Description : Mention the important parts of a power transformer and their purposes.
Last Answer : Conservator: This allows for shrinkage and swelling of transformer oil. When the oil is heated up it swells and rises to the conservator. When cools down it goes back to main tank. Conservator reduces sludge ... put. There are two types of tap changer. Online tap changer and off line tap changer.
Description : What are the purposes or advantages of transformer?
Last Answer : Purposes a. Electrical energy may be transmitted economically over long distance by stepping up of voltages to reduce the line losses. b. To distribute the low voltages at consumer side by stepping down ... There by efficiency is high and about 95 to 98%. b. Practically maintenance is very less.
Description : A switchboard for an AC electrical system requires the use of which of the following devices? A. Frequency meter. B. Ohmmeter. C. Induction voltage regulator. D. Current transformer governor.
Last Answer : Answer: A
Description : What are the purposes of the transformer in a power supply?
Last Answer : It couples the power supply to the ac line voltage, isolates the ac line voltage from the load, and steps this voltage up or down to the desired level.
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 : In conversion of 3-phase to 2-phase supply with T connection, the transformation ratio of the teaser will be__ times to that of main transformer: a) 1.732 b) 1.15 c) 0.866 d) Unity
Last Answer : Ans: C
Description : A load with an impedance of 440 ohms is connected across the secondary of the transformer illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given
Last Answer : Answer: B
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 : A load is connected to the secondary of the transformer illustrated and the current through the load is 10 amps. If the step-up ratio is 10 to 1 and the input voltage is 110 VAC, what will be the current flow through the primary? EL-0055 A. 1 amp B. 10 amps C. 100 amps D. 1000 amps
Last Answer : Answer: C
Description : In the illustrated circuit, if the input to leads 'B' and 'Y' was 24 VDC the output between 'A' and 'X' will be _________. EL-0069 A. 24 VDC B. 22.8 VDC, 24 VDC minus the 1.2 VDC voltage drop across two diodes C. undeterminable without knowing the turns ratio of the transformer D. 0 VDC
Last Answer : Answer: D
Description : What is the maximum current allowed to be drawn from the secondary of a 2 KVA step-down transformer with a turns ratio of four to one if connected across a 440 volt line? A. 1.1 amps B. 4.5 amps C. 18.1 amps D. 22.7 amps
Description : What is the maximum allowable primary current of a 2 KVA step-down transformer with a four to one turns ratio if connected across a 440 volt line? A. 1.1 amps B. 4.5 amps C. 18.1 amps D. 27.7 amps
Description : What is voltage ratio of a transformer?
Last Answer : A. Voltage ratio is the ratio of the voltage between the line terminals of one winding to that between the line terminals of another winding at no load.
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 : 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 : For practical purposes, in a simple series circuit, the source voltage will be dropped across one resistor if it has ______________. A. half the resistance of the other resistor B. a resistance equal to the other C. at least ten times the resistance of the other D. a partial short circuit
Description : Which of the following statements is true concerning a polyphase synchronous propulsion motor? A. The motor is started as an induction motor. B. Resistance is gradually added to the rotor circuit. C. ... is held below the rated current. D. The field winding is energized for starting purposes only.
Description : What are the purposes of cable trays?
Last Answer : a. Avoid sagging of cables b. Give mechanical support
Description : What type of governing system used in turbine and what are the purposes of the system?
Last Answer : Hydraulic governing system of centrifugal (speed) governer type is adopted in turbine. Sensitive oil pressure to actuate centrifugal governer is 6.1 kg/cm2 (max). At 6.7 kg/cm2 relief valve ... speeder gear from BPC signal. Once synchronised the grid frequency and speeder gear controls the speed.
Description : What are the purposes of barring gear?
Last Answer : Start rotor from rest. Eliminates sag in rotor - straighten and avoid rubbing at glands. Avoid direct contact journals and bearings. Avoid differential temp between top and bottom of cylinder due to convection of Steam or hot air inside turbine cylinders.
Description : What are the purposes of bleed condenser?
Last Answer : The purposes of bleed condenser are, a. To cool the bleed water, which goes to bleed cooler. b. To provide cool hot water to the PHT purification system.
Description : What are the purposes of turning gear?
Last Answer : Turning gear is used to run the turbine from rest to low speed and from normal running speed to low speed with the help of barring motor to eliminate the hogging and sagging of turbine because of the high temperature.
Description : An alternator switchboard has a synchroscope and synchronizing lamps. If the synchroscope is broken, which of the steps listed is the most essential before an alternator can be paralleled with the bus? ... D. A portable phase sequence indicator must be used to verify the information from the lamps.
