What is the main purpose of a step-up transformer?
A To reduce current
B To increase voltage
C To step down voltage
D To convert AC to DC
A step-up transformer increases the voltage from the primary to the secondary side. It is commonly used in power transmission systems to reduce current and minimize energy losses over long distances.
Which type of transformer is used to isolate two circuits electrically?
A Power transformer
B Isolation transformer
C Autotransformer
D Distribution transformer
An isolation transformer is used to provide electrical isolation between the primary and secondary circuits. It protects sensitive equipment from power spikes and faults while reducing noise and interference.
What is the primary characteristic of a dry-type transformer?
A It uses oil for cooling
B It uses air for cooling
C It operates with high voltages only
D It is designed for outdoor use
Dry-type transformers use air for cooling instead of oil. They are typically used in environments where fire safety is a concern, such as in residential, commercial, or indoor industrial areas.
Which of the following is the most common loss in a transformer?
A Core loss
B Copper loss
C Dielectric loss
D Heat loss
Copper loss occurs due to the resistance of the windings in the transformer. When current flows through the copper windings, energy is dissipated as heat, which contributes to the overall energy losses in a transformer.
What is the primary function of the core in a transformer?
A To store electrical energy
B To provide a low-reluctance path for magnetic flux
C To regulate voltage
D To cool the transformer
The core of a transformer provides a low-reluctance path for the magnetic flux generated by the primary winding. It helps to direct the magnetic flux efficiently to the secondary winding, where it induces voltage.
What type of transformer is typically used for low-voltage applications such as residential power supply?
A Step-up transformer
B Distribution transformer
C Isolation transformer
D Power transformer
Distribution transformers are used to step down the voltage from high transmission levels to the lower levels used for residential power supply. These transformers are commonly found in substations and near residential areas.
What is the characteristic of magnetizing current in a transformer?
A It causes heat loss
B It is required to establish the magnetic field in the core
C It flows through the secondary winding
D It decreases with an increase in load
Magnetizing current is the small current drawn by the primary winding when the transformer is under no load. This current is essential for establishing the magnetic field in the transformer’s core and for its operation.
What does a short-circuit test on a transformer measure?
A Core loss
B Copper loss
C Efficiency
D Voltage regulation
The short-circuit test is conducted to measure the copper losses, which are caused by the resistance in the windings. During this test, the secondary side of the transformer is shorted, and the primary side is supplied with a reduced voltage.
What is inrush current in a transformer?
A The steady-state current during normal operation
B The surge of current that occurs when a transformer is energized
C The current required to heat the core
D The current caused by a fault condition
Inrush current is a large surge of current that occurs when a transformer is first connected to the electrical supply. This surge is due to the magnetization of the transformer’s core and can be many times higher than the normal operating current.
Which type of transformer is used to step up the voltage for long-distance power transmission?
A Isolation transformer
B Power transformer
C Step-down transformer
D Autotransformer
Power transformers are used to either step up or step down the voltage in power transmission systems. They are specifically used to step up the voltage for efficient long-distance transmission, reducing current and minimizing losses.
What is the role of the secondary winding in a transformer?
A To regulate the voltage
B To supply power to the load
C To induce current in the core
D To cool the transformer
The secondary winding of a transformer receives the induced voltage from the primary winding and supplies the power to the load. The voltage and current in the secondary depend on the turns ratio and the load characteristics.
What is the purpose of a tap changer in a transformer?
A To change the primary winding
B To adjust the voltage output
C To measure current
D To cool the transformer
A tap changer allows a transformer to adjust its voltage output by selecting different taps on the windings, enabling better voltage regulation in response to varying load conditions.
What happens to the efficiency of a transformer as the load increases?
A It decreases
B It increases
C It remains constant
D It fluctuates
The efficiency of a transformer typically increases as the load increases, provided the transformer operates within its rated capacity. The transformer operates most efficiently at full load, where losses are minimized.
What is the characteristic of magnetizing current in a transformer?
