1. What is Inrush Current ?
Ans. The starting current of any electrically operated equipment such as motors generators etc. is known as inrush current.
2. What is main difference between current and voltage ?
Ans. Current is the movement of electrons whereas Voltage is the driving force which is causing the movement of electrons due to potential difference between two points.
3. Why the supply frequency is selected as 50Hz in Pakistan or 60Hz in Western countries ?
Ans. There is no hard and fast rule for selecting this number. On the basis of this frequency every electrical equipment is designed if one wants to change this. Every electrical operated equipment running at AC current have to be changed.
4. What is the purpose of coupling capacitor ?
Ans. It just removes the ripples in the AC current.
5. What is the difference between Earthing and Grounding ?
Ans. Earthing is used when metallic equipment is used for providing low resistance path to the current. Grounding is the return path for the current current flows in it in normal conditions and current flows in earthing wire during fault condition.
6. Where is tap changer connected in the tap changing transformers ?
Ans. Tap changer is connected in the high voltage winding because current in the high voltage is less and while changing the taps less or no spikes will be generated thus winding will not burn.
7. How many types of losses in transformers ?
Ans Two types of losses in transformers
Iron losses
Copper losses
8. Why the transformers are rated in KVA ?
Ans. T's are rated in KVA because losses in transformers are dependent on current (copper losses) and voltage (Iron losses) and not the angle between them or the power factor hence T's are rated in kVA not in kW. KVA does not include the power factor but kW does include.
