Class 4 (4th Engineer) MET 📅 Dec 2022

Exam Question

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

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

Reference Answer

### (a) Improvement of Fluorescent Tube Power Factor
A standard fluorescent lamp circuit inherently exhibits a low, lagging power factor. This is primarily due to the inductive ballast (choke) connected in series with the lamp.
**1. Cause of Low Power Factor:**
* **Inductive Ballast:** The ballast is an inductor (a coil of wire wrapped around an iron core). Its primary function is to provide a high initial voltage to start the arc in the tube and then to limit the current to a safe operating value once the lamp is lit.

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