A It causes heat loss
B It is required to establish the magnetic field in the core
C It flows through the secondary winding
D It decreases with an increase in load
Magnetizing current is the small current drawn by the primary winding when the transformer is under no load. This current is essential for establishing the magnetic field in the transformer’s core and for its operation.
What does a short-circuit test on a transformer measure?
A Core loss
B Copper loss
C Efficiency
D Voltage regulation
The short-circuit test is conducted to measure the copper losses, which are caused by the resistance in the windings. During this test, the secondary side of the transformer is shorted, and the primary side is supplied with a reduced voltage.
What type of transformer is typically used for low-voltage applications such as residential power supply?
A Step-up transformer
B Distribution transformer
C Isolation transformer
D Power transformer
Distribution transformers are used to step down the voltage from high transmission levels to the lower levels used for residential power supply. These transformers are commonly found in substations and near residential areas.
What is the characteristic of magnetizing current in a transformer?
A It causes heat loss
B It is required to establish the magnetic field in the core
C It flows through the secondary winding
D It decreases with an increase in load
Magnetizing current is the small current drawn by the primary winding when the transformer is under no load. This current is essential for establishing the magnetic field in the transformer’s core and for its operation.
What does a short-circuit test on a transformer measure?
A Core loss
B Copper loss
C Efficiency
D Voltage regulation
The short-circuit test is conducted to measure the copper losses, which are caused by the resistance in the windings. During this test, the secondary side of the transformer is shorted, and the primary side is supplied with a reduced voltage.
What happens to the efficiency of a transformer as the load increases?
A It decreases
B It increases
C It remains constant
D It fluctuates
The efficiency of a transformer typically increases as the load increases, provided the transformer operates within its rated capacity. The transformer operates most efficiently at full load, where losses are minimized.
What is the characteristic of a step-down transformer?
A It increases voltage
B It decreases voltage
C It provides electrical isolation
D It increases current
A step-down transformer reduces the voltage from the primary to the secondary side. It is used in power distribution to lower voltage levels to those suitable for residential and industrial use.
What is the main purpose of a step-down transformer?
A To increase voltage
B To decrease voltage
C To increase current
D To decrease current
A step-down transformer is used to reduce the voltage from a higher level to a lower level. This is crucial in power distribution systems, where high-voltage transmission is needed to minimize loss, and lower voltage is required for safe use in homes and businesses.
Which type of transformer is used to isolate two circuits electrically?
A Power transformer
B Isolation transformer
C Autotransformer
D Distribution transformer
An isolation transformer is used to electrically isolate two circuits. It provides safety by preventing faults in one circuit from affecting the other, which is especially important in sensitive equipment like medical devices or audio systems.
What is the primary characteristic of dry-type transformers?
A They use liquid for cooling
B They are cooled by air and do not require oil
C They are designed for high-voltage applications only
D They are only used for industrial applications
Dry-type transformers do not use oil or other liquids for cooling. Instead, they rely on air to dissipate heat. These transformers are typically safer to use in areas where fire risk is a concern, such as residential or commercial buildings.
What is the purpose of using oil-filled transformers?
A To increase the current
B To provide insulation and cooling
C To regulate voltage
D To reduce magnetizing current
Oil-filled transformers use oil to both insulate the windings and to cool the transformer. The oil prevents arcing between windings and helps transfer heat from the core, improving transformer efficiency and safety.
Which of the following losses is caused by the resistance of the transformer windings?
A Copper loss
B Core loss
C Dielectric loss
D Hysteresis loss
Copper loss occurs due to the resistance in the transformer windings. As current flows through the copper windings, energy is dissipated in the form of heat, resulting in losses. This is a common source of energy loss in transformers.
What is the primary purpose of the core in a transformer?
A To store electrical energy
B To provide a low-reluctance path for magnetic flux
C To regulate the voltage
D To cool the transformer
The core in a transformer serves to provide a path for the magnetic flux generated by the primary winding. The core is made of materials with high magnetic permeability, such as silicon steel, to enhance the efficiency of electromagnetic induction.
