This method is time consuming, but only requires a voltage source, a resistance, and a voltmeter. In the transformer the function of a conservator is to a provide fresh air for cooling the transformer b supply cooling oil to transformer in time of need c protect the transformer from damage when oil expends due to heating d none of the above Ans: c 27. For given applied voltage, with the increase in frequency of the applied voltage a eddy current loss will decrease b eddy current loss will increase c eddy current loss will remain unchanged d none of the above Ans: c 108. After you've replaced the transformer, observe it to make sure this does not happen. These several connections give various magnitudes and phase of the secondary voltage; the magnitude can be adjusted for parallel operation by suitable choice of turn ratio, but the phase divergence cannot be compensated. A transformer has a 3 to 2 ratio. Distribution transformers are generally designed for maximum efficiency around a 90% load b zero load c 25% load d 50% load Ans: d 58.
The test voltage shall be limited to maximum power supply voltage available at site. The characteristics of non-linear loads that they demand current only during part of the cycle creates harmonic effects. Which of the following properties is not necessarily desirable for the material for transformer core? In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are a hysteresis and eddy current losses b friction and windage losses c copper losses d none of the above Ans: a 110. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not work. This is its electrical input.
Electrical Theory Practice Tests Consists of Practice Tests including Ohms Law, Resistors, Inductors, Capacitors, Series and Parallel Circuits, Transformers and Electrical Motors, Power Factor, Different Measuring Instruments, Units of Measurement, Circuit Breakers, Relays, Motor Control Centers and many more. The leakage flux in a transformer depends upon a load current b load current and voltage c load current, voltage and frequency d load current, voltage, frequency and power factor Ans: a 66. More update please subscribe my channel Learning Engineering. No-load on a transformer is carried out to determine a copper loss b magnetising current c magnetising current and loss d efficiency of the transformer Ans: c 8. What would be the secondary terminal markings? Check 7 During erection, the exposure of active part of transformers should be minimized. In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are a friction and windage losses b copper losses c hysteresis and eddy current losses d none of the above Ans: c 23.
Spacers are provided between adjacent coils a to provide free passage to the cooling oil b to insulate the coils from each other c both a and b d none of the above Ans: a 33. The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer a Conservator b Breather c Bushings d Buchholz relay Ans: a 82. All the transformers with the same vector ground have same phase sequence and phase divergence between primary and secondary. The acceptable criteria should be the measured impedance voltage having agreement to within 3 percent of impedance specified in rating and diagram nameplate of the transformer. In a power or distribution transformer about 10 per cent end turns are heavily insulated a to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns b to absorb the line surge voltage and save the winding of transformer from damage c to reflect the line surge and save the winding of a transformer from damage d none of the above Ans: a 107. The chemical used in breather for transformer should have the quality of a ionizing air b absorbing moisture c cleansing the transformer oil d cooling the transformer oil.
In a transformer the tappings are generally provided on a primary side b secondary side c low voltage side d high voltage side Ans: c 41. Noise level test in a transformer is a a special test b routine test c type test d none of the above Ans: c 68. Taking care to observe proper polarity is important when installing and connecting current transformer to power metering and. Confirm the proper input to the transformer. Transformer breaths in when a load on it increases b load on it decreases c load remains constant d none of the above Ans: b 31. Check 4 Unpacking and inspection of accessories to be carried out taking all precautions so that the tools used for opening do not cause damage to the contents.
If you hear sounds like these, cut power to the transformer to prevent burnout. One phase winding is wound in one limb. Primary and Secondary Voltage 5. Measurement of turn ratio is based on, applying a to one of the windings using a bridge equipment and measuring the ratio of the induced voltage at the bridge. The highest voltage for transmitting electrical power in India is a 33 kV. It is changed until a balance occurs on the % error indicator. Remove inputs and outputs to determine the source of the failure.
A transformer can have zero voltage regulation at a leading power factor b lagging power factor c unity power factor d zero power factor Ans: a 70. An agreement to within 30% of the measured exciting current with the previous test is usually considered satisfactory. The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer a Conservator b Breather c Bushings d Buchholz relay Ans: a 82. It is also done at site to ensure healthiness of a transformer that is to check loose connections, broken strands of conductor, high contact in tap changers, high leads and bushings etc. Here you can find objective type Electrical Engineering Transformers questions and answers for interview and entrance examination.
Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is a approximately equal to one b less than one c great than one d none of the above Ans: a 138. Both reactive and resistive power contribute to temperature rise in a transformer. When the current passes through zero and begins to go into the negative, the current is reversed. These tests are done to assess the condition of transformer after installation and compare the test results of all the low tests with the factory test reports. Harmonics in transformer result in a increased core losses b increased I2R losses c magnetic interference with communication circuits d all of the above Ans: d 72.
Which of the following is the most likely source of harmonics in a transformer? Figure 3 — Connection group representation and measuring 1. To learn how to troubleshoot your transformer, keep reading! A transformer core is laminated to a reduce hysteresis loss b reduce eddy current losses c reduce copper losses d reduce all above losses Ans: b 4. For confirming the specifications and performances of an it has to go through a number of testing procedures. Figure 7 — Graph depicting variation of N2 gas pressure w. The chemical used in breather for transformer should have the quality of a ionizing air b absorbing moisture c cleansing the transformer oil d cooling the transformer oil.
If the input power climbs to the expected value, the primary of the transformer is bad. When a given transformer is run at its rated voltage but reduced frequency, its a flux density remains unaffected b iron losses are reduced c core flux density is reduced d core flux density is increased Ans: d 84. Measure the secondary output of the transformer. This measurement may be performed using conventional analog rarely used nowadays or digital meters. This is often stated as number of turns of wire. If the measurement is less than 80 percent of the expected voltage, the fault could lie in either the transformer or the circuitry providing the primary with power.