Class 4 (4th Engineer) MET 📅 Jun 2025

Exam Question

(a) Explain how fluorescent tubes power factor is improved. (6)

(b) A fluorescent lamp taking 80W at 0.7 power factor lagging from a 230v, 50-Hz supply is to be connected to unity power factor. Determine the value of the correcting approach required. (10)

Reference Answer

### (a) Improvement of Fluorescent Tube Power Factor (6 Marks)
#### 1. The Cause of Low Power Factor
A standard fluorescent lamp requires a high voltage surge to initiate the arc through the gas inside the tube and then a lower, stable voltage to maintain it. To achieve this and to limit the current once the arc is struck, a series inductive ballast (or choke) is used.
* **Inductive Nature:** The ballast is essentially a coil of wire, making it a highly inductive component.

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