Welcome to Electrical Engineering XYZ MCQs post on synchronous generators. If you’re looking to test your knowledge or gain a deeper understanding of synchronous generators, you’ve come to the right place. Synchronous generators, also known as alternators, play a crucial role in converting mechanical energy into AC electrical energy. In this post, we’ve curated a collection of multiple-choice questions (MCQs) that will challenge your understanding of synchronous generator principles, operation, and key concepts. Whether you’re a student, an engineer, or simply interested in the topic, these MCQs will help you assess your grasp on synchronous generator fundamentals. Get ready to dive into the world of synchronous generators and expand your knowledge through this engaging MCQ post on Synchronous Generators.
Contents
- 1 Synchronous Generator is also known as
- 2 The stator of an alternator rarely employs
- 3 A turbo-alternator uses
- 4 The synchronous reactance of alternator is due to
- 5 The voltage regulation of an alternator for PF of 0.8 lagging is X at unity PF
- 6 The magnitude of EMF generated by an alternator depends on
- 7 When the alternator operates at a unity load power factor the effect of armature reaction is
- 8 The frequency of EMF generated per revolution in an alternator is equal to
- 9 The stator of an alternator is wound for ____________ on the rotor
- 10 Voltage regulation of an alternator is larger than that of a DC generator because of
Synchronous Generator is also known as
Synchronous Generator is also known as:
- Alternator
- DC Generator
- Both of these
- None of these
Correct answer: 1. Alternator
Explanation: An alternator is a type of synchronous generator that converts mechanical energy into electrical energy. It is commonly used in power plants, automotive applications, and other industries to generate alternating current (AC). The term “alternator” is often used interchangeably with “synchronous generator” because both refer to the same device.
On the other hand, a DC generator, also known as a dynamo, is a different type of generator that produces direct current (DC). Unlike an alternator, which generates AC, a DC generator uses a commutator and brushes to convert mechanical energy into DC.
Therefore, when considering the given options, the correct choice is “Alternator.”
The stator of an alternator rarely employs
The stator of an alternator rarely employs
- Closed type slots
- Wide open type slots
- Semi-closed type slots
- None of these
Correct answer: 1. Closed type slots
A turbo-alternator uses
A turbo-alternator uses:
- Rotating AC armature winding
- Salient-pole field structure
- Non-salient-pole field structure
- None of the above
Correct answer: 3. Non-salient-pole field structure
Explanation: Turbo alternators are high speed alternators that posses non-salient rotors. This is done primarily because of two reasons.
- At high speeds salient pole rotors have large windage losses
- It is quite hard to build salient pole construction, since at high speeds they can’t withstand centrifugal speeds
The synchronous reactance of alternator is due to
The synchronous reactance of alternator is due to:
- Armature reaction
- DC Field excitation
- Leakage flux
- None of the above
Correct answer: 1. Armature reaction
Explanation: The synchronous reactance of an alternator is primarily influenced by armature reaction. Armature reaction refers to the magnetic field produced by the flow of alternating current in the stator windings of the alternator. This current produces a magnetic field that interacts with the rotor’s magnetic field, resulting in the distortion of the magnetic field in the air gap.
The interaction between the rotor’s magnetic field and the distorted stator magnetic field causes a phenomenon called armature reaction, which affects the synchronous reactance. Synchronous reactance represents the opposition offered by the alternator’s windings to the flow of alternating current and is an essential parameter in analyzing the performance of synchronous machines like alternators.
The other options listed in the question are not directly responsible for the synchronous reactance:
- DC field excitation: While the field excitation current is necessary for establishing the rotor’s magnetic field, it does not directly contribute to the synchronous reactance. The field excitation current primarily influences the strength and shape of the rotor magnetic field, which, in turn, affects the alternator’s voltage output and reactive power capability.
- Leakage flux: Leakage flux refers to the magnetic flux that does not link with the windings of the alternator. Although leakage flux can have an impact on various aspects of alternator performance, it does not directly contribute to the synchronous reactance. Leakage flux affects parameters such as voltage regulation, losses, and overall efficiency of the alternator.
Therefore, the correct answer to the given multiple-choice question is “Armature reaction.” The synchronous reactance of an alternator is primarily influenced by the effects of armature reaction, while the other options listed (DC field excitation and leakage flux) are not directly responsible for determining the synchronous reactance.
