What is the primary function of a power transformer?
A To step down voltage for residential use
B To step up or step down high-voltage levels for power transmission
C To regulate the current in the system
D To prevent transformer overheating
Power transformers are used in power transmission systems to step up or step down voltage for efficient long-distance transmission. They are crucial for handling high power levels and ensuring the safe delivery of electrical energy across vast distances.
Which test is used to determine the efficiency of a transformer under load?
A Short-circuit test
B Open-circuit test
C Load test
D Insulation test
The load test is used to assess the transformer’s performance under actual operating conditions when supplying power to its rated load. It helps measure efficiency, voltage regulation, and heat generation during normal operation.
What does the equivalent circuit of a transformer represent?
A The physical construction of the transformer
B The electrical properties of the transformer in a simplified form
C The cooling system of the transformer
D The safety mechanisms in the transformer
The equivalent circuit of a transformer simplifies its electrical characteristics, such as resistance, inductance, and core losses. This model helps in analyzing the transformer’s behavior and performance during operation.
What is the primary cause of impedance in a transformer?
A The resistance of the windings
B The magnetizing current
C The leakage flux
D The turns ratio
Impedance in a transformer consists of both the resistance in the windings (copper loss) and reactance caused by the inductance of the windings. Impedance affects the current drawn and the voltage drop in the transformer.
What is the effect of harmonics on transformer operation?
A They increase the efficiency of the transformer
B They cause heating and increased losses
C They improve voltage regulation
D They reduce the transformer’s operational lifespan
Harmonics are higher-frequency components in the current waveform that cause distortion. They result in additional losses, heating, and reduced efficiency in transformers, making them harder to operate efficiently.
What is the purpose of an insulation resistance test on a transformer?
A To measure core losses
B To test the transformer’s insulation system
C To check the impedance of the transformer
D To evaluate the load capacity of the transformer
The insulation resistance test measures the resistance of the transformer’s insulation. It ensures that the insulation can withstand the operating voltage without breaking down, preventing electrical faults and transformer damage.
What is the role of a short-circuit test in transformer testing?
A To measure core losses
B To measure copper losses
C To check the insulation resistance
D To measure the efficiency of the transformer
The short-circuit test is performed to measure the copper losses in the transformer. This test involves short-circuiting the secondary winding and applying reduced voltage to the primary winding.
What is an earthing transformer used for?
A To step up voltage in a distribution system
B To provide a neutral point for grounding in an ungrounded system
C To step down voltage for residential use
D To reduce transformer size
An earthing transformer is used to provide a neutral point in systems without a neutral, such as in delta-connected systems. It is crucial for grounding, enhancing system stability, and protecting against faults.
Which of the following is a fault commonly found in transformers?
A Voltage regulation
B Overload fault
C Insulation breakdown
D All of the above
Overload faults, insulation breakdowns, and short circuits are common faults in transformers. Overloading leads to excessive current flow, causing damage, while insulation failure can result in short circuits or loss of operational integrity.
What is the role of a load test in transformer performance evaluation?
A To assess the transformer’s performance under actual load conditions
B To measure core losses
C To determine the copper losses
D To measure the efficiency of insulation
The load test measures a transformer’s performance when supplying its rated load. It helps evaluate how well the transformer maintains voltage regulation, handles power losses, and operates efficiently during real-world conditions.
What is the effect of harmonics on transformer operation?
A They improve transformer efficiency
B They cause heating and increased losses
C They improve voltage regulation
D They have no effect on transformer operation
Harmonics in transformer operation result in additional losses and heating. These distortions in the voltage and current waveforms reduce transformer efficiency and can cause overheating if not filtered out.
What is the function of an isolation transformer?
A To electrically isolate the primary and secondary circuits
B To step up or step down voltage
C To regulate voltage
D To measure current
Isolation transformers electrically isolate the primary and secondary circuits to prevent electrical noise, surges, or faults from being transmitted. They are commonly used in sensitive equipment like medical devices and computers.
What is the main advantage of parallel operation of transformers?
A It increases the overall system capacity and reliability
B It reduces voltage fluctuation
C It decreases transformer losses
D It steps up voltage
Parallel operation allows multiple transformers to share the load, increasing the overall capacity of the system. This improves reliability by ensuring that no single transformer is overloaded.
What is the typical efficiency range of modern transformers?
A 50-60%
B 70-80%
C 80-90%
D 90-98%
Modern transformers are designed to operate with high efficiency, typically ranging from 90% to 98%. This high efficiency is achieved by using high-quality materials and advanced designs to minimize losses like core and copper losses.
What is the function of the primary winding in a transformer?
A To generate magnetic flux
B To regulate voltage output
C To provide insulation
D To dissipate heat
The primary winding of a transformer is connected to the power source and generates the magnetic flux that is transferred to the secondary winding. This flux induces a voltage in the secondary winding based on the turns ratio.
What is the typical application of a distribution transformer?
A To step down voltage for residential and commercial use
B To step up voltage for transmission
C To regulate voltage in industrial applications
D To isolate electrical circuits
Distribution transformers are used to step down the voltage from high transmission levels to the lower voltages required for residential and commercial use. These transformers are commonly located in neighborhoods and industrial areas.
What is the purpose of the insulation resistance test in transformers?
A To test the condition of the transformer’s insulation
B To measure the transformer’s impedance
C To measure the core loss
D To test the transformer’s efficiency
The insulation resistance test checks the quality and strength of the transformer’s insulation system. This is critical for preventing electrical faults and ensuring the transformer can safely handle the rated voltage.
What is the typical frequency of transformers used in the power grid?
A 50 Hz or 60 Hz
B 100 Hz
C 200 Hz
D 500 Hz
Transformers used in power transmission systems typically operate at frequencies of 50 Hz or 60 Hz. These are standard frequencies for alternating current (AC) used in most countries worldwide.
What is the role of the secondary winding in a transformer?
A To generate magnetic flux
B To supply power to the load
C To regulate the voltage output
D To dissipate heat
The secondary winding of a transformer receives induced voltage from the primary winding and supplies power to the load. The voltage and current in the secondary winding depend on the turns ratio of the transformer.
What is the primary purpose of a voltage regulator transformer?
A To maintain a constant voltage under varying load conditions
B To step up voltage for long-distance transmission
C To regulate the transformer’s temperature
D To reduce current in the system
A voltage regulator transformer helps ensure that the voltage supplied to the load remains stable despite variations in the load. It automatically adjusts the voltage to meet the changing demand.