What determines the synchronous speed of an alternator?
A Rotor Speed
B Number of Poles
C Voltage Output
D Frequency
The synchronous speed of an alternator is determined by the formula: 120 × frequency / number of poles. The rotor must rotate at this speed to produce alternating current at the correct frequency.
What happens when the slip in an induction generator increases?
A Increases Efficiency
B Increases Frequency
C Decreases Power Output
D Decreases Voltage
As slip increases in an induction generator, the rotor speed decreases relative to synchronous speed. This leads to a drop in the generated voltage, reducing the efficiency and power output of the generator.
What is the relationship between synchronous speed and frequency in an alternator?
A Directly Proportional
B Inversely Proportional
C Unrelated
D Dependent on Load
The synchronous speed of an alternator is directly proportional to the frequency of the system. As frequency increases, synchronous speed increases, ensuring the rotor rotates in sync with the power grid.
How does the slip in an induction motor affect its performance?
A Increases Torque
B Increases Power Output
C Reduces Efficiency
D Increases Speed
Slip represents the difference between the synchronous speed and the actual speed of the rotor. Higher slip leads to increased losses, reducing the overall efficiency of the induction motor.
What is the main feature of a self-excited induction generator?
A Requires External Power
B Does Not Require External Excitation
C Works at Fixed Speed
D Generates DC Power
A self-excited induction generator generates its own excitation by using capacitor banks. It does not need an external source of excitation like synchronous generators, which makes it more flexible for applications like wind energy generation.
What causes an induction generator to operate at variable speeds?
A Wind Speed
B Load Variations
C Excitation Changes
D Rotor Design
Induction generators are commonly used in wind power generation, where the speed of the rotor changes depending on wind speed. This ability to adapt to varying speeds makes them ideal for renewable energy applications.
How is the slip in an induction generator calculated?
A Rotor Speed / Synchronous Speed
B (Rotor Speed + Synchronous Speed) / Synchronous Speed
C (Synchronous Speed – Rotor Speed) / Synchronous Speed
D (Frequency × Poles) / Rotor Speed
Slip in an induction generator is calculated as the difference between synchronous speed and rotor speed, divided by synchronous speed. Slip indicates the extent of the difference in speed required for generating electrical power.
Which of the following is characteristic of a doubly-fed induction generator (DFIG)?
A Operates at Fixed Speed
B Uses External Excitation
C Does Not Require Capacitors
D Provides Variable-Speed Operation
A doubly-fed induction generator (DFIG) can operate at variable speeds, making it suitable for wind power generation. It allows for better efficiency and adapts to changing wind conditions by adjusting the rotor speed.
What type of generator is most commonly used in wind power applications?
A Induction Generator
B Synchronous Generator
C Permanent Magnet Generator
D Self-Excited Generator
Induction generators, particularly squirrel-cage types, are commonly used in wind power applications because they can operate at variable speeds and do not require external excitation, making them ideal for fluctuating wind conditions.
In an induction generator, what causes the frequency of the generated power to remain constant?
A Rotor Speed
B Excitation System
C Grid Synchronization
D External Power Source
In an induction generator, the generated frequency is synchronized with the grid frequency. Even though the rotor speed may vary, the alternator adjusts to match the grid’s frequency, ensuring stable power output.
What is the significance of the slip in an induction generator?
A Determines Voltage
B Controls Efficiency
C Controls Frequency
D Indicates Rotor Speed
Slip in an induction generator influences efficiency. When slip is too high, the generator becomes less efficient, as it consumes more energy to maintain the necessary power output. Low slip is desired for better efficiency.
How does the rotor of an induction generator generate electrical power?
A By Producing a Magnetic Field
B By Rotating at Synchronous Speed
C By Inducing Current in the Stator
D By Creating a Rotating Magnetic Field
In an induction generator, the rotating rotor induces current in the stator windings through electromagnetic induction. The relative motion between the rotor and stator creates an electrical current that is then outputted as AC power.
What is a major advantage of a permanent magnet generator over an induction generator?
A Higher Efficiency
B Variable Speed Operation
C Simplicity of Design
D No External Excitation
Permanent magnet generators are more efficient than induction generators because they do not rely on external excitation. The permanent magnets provide the necessary magnetic field for power generation, reducing energy losses and improving overall efficiency.
How does an induction generator respond to a drop in load?
A Increases Speed
B Stops Operation
C Reduces Power Output
D Increases Voltage
When the load on an induction generator decreases, it reduces the power output. Induction generators automatically adjust to variations in load, decreasing their power generation to match the demand, thus ensuring efficiency.
What does the term “synchronous speed” refer to in an induction generator?
A Speed at Which the Stator Rotates
B Speed Corresponding to Grid Frequency
C Speed at Which the Rotor Rotates
D Speed of Rotor and Stator Together
Synchronous speed refers to the speed at which the magnetic field in the stator rotates, corresponding to the grid frequency. The rotor must rotate at or near this speed for optimal power generation in an induction generator.