The synchronous generator is an essential component of power generation systems. A synchronous generator is an electrical machine that produces an alternating current (AC electrical current from mechanical energy). It operates on the principle of electromagnetic induction, where a rotating magnetic field is used to induce a current in the stator winding. Given below are the top 10+ MCQ Questions with brief explanatory answers on Electrical Engineering.
In this post Electrical Engineering Online shares Objective Electrical MCQ Questions on Synchronous Generator.
Which of the subsequent is NOT part of a synchronous generator
Which of the subsequent is NOT part of a synchronous generator
- Stator
- Rotor
- Commutator
- Exciter
Correct answer: 3. Commutator
Explanation: A synchronous generator does not have a commutator. Instead, it contains a rotor and a stator. The rotor is the rotating part of the generator, while the stator is the stationary part. The exciter in the alternator provides the necessary field current to the rotor to generate a magnetic field.
The primary operation of a synchronous generator is to
The primary operation of a synchronous generator is to
- Convert mechanical energy into electrical energy
- Convert electrical energy into mechanical energy
- Step up voltage levels
- Store electrical energy
Correct answer: 1. Convert mechanical energy into electrical energy
Explanation: The primary role of a synchronous generator is to convert mechanical energy, usually provided by a prime mover such as a turbine or an engine, into electrical energy. It achieves this by using the rotating magnetic field the rotor generates to induce a voltage in the stator windings.
Which of the below-mentioned quantity decides the frequency of the output voltage of a synchronous generator
Which of the below-mentioned quantity decides the frequency of the output voltage of a synchronous generator
- Rotor speed
- Excitation voltage
- Number of stator windings
- None of above
Correct answer: 1. Rotor speed
Explanation: The frequency of the output voltage of a synchronous generator is directly proportional to the rotor speed. The equation gives the relationship: Frequency = (Number of poles * Rotor speed. / 120. The other options, such as excitation voltage and several stator windings, do not directly determine the frequency.
The term “power factor” refers to
The term “power factor” refers to:
- The ratio of real power to apparent power
- The ratio of real power to reactive power
- The ratio of apparent power to reactive power
- The ratio of real power to voltage
Correct answer: 1. The ratio of real power to apparent power
Explanation: The power factor is the ratio of real power (measured in watts) to apparent power (measured in volt-amperes).
The excitation system of a synchronous generator is responsible for
The excitation system of a synchronous generator is responsible for
- Controlling the generator’s output voltage
- Controlling the generator’s output frequency
- Converting mechanical energy into electrical energy
- Cooling the generator’s windings
Correct answer: 1. Controlling the generator’s output voltage
Explanation: The excitation system of a synchronous generator is responsible for controlling the generator’s output voltage. It regulates the amount of field current supplied to the rotor, which determines the strength of the magnetic field and, consequently, the output voltage. The prime mover typically manages the frequency control, not the excitation system.
The term “synchronization” in synchronous generators refers to
The term “synchronization” in synchronous generators refers to:
- Aligning the rotor magnetic field with the stator magnetic field
- Starting the generator from the rest
- Adjusting the excitation voltage
- Controlling the generator’s output voltage
Correct answer: 1. Aligning the rotor magnetic field with the stator magnetic field
Explanation: Synchronizing a synchronous generator involves adjusting the rotor speed and excitation to match the system frequency and voltage level. This process ensures that the rotor magnetic field is synchronized or aligned with the stator magnetic field, allowing the generator to deliver power to the grid.
The damping winding in a synchronous generator is used to
The damping winding in a synchronous generator is used to:
- Reduce armature reaction
- Improve the power factor
- Control the generator’s speed
- Improve voltage regulation
Correct answer: 1. Reduce armature reaction
Explanation: The damping winding, also known as the amortisseur winding, is placed on the pole faces of a synchronous generator. Its primary function is to reduce the adverse effects of armature reaction, which can lead to voltage drops and other issues. The damping winding provides a path for the flux produced by the armature reaction, mitigating its impact.
The term “slip” in synchronous generators refers to the
The term “slip” in synchronous generators refers to the:
- Difference between the synchronous speed and rotor speed
- Difference between the stator frequency and rotor frequency
- Difference between the excitation voltage and output voltage
- Difference between the rated power and actual power output
Correct answer: 1. Difference between the synchronous speed and rotor speed
Explanation: Slip in synchronous generators refers to the difference between the rotating magnetic field’s synchronous speed and the rotor’s actual speed. Slip is typically expressed as a percentage and indicates the deviation from perfect synchronization. In synchronous generators, the slip is ideally zero.