What is the function of a tap changer in a transformer?
A To regulate the temperature of the transformer
B To adjust the voltage output under varying load conditions
C To change the turns ratio for voltage regulation
D To cool the transformer
A tap changer allows the transformer to adjust its output voltage by selecting different taps on the windings, enabling the transformer to handle variations in load while maintaining a stable voltage.
What is the purpose of a short-circuit test on a transformer?
A To measure core loss
B To calculate copper loss
C To measure insulation resistance
D To evaluate voltage regulation
The short-circuit test is used to measure copper losses in a transformer by applying a reduced voltage to the primary side while shorting the secondary side. The resulting power loss is directly related to the resistance in the windings.
What is the purpose of a distribution transformer?
A To step down voltage for residential use
B To step up voltage for transmission lines
C To isolate circuits
D To regulate voltage across a power system
A distribution transformer is used to step down the voltage from the high transmission level to a lower level suitable for residential and commercial use. It is an essential part of the distribution network.
What is the characteristic of magnetizing current in a transformer?
A It flows through the secondary winding
B It is required to establish the magnetic field in the core
C It is the current flowing to the load
D It is the current required to maintain efficiency
Magnetizing current is the small current drawn by the primary winding under no-load conditions. It is necessary to establish the magnetic field in the core for the transformer to operate.
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
D To dissipate heat
The secondary winding receives induced voltage from the primary winding and supplies power to the connected load. The voltage and current are determined by the turns ratio and the load characteristics.
Which type of transformer is used to convert high-voltage transmission lines to usable power levels for homes and businesses?
A Isolation transformer
B Step-down transformer
C Step-up transformer
D Power transformer
A step-down transformer reduces the high transmission voltage to a lower level, making it suitable for residential and commercial use. This is essential for delivering safe electrical power to consumers.
What is the primary role of a transformer’s core?
A To guide the magnetic flux generated by the primary winding
B To cool the transformer
C To increase the voltage
D To isolate the windings
The core of a transformer provides a low-reluctance path for the magnetic flux generated by the primary winding. It ensures efficient electromagnetic induction, which is crucial for transferring energy from the primary to the secondary winding.
What is the characteristic feature of an oil-filled transformer?
A It uses oil as both insulation and cooling medium
B It uses only air for cooling
C It operates at low voltages only
D It does not require insulation
Oil-filled transformers use oil both as an insulating material and as a coolant. The oil helps prevent arcing between windings and assists in dissipating the heat generated during operation, keeping the transformer safe and efficient.
What type of transformer is typically used in power generation plants to increase the voltage for transmission?
A Step-up transformer
B Step-down transformer
C Isolation transformer
D Distribution transformer
Step-up transformers are used in power plants to increase the voltage to high levels for long-distance transmission. This helps reduce the current and minimize energy losses during transmission.
Which of the following is the main advantage of using a dry-type transformer in indoor applications?
A It eliminates the risk of oil leaks and fire
B It increases the voltage efficiency
C It is cheaper to install
D It is easier to maintain
Dry-type transformers do not use oil, which eliminates the risk of oil leaks and fire. They are safer for use in indoor spaces like commercial buildings and residential areas where fire safety is a concern.
What does “magnetizing current” refer to in a transformer?
A The small current required to establish the magnetic field
B The current that flows through the secondary winding
C The current drawn by the load
D The current caused by a short circuit
Magnetizing current is the small current that flows in the primary winding of a transformer when it is energized. It is required to establish the magnetic field in the core for the transformer to function.
What is the primary advantage of using a three-phase transformer in large-scale power systems?
A It is more efficient and can handle larger loads
B It is cheaper and easier to maintain
C It can only operate at lower voltages
D It provides electrical isolation
Three-phase transformers are more efficient for transmitting large amounts of power over long distances. They can handle larger loads compared to single-phase transformers, making them ideal for industrial and commercial power distribution.
