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
📅 Oct 2025
Reference Answer
### (a) Purpose of the Automatic Voltage Regulator (AVR)
The primary purpose of an Automatic Voltage Regulator (AVR) in a shipboard alternator is to maintain a constant terminal output voltage under varying load conditions. It forms the core of the alternator's closed-loop control system for voltage regulation.
**Key Functions and Importance (Surveyor-Grade Detail):**
1. **Voltage Regulation:** The AVR continuously senses the alternator's output terminal voltage and compares it to a stable internal reference voltage (typically generated by a Zener diode). If a deviation (error signal) is detected due to a change in load, the AVR automatically adjusts the excitation current to correct the voltage back to its pre-set value (e.g., 440V).
The primary purpose of an Automatic Voltage Regulator (AVR) in a shipboard alternator is to maintain a constant terminal output voltage under varying load conditions. It forms the core of the alternator's closed-loop control system for voltage regulation.
**Key Functions and Importance (Surveyor-Grade Detail):**
1. **Voltage Regulation:** The AVR continuously senses the alternator's output terminal voltage and compares it to a stable internal reference voltage (typically generated by a Zener diode). If a deviation (error signal) is detected due to a change in load, the AVR automatically adjusts the excitation current to correct the voltage back to its pre-set value (e.g., 440V).
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