The function of the damper bars or amortisseur windings in a synchronous generator is to
The function of the damper bars or amortisseur windings in a synchronous generator is to:
- Synchronize the generator with the grid
- Improve the power factor of the generator
- Reduce rotor vibrations and oscillations
- Control the output voltage of the generator
Correct answer: 3. Reduce rotor vibrations and oscillations
Explanation: Damper bars or amortisseur windings are typically in salient-pole synchronous generators. They help dampen or reduce rotor vibrations and oscillations caused by sudden load changes or disturbances in the grid. By dissipating energy, the damper bars enhance the stability and performance of the generator.
A synchronous generator operating at unity power factor means that
A synchronous generator operating at unity power factor means that:
- The generator is not producing any real power
- The generator is not producing any reactive power
- The generator delivers maximum real power
- The generator is delivering maximum reactive power
Correct answer: 3. The generator is delivering maximum real power
Explanation: A synchronous generator operating at unity power factor means that it is delivering its maximum real power output. At the unity power factor, the generator’s reactive power output is minimized, operating at its highest efficiency.
The process of “field flashing” in a synchronous generator refers to the following
The process of “field flashing” in a synchronous generator refers to the following:
- Initiating the synchronization process
- Aligning the rotor poles with the stator poles
- Increasing the excitation voltage to build up the field current
- Adjusting the power factor to unity
Correct answer: 3. Increasing the excitation voltage to build up the field current
Explanation: Field flashing increases the excitation voltage in a synchronous generator to build up the field current in the rotor. Field flashing is typically performed when a generator has lost its residual magnetism or during the initial start-up of the generator. This is necessary to establish the magnetic field required for generating voltage in the stator windings.
When the power entirely goes out, it is essential to excite the fields of power system generators
When the power entirely goes out, it is essential to excite the fields of power system generators using battery power to restart the generators before switching back to using generator output power for field excitation. The aforementioned statement refers to
- Black start
- Redstart
- White start
- None of above
Correct answer: 1. Black start
The purpose of a brushless excitation system in a synchronous generator is to
The purpose of a brushless excitation system in a synchronous generator is to:
- Eliminate the need for slip rings and brushes
- Increase the generator’s speed of operation
- Improve the cooling of the rotor windings
- Reduce the armature reaction
Correct answer: 1. Eliminate the need for slip rings and brushes
Explanation: A brushless excitation system is designed to eliminate the use of slip rings and brushes, traditionally used to supply the field current to the rotor of a synchronous generator. Instead, brushless excitation systems utilize solid-state components, such as diodes and thyristors, to control the excitation current, providing a more reliable and maintenance-free solution.
The term ‘stability of a synchronous generator’ refers to its ability to
The term ‘stability of a synchronous generator’ refers to its ability to:
- Maintain a constant power factor
- Maintain a constant output voltage
- Withstand high electrical loads
- Adjust the rotor speed quickly
Correct answer: 2. Maintain a constant output voltage
Explanation: The stability of a synchronous generator refers to its ability to maintain a constant output voltage despite fluctuations in the load or disturbances in the power system. Stable operation is crucial for maintaining grid stability
The term “infinite bus” in the context of synchronous generators best described as
The term “infinite bus” in the context of synchronous generators best described as
- A power system with a large number of generators
- A power system with an unlimited supply of reactive power
- A power system with a constant voltage source
- A power system with a single generator
Correct answer: 3. A power system with a constant voltage source
Explanation: An infinite bus is a theoretical concept used in power system analysis. It represents a power system with a constant voltage source with an infinite capacity to supply or absorb power and reactive power. The endless bus assumption simplifies the analysis of synchronous generators by assuming a stable and constant voltage reference.
The cooling system of a synchronous generator is primarily responsible for
The cooling system of a synchronous generator is primarily responsible for
- Cooling the stator windings
- Cooling the rotor windings
- Cooling the bearings and shaft
- Cooling the excitation system
Correct answer: 1. Cooling the stator windings
Explanation: The cooling system in a synchronous generator is primarily responsible for cooling the stator windings. Stator windings are often subjected to significant heat due to power losses, and efficient cooling is necessary to maintain their insulation integrity and prevent overheating. Cooling the rotor windings, bearings, shaft, and excitation system may also be part of the overall cooling system design.
A synchronous generator operating with a lagging power factor implies that the
A synchronous generator operating with a lagging power factor implies that the:
- Reactive power is leading the real power
- Reactive power is lagging the real power
- Real power is leading the reactive power
- Real power is lagging the reactive power
Correct answer: 2. Reactive power is lagging the real power