What is the purpose of using a tap changer in a transformer?
A To adjust the voltage output under varying load conditions
B To regulate the temperature of the transformer
C To change the turns ratio for voltage regulation
D To prevent overload
A tap changer allows the transformer to adjust the voltage by selecting different taps on the winding. This helps in maintaining a stable voltage despite changes in load.
What happens when a transformer is energized with excessive inrush current?
A It operates more efficiently
B It may cause damage to the transformer due to excessive heat
C It improves voltage regulation
D It reduces copper loss
Excessive inrush current can cause damage to the transformer’s windings and insulation due to the large surge of current when the transformer is first energized. This surge can lead to overheating and premature failure.
What is the function of the equivalent circuit of a transformer?
A To represent the electrical characteristics of the transformer in simplified form
B To calculate the power losses
C To measure the temperature
D To improve the efficiency of the transformer
The equivalent circuit of a transformer is a simplified model that represents the electrical characteristics, such as resistance, inductance, and magnetizing reactance, of the transformer. It helps in understanding and analyzing the transformer’s behavior during operation.
What does the impedance of a transformer represent?
A The efficiency of the transformer
B The opposition to the flow of current in the transformer windings
C The amount of power transmitted through the transformer
D The voltage regulation of the transformer
Impedance in a transformer refers to the total opposition to alternating current, consisting of both resistance and reactance. It affects the current drawn by the transformer and contributes to the voltage drop.
Which of the following tests is used to measure the insulation resistance of a transformer?
A Load test
B Open-circuit test
C Short-circuit test
D Megger test
The Megger test, or insulation resistance test, is used to measure the resistance of the transformer’s insulation. It ensures the integrity of the insulation, preventing electrical faults that could cause damage to the transformer or its connected circuits.
What is the purpose of harmonics in a transformer?
A To increase efficiency
B To cause voltage distortion and increase losses
C To regulate the voltage
D To reduce power losses
Harmonics are higher-frequency components of a waveform that can cause voltage and current distortion. They increase power losses, heat generation, and can affect the operation of transformers and other electrical equipment if not properly managed.
What is the purpose of parallel operation of transformers?
A To share the load
B To improve voltage regulation
C To reduce harmonic distortion
D To convert AC to DC
Parallel operation of transformers allows multiple transformers to share the load, improving overall system reliability and capacity. It is used when more power is required than one transformer can supply.
What is the role of an earthing transformer?
A To step up voltage
B To provide a neutral point for grounding in ungrounded systems
C To reduce harmonic distortion
D To isolate circuits
An earthing transformer provides a neutral point in systems that lack one, such as in delta-connected systems. This neutral point allows for safe grounding, reducing the risk of electrical shock or damage.
Which of the following is a common fault in transformers?
A Overload
B High voltage regulation
C Low core losses
D High efficiency
Common faults in transformers include overloads, short circuits, and insulation breakdowns. These faults can damage the transformer and lead to failure if not properly protected.
What is the purpose of insulation testing in transformers?
A To measure voltage regulation
B To check the condition of the transformer’s insulation system
C To calculate power losses
D To measure the current rating
Insulation testing measures the resistance of the transformer’s insulation system. Proper insulation is crucial for safe operation and to avoid electrical faults.
What is the primary cause of energy loss in a transformer?
A Copper loss and core loss
B Voltage fluctuations
C Harmonics in the system
D Magnetic field interference
Copper losses are due to the resistance of the windings, while core losses occur due to hysteresis and eddy currents in the transformer core. These losses reduce the efficiency of the transformer.
Which of the following is a primary function of a power transformer?
A To step up or step down high-voltage transmission voltages
B To regulate the output voltage in a small system
C To reduce energy loss in the system
D To supply power to the load directly
Power transformers are designed to step up or step down high-voltage transmission voltages. They play a crucial role in transmitting electricity over long distances with minimal losses.