At what power factor does the transformer operates?
AAlways unity pf
BAlways lagging pf
CAlways leading pf
DAt a pf depending on load pf
Electrical Engineering · Question Bank
Transformers
110 of 258 questions match · page 4 of 6. Answer in your head first, then check the solution.
What is the purpose of the open circuit test in a transformer?
ATo determine full load copper loss
BTo determine total losses
CTo determine the iron loss
DTo determine the power output at no load
Transformer actions require which of the following fluxes?
AConstant magnetic flux
BAlternating magnetic flux
CPulsating magnetic flux
DNo flux is needed
What is being increased in a step up transformer?
AVoltage
BCurrent
CPower
DAll of these
What is the resistance of the low voltage winding in comparison to the high voltage winding in a transformer?
AIt is equal
BIt is less than
CIt is greater than
DIt can be less or greater, depending on usage of the transformer
When a transformer winding suffers a short circuit, what type of force will be experienced by the adjoining turns of the same winding?
AAn attractive force
BA repulsive force
CZero or no force
DAny of these
Instrument transformers are used on AC circuits for extending the range of which of the following instruments?
AAmmeter
BVoltmeter
CWattmeter
DAll of these
The eddy current loss in a transformer varies ____ the supply voltage.
AInversely with
BDirectly with
CInversely to the square of
DDirectly to the square of
What will happen to the transformer if the primary is connected to a dc supply?
AThe core loss will increase
BThe primary may get burned out
CThe primary will draw less current
DNothing serious will happen
Which part of the transformer is most subjected to damage due to overheating?
AIron core
BFrame or casing
CWinding insulation
DCopper windings
What is a conservator in a transformer?
AIt is an air-tight metal drum located at the top of a transformer tank
BIt is the metal tank of a transformer that houses the core and the windings
CIt is a protective device that protects the transformer from overloading
DIt is a protective device that protects the transformer from lightning surges
In a transformer, at every instant the direction of the secondary current must be such as to oppose any change in flux. This is based on which of the following principles?
ACoulomb's law
BFaraday's law
CJoule's law
DLenz's law
Which one is the most common cause of contamination of water in the oil used in transformer located indoors?
ALeaky bushings
BCondensation of moisture from air in the tank
CDecomposition of foreign matters in the oil
DNone of these
What is the main function of the iron core in a transformer?
ATo provide mechanical strength to the windings
BTo reduce the eddy current loss
CTo provide electrical linkage to the two windings
DTo reduce the reluctance of the magnetic path
What is the relationship between the induced emf and the core flux in a transformer?
AThe induced emf lags the core flux by 90°
BThe induced emf leads the core flux by 90°
CThe induced emf is in-phase with the core flux
DThe induced emf is independent of the core flux
What is the typical usage of an autotransformer?
ACurrent transformer
BVariable transformer
CIsolating transformer
DControl transformer
As compared to A-A transformer bank, what is the percentage capacity of the V-V bank?
A66.7%
B86.6%
C57.7%
D73.3%
What is the reason why transformers operate poorly at very low frequencies?
AMagnetizing current is high
BPermeability of the core will increase
CPrimary reactance is too much increased
DCopper loss is high
What is the main purpose of having a core in a transformer?
ATo decrease the iron losses
BTo prevent the eddy current loss to happen
CTo eliminate the magnetic hysteresis
DTo decrease the reluctance of the common magnetic circuit
What type of coupling is used in the primary and secondary windings of a transformer?
AElectrical
BMechanical
CMagnetic
DAll of these
More Electrical Engineering topics
- 1-Phase AC Circuits115
- 1P AC Circuits161
- 3-Phase AC Circuits83
- 3-Phase Induction Motors46
- 3P AC Circuits71
- 3P Induction Motors135
- Alternators157
- Basic Principles30
- circuits301
- Communications408
- Converters & Rectifiers59
- DC Circuits52
- DC Electric Circuits84
- DC Generators196
- DC Motors285
- Electrical Power Plant195
- Electrical Transients72
- Electromagnetic Induction68
- Electromagnetics350
- Electronics433
- Electrostatics100
- Energy Conversion357
- Engineering Materials117
- Faults106
- Fundamentals of Electricity141
- Illumination143
- Industrial Electronics205
- Instrumentation224
- Instruments & Measurements94
- Instruments and Measurements33
- Laws113
- Magnetic Circuits84
- Magnetism24
- Miscellaneous83
- Miscellaneous Topics33
- Network Laws & Theorems9
- Non-Sinusoidal Waveforms13
- Philippine Electrical Code33
- Power Factor Correction38
- Power Factor Corrections23
- Power Systems32
- Synchronous Motors112
- Transmission Lines168