two-phase system with the flow of power in either direction.
Description : (a) Define permeability. (b) Define MMF. (c) Define form factor of an alternating quantity. (d) Define frequency and time period of an alternating quality. (e) Define transformation ratio of transformer. ... and state the meaning of each term used. (g) Give two applications of single phase motors.
Last Answer : Permeability : It is the ability of a magnetic/Non magnetic material to allow setting up of flux in it. MMF : The magneto motive force (MMF) is the force required to setup flux in a magnetic / ... applications of single phase motors : Water pumps, ceiling fan, lathe machine
Description : What is transformation ratio for step up, step down and isolation transformer?
Last Answer : K>1 for step up transformer K
Description : What is the transformation ratio in transformer?
Last Answer : Equation for transformation ratio is, E2/E1 = N2/N1 = k k = >1 in step up transformer, where secondary turns are more and thus voltage is more to reduce the transmission current. k =
Description : What will happen if transformer in parallel connection have different phase sequence ?
Last Answer : If the phase sequence is in an incorrect manner, in every cycle each pair of phases will get short-circuited.
Description : Coordinate of â- ABCD is WCS are: lowermost corner A(2,2) & diagonal corner are C(8,6). W.r.t MCS. The coordinates of origin of WCS system are (5,4). If the axes of WCS are at 600 in CCW w.r.t. the axes of MCS. Find new ... in MCS. a.(4.268, 6.732) b.(5.268, 6.732) c.(4.268, 4.732) d.(6.268, 4.732)
Last Answer : a.(4.268, 6.732)
Description : What is the supply rated o/p if two single phase transformer connect to give three phase o/p from a three phase I/p?
Last Answer : A. Each transformer is only capable of supplying 86.6%of its o/p rating
Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.
Last Answer : (A) Both eddy current and hysteresis losses decreases.
Description : What will happen if transformer in parallel connection have different percentage impedance or X/R ratio ?
Last Answer : A difference in the ratio of the reactance value to resistance value of the per unit impedance results in a different phase angle of the currents carried by the two paralleled transformers; one ... of the combined output. Hence, the real power will not be proportionally shared by the transformers.
Description : What will happen if transformer in parallel connection have different voltage ratio?
Last Answer : Two transformers in Parallel should have the same primary and secondary voltage ratings. Any error in the voltage ratio would cause heavy circulating currents to flow between the transformers. ... in overloading of one transformer. This circulating current will result in increased copper losses.
Description : Which of the listed transformer uses a single winding to produce voltage transformation? A. Stepup transformers B. Stepdown transformers C. Autotransformers D. Isolation transformers
Last Answer : Answer: C
Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus
Last Answer : Answer: B
Description : A simple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is (A) 86.7% (B) 88.26% (C) 88.9% (D) 87.8%
Last Answer : A simple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is 87.8%
Description : A single-phase, 50 kVA, 250 V/500 V two winding transformer has an efficiency of 95% at full load, unity power factor. If it is re-configured as a 500 V/750 V auto-transformer, its efficiency at its new rated load at unity power factor will be (A) 95.752% (B) 97.851% (C) 98.276% (D) 99.241%
Last Answer : A
Description : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is (A) 216 V (B) 226 V (C) 234 V (D) 236 V
Last Answer : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is 226 V
Description : A two -winding single phase transformer has a voltage regulation of 4.5% at full - load and unity power -factor. At full -load and 0.80 lagging power-factor, the voltage regulation will be: (A) 4.5% (B) less than 4.5% (C) more than 4.5% (D) none of the above
Last Answer : A two -winding single phase transformer has a voltage regulation of 4.5% at full - load and unity power -factor. At full -load and 0.80 lagging power-factor, the voltage regulation will be: more than 4.5%
Description : A transformer has negative voltage regulation when its load power factor is- (a) Zero (b) Unity (c) Leading (d) Lagging
Last Answer : Ans: C
Description : In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading.
Last Answer : (B) leading p.f.
Description : The main application of delta/zig-zag connected 3-phase transformer is to supply (A) balanced loads (B) unbalanced loads (C) furnace loads (D) single-phase loads
Last Answer : The main application of delta/zig-zag connected 3-phase transformer is to supply unbalanced loads
Description : Define transformation ratio of a transformer.
Last Answer : Transformation Ratio (K) of a transformer: It is the ratio of secondary number of turns to primary number of turns. (OR) It is the ratio of secondary voltage to primary voltage. (OR ) It is the ratio of primary current to secondary current. OR
Description : Define: 1) voltage ratio, 2) current ratio, 3) transformation ratio of transformer.
Last Answer : 1) Voltage ratio: The voltages in primary and secondary winding is proportional to number of turns in primary and secondary respectively. So, the voltage ratio is same as transformation ratio. V2/V1 = N2 ... as transformation ratio of transformer. It is denoted by K. K = N2/N1
Description : The voltage transformation ratio of a transformer is equal to the ratio of?
Last Answer : The voltage transformation ratio of a transformer is equal to the ratio of secondary induced e.m.f. to primary induced e.m.f.
Description : Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is?
