Exam Question
(a) What is the purpose of AVR in an alternator? (6)
(b) With the aid of a simple circuit diagram explain the basic working of a brushless alternator. (10)
Class 4 (4th Engineer)
MET
📅 Nov 2023
Reference Answer
### (a) Purpose of AVR in an Alternator (6 Marks)
The Automatic Voltage Regulator (AVR) in an alternator is a crucial component designed to maintain a stable and constant output voltage under varying load conditions, excitation changes, and rotational speed fluctuations. Its primary purposes are:
* **Voltage Stability**: The most fundamental purpose is to maintain the alternator's output terminal voltage within a specified narrow tolerance range (typically ±0.5% to ±1.0% of the nominal voltage). This ensures a consistent power supply to all connected consumers.
* **Load Compensation**: As the electrical load on an alternator changes (e.g., motors starting, heaters switching on/off), the terminal voltage tends to drop due to internal impedance voltage drops. The AVR senses this voltage drop and automatically increases the excitation current to the alternator's field winding, thereby boosting the magnetic field and restoring the voltage to its set point.
The Automatic Voltage Regulator (AVR) in an alternator is a crucial component designed to maintain a stable and constant output voltage under varying load conditions, excitation changes, and rotational speed fluctuations. Its primary purposes are:
* **Voltage Stability**: The most fundamental purpose is to maintain the alternator's output terminal voltage within a specified narrow tolerance range (typically ±0.5% to ±1.0% of the nominal voltage). This ensures a consistent power supply to all connected consumers.
* **Load Compensation**: As the electrical load on an alternator changes (e.g., motors starting, heaters switching on/off), the terminal voltage tends to drop due to internal impedance voltage drops. The AVR senses this voltage drop and automatically increases the excitation current to the alternator's field winding, thereby boosting the magnetic field and restoring the voltage to its set point.
Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.
Prepare on Android — MeoMock on Google Play