March 2014|Online electrical engineering & Electrical Interview Questions

Saturday, March 22, 2014


What is wave Trap and uses of wave trap ? Here is the answer to the question from our follower.

Wave trap is a device used in the substation at the incoming lines.Wave trap is also called as line trap.As the name indicates a wave trap, is used to trap/catch the wave.But what is that wave and why it should be trapped/caught by  a wave trap ?

Have you ever heard of Power Line Carrier Communication (PLCC) ? The substations uses the power line for communication purpose also. They use high frequency waves to communicate between the substations. Communication between the substation was done using the power lines in the days where communication through the telephone/communication lines were difficult. But still PLCC is adopted in the substations as it is faster, easier,  cost effective and also very safe to transmit the messages without any interference.

Are you confused, whether it is possible to send 2 waves in a single transmission line ? Yes, it is possible the power signal will be at the frequency of 50 Hz whereas the communication signal's  frequency would be in the range of kHz.

What happens when wave trap is not used at the entrance of substation ? If the communication frequencies are not filtered, then it would act as harmonics to the electrical equipments like transformers, circuit breakers and damage the equipments.

So in order to protect the electrical equipments and for communication purpose the wave trap is used in the substation. I have attended industrial training at a substation and I have seen these wave traps directly and how the maintenance works are done at substation. I would suggest you students also to attend training like this and gain knowledge. I am sure it would be a nice fun and good practical learning experience.

Sunday, March 16, 2014


Hi all.Please take up the Electrical Engineering Test-4.The test contains the questions which were asked in some competitive exams.Some questions are problematic and others are theoretical. Though most of the questions are theoretical it would be helpful in understanding the basic concepts of electrical engineering.We have been preparing questions ourselves, so that it is useful for all Electrical Engineers.Online Electrical Engineering team will be coming up with more tests :) Your valuable comments are welcome to improve the quality of the tests.
Cheers !!

Tuesday, March 4, 2014


Can I plug a 10.7kW cooker into a 13A socket ? is today's electrical engineering question asked by one our followers.Before answering this question let us see some of the basics concepts in Electrical Engineering which would obviously give answer to this question.

What is the voltage used in India for domestic purpose ? the answer to this is 240V with 50Hz frequency. So all the appliances/generators will be manufactured in such a way that it supports the 50hz frequency and the 240V.

What is the voltage used in USA for domestic purpose ? the answer to this question would be 120V with 60 Hz frequency. So the appliances manufactured should be supporting these specifications.

Having sorted out the voltage we use, now let us see how much power/ Current would our appliance draw based on our usage.The question states that the rated power of the cooker is 10.7kW.So let us assume it will work on 240V/50Hz supply.
Power = V* I 
10700 = 240 * I
I = 10700/240 =44. 583 A
So if we want to plug the cooker and use it in a 240V supply it would require a 45A socket or a 50A socket.What would happen if you plug it in a 13A socket ? the answer is simple but not the real outcome of it as the socket would blast because it cannot withstand only 45A drawn by the appliance. 

Have you ever seen the sockets used for the home appliances like TV, Refrigerators, Air conditioners, Geysers ? 
For TV mostly we use 5A socket, for Refrigerators we use 5A - 10A socket based on the capacity of the Refrigerators. For AC we use 20A socket. And for Geysers we use a 25A socket. Again remember that the Ampere rating of the socket may vary with respect to the capacity of the appliance. What are you waiting for ???!! Just jump up from your PC and check the Ampere rating of the socket you use in your home and post it in comment.. Any US visitors also can post you comment in the comments section to enlighten what is practically used in US. Cheers guys !!