Last Answer : Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is approximately equal to 1.
Description : Use of auto-transformer is economical when the transformation ratio is?
Last Answer : Use of auto-transformer is economical when the transformation ratio is near unity.
Description : Which of the following statements about a three-phase wye connection is correct? A. The line current is 1.73 times the phase current. B. The phase current is 1.73 times the line current. C. The line voltage is 1.73 times the phase voltage. D. The phase voltage is 1.73 times the line voltage.
Description : If the load p.f. is 0.866, then the average p.f. the v-bank is 1. 0.886 2. 0.75 3. 0.51 4. 0.65
Last Answer : If the load p.f. is 0.866, then the average p.f. the v-bank is 0.75
Description : Figure 'D' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts
Last Answer : Answer: A
Description : Figure 'C' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts
Description : Figure 'B' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts
Description : Figure 'A' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts
Description : In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter ... the windings D. help the windings to cool to the same temperature as the ground test connection
Description : In a three-phase, open-delta connected transformer, the line current is equal to _____________. A. the phase current B. three times the phase current C. the sum of any two phase currents D. the difference of any two phase currents
Description : What is voltage transformation ratio or turn ratio?
Last Answer : It is expressed as ratio of the primary and secondary voltages of transformer. or It is expressed as ratio of the primary and secondary turns of transformer. E1/ E2= T1/T2 = K
Description : The turns ratio of transformer 'A' shown in the illustration is four to one and all taps are evenly spaced. If 120 volts were applied to terminals 'H1' and 'H3', what would appear at 'X1' and 'X2'? EL-0082 A. 15 volts B. 30 volts C. 480 volts D. 960 volts
Description : At which frequency ratio, phase angle increases as damping factor increases? A. When frequency ratio is less than unity B. When frequency ratio is more than unity C. When frequency ratio is zero D. All of the above
Last Answer : A. When frequency ratio is less than unity
Description : While dissolving a gas into a liquid at a constant temperature, the ratio of the concentration of the gas in the solution phase and in the gaseous phase is (A) Infinity (B) Unity (C) Constant (D) Negative
Last Answer : (C) Constant
Description : The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V.
Last Answer : (C) 3.0 V.
Description : for Delta-Star connection of 3-phase transformer: i) Draw the connection diagram ii) List any two advantages of this connection iii) State its area of application.
Last Answer : Disadvantages: i) In this type of connection, the secondary voltage is not in phase with the primary. Hence it is not possible to operate this connection in parallel with star-star or delta-delta ... iv) As line current is equal to phase current the conductor size of winding should be large.
Description : State what is the significance of conducting phasing out test on a 3-phase transformer? Explain its procedure with a suitable connection diagram.
Last Answer : -Short primary & secondary winding of other phases expect the one under test. -Connect voltmeter to secondary winding. -A small DC current is circulated through the primary winding through ... . -The test repeated for finding out remaining concerned secondary windings in the same manner.
Last Answer : Advantages of open delta connection of 3-phase transformer: 1. When one of the phase in case of delta-delta bank is out of order by any reason, the service will be continued till ... demand in future (about 33%) will be supplied by converting open delta connection to delta-delta connection.
Description : Which three-phase connection can be used in a transformer to introduce a phase difference of 30o between its output and corresponding input line voltages (A) Star-Star (B) Star-Delta (C) Delta-Delta (D) Delta-Zigzag
Last Answer : Which three-phase connection can be used in a transformer to introduce a phase difference of 30o between its output and corresponding input line voltages (A) Star-Star (B) Star-Delta (C) Delta-Delta (D) Delta-Zigzag
Description : The transformer connection which has gained considerable popularity to serve 3-phase equipment and single phase lighting load is • Star/Star • Delta/Delta • Delta/Star • Star/Delta
Last Answer : The transformer connection which has gained considerable popularity to serve 3-phase equipment and single phase lighting load is Delta/Star
Description : Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines: (A) Delta-Star (B) Star-Delta (C) Delta-Delta (D) Star-Star
Last Answer : Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines: Star-Star
Description : For the liquid phase zero order irreversible reaction A → B, the conversion of A in a CSTR is found to be 0.3 at a space velocity of 0.1min -1 . What will be the conversion for a PFR with a space velocity of 0.2 min ... conditions are the same for CSTR and PFR. (A) 0.15 (B) 0.30 (C) 0.60 (D) 0.90
Last Answer : (C) 0.60
Description : Fatty acids can not be converted into carbohydrates in the body, as the following reaction is not possible: (A) Conversion of glucose-6-phosphate into glucose (B) Fructose 1, 6 diphosphate to ... phosphate (C) Transformation of acetyl CoA to pyruvate (D) Formation of acetyl CoA from fatty acids
Last Answer : Answer : C
Description : Fatty acids cannot be converted into carbohydrates in the body as the following reaction is not possible. (A) Conversion of glucose-6-phosphate into glucose (B) Fructose 1,6-bisphosphate to fructose- ... (C) Transformation of acetyl CoA to pyruvate (D) Formation of acetyl CoA from fatty acids
Last Answer : C