What is the purpose of using a laminated core in transformers?
A Increase voltage
B Decrease impedance
C Reduce eddy currents
D Increase efficiency
Laminated cores are used in transformers to reduce eddy current losses. The thin sheets of metal are insulated from each other, which restricts the flow of circulating currents, minimizing energy loss and improving efficiency.
In a single-phase transformer, what is the primary function of the core?
A Support windings
B Transfer energy
C Store energy
D Provide insulation
The core of a single-phase transformer primarily supports the windings and provides a path for the magnetic flux. It helps efficiently transfer the magnetic energy between the primary and secondary windings without energy loss.
What is the primary advantage of using a three-phase transformer over a single-phase transformer in power systems?
A Simpler construction
B Cost efficiency
C Lower voltage
D Higher efficiency
A three-phase transformer offers higher efficiency compared to a single-phase transformer due to the continuous delivery of power, reduced fluctuations in current, and better utilization of materials, which results in more compact and cost-effective designs.
What does voltage regulation in a transformer measure?
A Current under load
B Voltage drop under load
C Voltage at no load
D Efficiency under load
Voltage regulation measures the change in the secondary voltage from no-load to full-load conditions. It indicates how much the voltage decreases as the transformer supplies current, reflecting the transformer’s ability to maintain stable voltage under varying loads.
What is the main function of the windings in a transformer?
A Control current
B Provide voltage regulation
C Generate magnetic field
D Generate heat
The windings in a transformer generate a magnetic field when current flows through them. This magnetic field is essential for transferring energy from the primary winding to the secondary winding, which induces voltage and allows power transfer.
Which of the following is a common method used for cooling in oil-filled transformers?
A Oil circulation
B Cryogenic cooling
C Air cooling
D Water cooling
In oil-filled transformers, oil circulation is used for cooling. The oil absorbs heat generated by the windings and core, and is then cooled by radiators or external cooling systems. This process ensures the transformer operates at safe temperatures.
What is the typical use of dry-type transformers?
A Offshore platforms
B Power transmission
C High-power applications
D Indoor installations
Dry-type transformers are commonly used in indoor installations due to their lack of oil, reducing the risk of leaks or fires. They are preferred for areas where oil-filled transformers would pose safety concerns, such as in commercial or residential buildings.
Which core material is commonly used in transformer construction?
A Iron
B Silicon steel
C Copper
D Aluminum
Silicon steel is commonly used in transformer cores because it has high magnetic permeability, which allows for efficient magnetic flux conduction. The silicon content reduces core losses, improving transformer efficiency and reducing energy loss.
In a three-phase transformer, what is the typical configuration used for load distribution?
A Delta-Star
B Star-Delta
C Delta-Delta
D Star-Star
The Delta-Star configuration is commonly used in three-phase transformers to provide balanced load distribution and allow for step-up or step-down voltage conversion. The delta side provides higher current capacity, while the star side provides a neutral for grounding.
What is the effect of transformer losses on efficiency?
A Losses improve voltage
B Losses have no effect
C Losses decrease efficiency
D Losses increase efficiency
Transformer losses, including core losses (hysteresis and eddy currents) and copper losses (due to resistance in the windings), reduce the overall efficiency. These losses convert some of the input electrical energy into heat, decreasing the transformer’s ability to deliver useful power.
Which type of transformer is used to maintain a stable voltage in sensitive applications?
A Autotransformer
B Step-up transformer
C Isolation transformer
D Distribution transformer
Isolation transformers are used in sensitive applications to maintain a stable voltage and isolate the load from the power source. They prevent electrical noise, surges, and ground loops, making them ideal for equipment such as medical devices and laboratory instruments.
What causes the magnetizing current in a transformer?
A Leakage reactance
B Magnetic flux
C Load conditions
D High voltage
The magnetizing current is the current required to establish the magnetic flux in the transformer’s core. It is a small current compared to the load current, and it is responsible for inducing voltage in the secondary winding.
What is one key benefit of using parallel transformers?
A Shared load capacity
B Lower voltage
C Higher efficiency
D Reduced losses
Parallel transformers share the load between them, improving system reliability and reducing the likelihood of overloading a single transformer. This allows for higher overall load capacity and better performance under varying demand conditions.
What is the role of a tap changer in a transformer?
A Increase impedance
B Change current
C Regulate load
D Adjust voltage
A tap changer is used to adjust the transformer’s output voltage by selecting different tap points on the windings. This allows for voltage regulation, ensuring that the voltage remains within acceptable limits despite load variations.
What is the purpose of the conservator tank in an oil-filled transformer?
A Increase voltage
B Filter oil
C Store extra oil
D Prevent overheating
The conservator tank in an oil-filled transformer stores extra oil to accommodate the expansion and contraction of oil due to temperature changes. This helps maintain the correct oil level and prevents pressure build-up, ensuring safe and efficient transformer operation.