Electronics and Electrical Engineering interview Question and Answers for fresh engineers (Part 7)

Electronics and Electrical Engineering interview Question and Answers for fresh engineers (Part 7)

In this topic we know about the Power Factor, the leading and lagging condition for the power factor, the disadvantage of the low Power Factor and the main causes of the low power factor.

 Question: What is Power Factor?

 Answer: In an a.c. circuit the cosine of angle between voltage and current is called as power factor.

Fig: Power factor angles

 Question: What are the leading and lagging conditions in the power factor improvement?

 Answer: Normally there are two types of circuit, capacitive and inductive circuits.

·        In the capacitive circuits, current leads the voltage and power factor is called as leading.

·        In the inductive circuits, current lags behinds the voltage and power factor is called as lagging.

Question: What are the disadvantages of low power factor?

 Answer: The main disadvantages of low power factor are as follows,

1.     Large size of the Conductor.

2.     Large Kilo Volt Ampere rating of the electrical machinery or equipment.

3.     Poor or unaccepted voltage regulations.

4.     A big amount of Copper loss.

5.     The handling capacity of the system reduced.

Question: What are the main causes of the low power factor?

 Answer: In the supply system normally the power factor is lower then 0.8 for the overall load. Low Power factor is very undesirable, because it hampers the economic parameters for the power generation and distribution. Now, some short important causes are as follows,

·        In the low lagging factor some electrical equipment such as electric discharge lamps, Arc lamps and the industrial heating furnaces are running.

·        The power factor is also depending on the load conditions. The load is varying time to time.  The supply voltage is increasing in the low load period which increases the amount of the magnetization current. This magnetizing current is resulting in the decreased power factor.

·        The single phase and three phase ac motors have low lagging power factor and they are induction type also. The power factor is varying for these types of motor. It can run from 0.2 to 0.9 values depends on load. In the heavy load the power factor can be 0.8 or 0.9 and in the light load the power factor can be 0.2 to 0.3.

-- - - - -- --- - -- - - -- - - - -- -  -- - - - - -  -- - - - -- - - - - - - - - 

We will give more important questions and answers for electrical engineering interview very soon. Please subscribed to RSS feed or Email feed. We need your help for the betterment of the site. Please give comments and tell us what’s your opinions and needs from us. We will try to give your required things.

Electrical engineering interview