The voltage regulation of an alternator for PF of 0.8 lagging is X at unity PF
The voltage regulation of an alternator for PF of 0.8 lagging is X at unity PF. Here X implies
- Smaller than
- Greater than
- The same as
- None of the above
Correct answer: 2. Greater than
Explanation: The voltage regulation of an alternator refers to the change in voltage between no load and full load conditions. It is typically expressed as a percentage and is calculated by subtracting the no-load voltage from the full-load voltage, divided by the no-load voltage and multiplied by 100.
In the given question, it states that the voltage regulation of the alternator is X at unity power factor (PF). Unity power factor means that the load on the alternator is purely resistive, resulting in a power factor of 1.
Since the power factor is given as 0.8 lagging for which the voltage regulation is X, and unity power factor (PF = 1) is resistive, the voltage regulation at unity power factor will be greater than X. This is because inductive loads (lagging power factor) cause more voltage drop compared to resistive loads (unity power factor). Therefore, the voltage regulation at unity power factor will be higher or greater than the voltage regulation at a power factor of 0.8 lagging.
The magnitude of EMF generated by an alternator depends on
The magnitude of EMF generated by an alternator depends on:
- Rotor speed
- Flux per pole
- Number of poles
- All of these
Correct answer: 4. All of these
When the alternator operates at a unity load power factor the effect of armature reaction is
When the alternator operates at a unity load power factor the effect of armature reaction is:
- Wholly distorting
- Wholly demagnetizing
- Wholly magnetizing
- Partly distorting, partly demagnetizing
Correct answer: 1. Wholly distorting
The frequency of EMF generated per revolution in an alternator is equal to
The frequency of EMF generated per revolution in an alternator is equal to:
- Number of poles
- Number of pair of poles
- Twice the number of poles
- Thrice the number of poles
Correct answer: 2. Number of pair of poles
Explanation: An alternator consists of a rotating rotor and a stationary stator. The rotor is equipped with electromagnets or permanent magnets, which create a rotating magnetic field as the rotor spins. The stator, on the other hand, contains a set of conductive windings or coils.
When the magnetic field of the rotor cuts across the stator windings, an alternating current (AC) is induced in the stator coils. The frequency of this alternating current corresponds to the rate at which the magnetic field is changing or rotating.
The frequency of the induced EMF is directly related to the speed of the rotor and the number of magnetic poles. It is given by the formula:
Frequency = (Number of poles × Speed in revolutions per second) / 120
However, it’s important to note that the number of poles mentioned in the formula refers to the number of pairs of poles rather than the actual count of individual poles. In an alternator, each pole consists of a north pole and a south pole. Therefore, the number of pairs of poles is equal to the number of individual poles divided by 2.
So, to calculate the frequency of the generated EMF per revolution, we use the formula:
Frequency = (Number of pairs of poles × Speed in revolutions per second) / 120
Based on this explanation, the correct answer to the multiple-choice question would be “Number of pair of poles.” The frequency of the EMF generated per revolution in an alternator is equal to the number of pairs of poles.
The stator of an alternator is wound for ____________ on the rotor
The stator of an alternator is wound for ____________ on the rotor:
- The same number of poles as
- More number of poles than
- Less number of poles than
- None of the above
Correct answer: 1. The same number of poles as
Voltage regulation of an alternator is larger than that of a DC generator because of
Voltage regulation of an alternator is larger than that of a DC generator because of
- Large leakage reactance
- Large armature resistance
- Complex effects of armature reaction
- None of these
Correct answer: 3. Complex effects of armature reaction
More MCQs on Synchronous Generators
- Synchronous Generator MCQs Part 1
- Synchronous Generator MCQs Part 2
- Synchronous Generator MCQs Part 3
- Synchronous Generator MCQs Part 4
- Synchronous Generator MCQs Part 5
- Synchronous Generator MCQs Part 6
- Synchronous Generator MCQs Part 7
- Synchronous Generator MCQs Part 8
- Synchronous Generator MCQs Part 9
- Synchronous Generator MCQs Part 10
- Synchronous Generator MCQs Part 11
- Synchronous Generator MCQs Part 12
- Synchronous Generator MCQs Part 13
- Synchronous Generator MCQs Part 14
- Synchronous Generator MCQs Part 15