A step-down transformer reduces the voltage from a higher level to a lower level. It has more turns in the primary winding than in the secondary winding, which causes the voltage to decrease while maintaining the current capacity.
What is the main function of an autotransformer?
A To convert AC to DC
B To share a common winding between primary and secondary circuits
C To isolate circuits
D To provide electrical protection
An autotransformer uses a single winding that acts as both the primary and secondary. This makes it more efficient than a conventional transformer for voltage regulation because the voltage transformation happens using part of the same winding.
Which type of transformer is most commonly used for residential applications?
A Power transformer
B Distribution transformer
C Isolation transformer
D Autotransformer
Distribution transformers are used to step down the voltage from high transmission levels to lower levels suitable for residential and commercial use. They are found in power distribution systems.
What is the main characteristic of dry-type transformers?
A They use oil as a coolant
B They do not use liquid for cooling
C They are designed for high-voltage applications only
D They require external cooling
Dry-type transformers use air for cooling instead of oil. They are typically used in environments where safety is a concern, such as in indoor settings, and are more environmentally friendly compared to oil-filled transformers.
What is the primary use of an oil-filled transformer?
A To store electrical energy
B To provide insulation and cooling
C To step up voltage
D To step down voltage
Oil-filled transformers use oil both as an insulator and as a coolant. The oil prevents electrical arcing between windings and also helps to dissipate heat generated during operation, keeping it at a safe temperature.
What is inrush current in a transformer?
A The current that flows through the secondary winding under load
B The surge of current when the transformer is first energized
C The current required to maintain the magnetic field
D The current used to heat the core
Inrush current is a brief surge of high current that occurs when a transformer is first connected to the electrical supply. This surge can be many times higher than the normal operating current, and it is typically caused by the core magnetization process.
What is the purpose of a transformer’s core?
A To increase voltage
B To guide the magnetic flux
C To insulate the windings
D To store electrical energy
The core of a transformer serves as a path for the magnetic flux generated by the primary winding. The core enhances the efficiency of electromagnetic induction between the windings and reduces energy losses.
What type of transformer is used to isolate electrical circuits from each other?
A Step-up transformer
B Isolation transformer
C Distribution transformer
D Autotransformer
An isolation transformer is designed to electrically isolate the primary circuit from the secondary circuit. It provides safety by preventing direct electrical connection between circuits, protecting sensitive equipment from power spikes and faults.
What does the “magnetizing current” in a transformer refer to?
A The current required to power the load
B The current required to magnetize the core of the transformer
C The current flowing in the secondary winding
D The current caused by an overload
Magnetizing current is the small current drawn by the primary winding of a transformer when it is under no load. This current is required to establish the magnetic flux in the core, which is essential for the operation of the transformer.
Which test is used to measure the core loss in a transformer?
A Short-circuit test
B Open-circuit test
C Load test
D Impedance test
The open-circuit test is used to measure the core losses of a transformer. In this test, the secondary winding is open, and the primary winding is supplied with the rated voltage, measuring the losses due to the magnetic properties of the core.
What is the purpose of a transformer’s core?
A To increase voltage
B To guide the magnetic flux
C To insulate the windings
D To store electrical energy
The core of a transformer serves as a path for the magnetic flux generated by the primary winding. The core enhances the efficiency of electromagnetic induction between the windings and reduces energy losses.
What type of transformer is used to isolate electrical circuits from each other?
A Step-up transformer
B Isolation transformer
C Distribution transformer
D Autotransformer
An isolation transformer is designed to electrically isolate the primary circuit from the secondary circuit. It provides safety by preventing direct electrical connection between circuits, protecting sensitive equipment from power spikes and faults.
What does the “magnetizing current” in a transformer refer to?
A The current required to power the load
B The current required to magnetize the core of the transformer
C The current flowing in the secondary winding
D The current caused by an overload
Magnetizing current is the small current drawn by the primary winding of a transformer when it is under no load. This current is required to establish the magnetic flux in the core, which is essential for the operation of the transformer.
Which test is used to measure the core loss in a transformer?
A Short-circuit test
B Open-circuit test
C Load test
D Impedance test
The open-circuit test is used to measure the core losses of a transformer. In this test, the secondary winding is open, and the primary winding is supplied with the rated voltage, measuring the losses due to the magnetic properties of the core.
What is the purpose of a transformer’s core?
A To increase voltage
B To guide the magnetic flux
C To insulate the windings
D To store electrical energy
The core of a transformer serves as a path for the magnetic flux generated by the primary winding. The core enhances the efficiency of electromagnetic induction between the windings and reduces energy losses.
What type of transformer is used to isolate electrical circuits from each other?
A Step-up transformer
B Isolation transformer
C Distribution transformer
D Autotransformer
An isolation transformer is designed to electrically isolate the primary circuit from the secondary circuit. It provides safety by preventing direct electrical connection between circuits, protecting sensitive equipment from power spikes and faults.
What does the “magnetizing current” in a transformer refer to?
A The current required to power the load
B The current required to magnetize the core of the transformer
C The current flowing in the secondary winding
D The current caused by an overload
Magnetizing current is the small current drawn by the primary winding of a transformer when it is under no load. This current is required to establish the magnetic flux in the core, which is essential for the operation of the transformer.
Which test is used to measure the core loss in a transformer?
A Short-circuit test
B Open-circuit test
C Load test
D Impedance test
The open-circuit test is used to measure the core losses of a transformer. In this test, the secondary winding is open, and the primary winding is supplied with the rated voltage, measuring the losses due to the magnetic properties of the core.
What is the main advantage of using dry-type transformers?
A Higher voltage ratings
B Reduced fire risk
C Better cooling performance
D Higher efficiency
Dry-type transformers do not use oil or other flammable liquids, making them safer to use in fire-sensitive environments. They rely on air cooling, which reduces the risk of fire caused by leaks or accidents.
What is the most common method of cooling used in large transformers?
A Air cooling
B Oil cooling
C Liquid nitrogen cooling
D Water cooling
Oil cooling is the most common method used for large transformers. The oil serves both as an insulator and a coolant, removing heat generated by the transformer and preventing overheating.