Class 4 (4th Engineer) MET 📅 Aug 2022

Exam Question

(a) Describe the basic principles a self-excited generator. (6)

(b) The armature resistance of a 200 V, Shunt motor is 0.4 ohms and the no-load armature current is 2A. When fully loaded and taking an armature current of 50 A, the speed is 1200 rev/min. Find the no-load speed and state the assumption made in the calculation.

Reference Answer

### (a) Basic Principles of a Self-Excited Generator (6 Marks)
#### 1. Fundamental Principle
A self-excited generator is a DC machine that utilizes its own output voltage to energize its field winding, thereby creating the magnetic field necessary for electricity generation. This is in contrast to a separately-excited generator, which requires an external DC power source for its field winding.
The operation relies on the phenomenon of **residual magnetism** within the iron cores of the field poles.

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