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 : A three-phase alternator operates at 450 volts with a power factor of 0.8. If the ammeter indicates 250 amperes, what should be the KW meter reading? A. 90.00 KW B. 127.27 KW C. 155.70 KW D. 194.85 KW
Description : A three-phase alternator is developing 300 amps, with a 0.8 power factor, at 450 volts. The true indicated power on the kilowatt meter, located on the main switchboard, will be ____________. A. 133 kw B. 155 kw C. 187 kw D. 212 kw
Description : When a megohmmeter is being used on a alternating current machine, the meter pointer will dip toward 'zero' and then gradually rise to the true resistance value if the motor insulation is _____________. A. grounded B. good C. shorted D. dirty
Description : A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter would then read ____________. A. 181.4 KW B. 186.8 KW C. 194.2 KW D. 201.4 KW
Description : The reading at 'X' while on the R X 100 meter scale illustrated would be ______. EL-0047 A. 8 ohms B. 150 ohms C. 800 ohms D. 80,000 ohms
Description : On some electrical generating equipment one outboard bearing pedestal is insulated from the bedplate. To check this insulation with the machine assembled you should use a____________. A. millivolt meter and a jumper B. ohmmeter C. megohm meter D. high potential tester
Description : A switchboard ammeter indicates a reading slightly above 'zero' when the leads are disconnected, this is caused by _____________. A. mechanical misalignment of the meter pointer B. a poor ground for the meter case C. static electricity in the air D. capacitors inside the meter storing charges
Description : On some electrical generating equipment one outboard bearing pedestal is insulated from the bedplate. This should be checked with a millivolt meter and a jumper. With the millivolt meter connectd between ... then removed to take a second reading. This eliminates the insulating effect of the bearing.
Description : On some electrical generating equipment one outboard bearing pedestal is insulated from the bedplate. To check this insulation with the machine assembled you should use a____________. A. ohmmeter with the ... C. megohm meter with the machine running D. voltmeter and ampmeter with the machine running
Description : On the meter scale illustrated, while using the R X 100 scale, the reading at 'Z' is___________. EL-0047 A. 3,000 ohms B. 30,000 ohms C. 300,000 ohms D. 3,000,000 ohms
Description : If reading AC current with the illustrated device and unsure of the range as a precaution , the first step should be to _________. EL-0047 A. secure power and test for voltage B. disconnect the ... resistance and use Ohm's law to calculate current D. unable to safely measure current with the device
Description : A voltmeter located on a control panel has been operating correctly for six months, suddenly burns out. After removing it, it is found that neither side of the meter has been grounded. When ... side and the ground C. installed exactly as the old installation D. grounded to the positive side
Description : A current carrying conductor making an electrical contact with a wiring metal conduit is indicated by a _____________. A. low switchboard wattmeter reading B. reading of 1.0 on the power factor meter C. high switchboard voltmeter reading D. totally darkened switchboard ground-detecting light
Description : On the meter scale illustrated, while using the R X 1 scale, the reading at 'E' will be ____________. EL-0047 A. 2.0 ohms B. 20 ohms C. 200 ohms D. none of the above
Description : On the meter scale illustrated, while using the R X 1 scale, the reading at 'F' will be ____________. EL-0047 A. 1.8 ohms B. 6.0 ohms C. 9.4 ohms D. 0.6 ohms
Description : The illustrated circuit is a wheatstone bridge. If the meter 'G' reads 0 with the switch closed then ________. EL-0024 A. the current through R1 - R2 is equal to the current through R3 - Rx B. the voltage ... of E C. the resistance of Rx is equal to the resistance of R2 D. all the above are true
Description : If the voltage applied to a moving disk frequency meter decreases, while the applied frequency remains the same, the frequency indication will _____________. A. increase B. decrease C. remain the same D. oscillate
Description : If reading the AC voltage from the line lead of a 440 VAC controller the range switch illustrated should be set to ___________. EL-0047 A. 1,000 V B. 250 V C. R X 10,000 D. Unable to safely read with this meter.
Description : On the meter scale illustrated, while using the R X 1 scale, the reading at 'Z' will be ____________. EL-0047 A. 30 ohms B. 72 ohms C. 720 ohms D. 7.2 Kohms
Description : On the meter scale illustrated, while using the R X 100 scale, the reading at 'F' will be ____________. EL-0047 A. 60 ohms B. 40 ohms C. 30 ohms D. 3 kohms
Description : On the meter scale illustrated, while using the R X 100 scale, the reading at 'B' will be ____________. EL-0047 A. 70 ohms B. 35 ohms C. 700 ohms D. 7 kohms
Description : On the meter scale illustrated, while using the R X 100 scale, the reading at 'C' will be ____________. EL-0047 A. 13 ohms B. 130 ohms C. 1.3 kohms D. 13 kohms
Description : On the meter scale illustrated, while using the R X 100 scale, the reading at 'D' will be ____________. EL-0047 A. 3.6 ohms B. 36 ohms C. 193 ohms D. 360 ohms
Description : Which of the following electric meter movements uses a stationary permanent magnet and movable coil? A. D'Arsonval B. Electrodynamometer C. Moving iron-vane D. Inclined coil iron-vane