EEE_Question-Answers

    1.      How are the power correction capacitors available?

They are sold at a specific voltage rating by kVAR. They are sold in a trio of three capacitors. They are connected to induction motors and switched.

  2.      A star delta starter is used with induction motor. What is the reason behind it and mention its advantages?

The main advantage of using a star delta starter with induction motor is that the less amount of current can be made use of during the starting of the motor. Hence the current spent in total is also reduced.

3.      What is the use of a circuit breaker? Is it same as that of a fuse?

It is different from that of a fuse. It is used to reset the protective device. When heavy loads of input flows in, the fuse cuts of the internal connection and this breaker resets the protective device alerting it for safeguarding the entire unit.

4.      What can be the voltage gain of the voltage follower?

A voltage follower is a device whose output will merely just follow the input and hence won’t have any gain.

  5.      In power systems, what is the prime method that is followed to improve power quality?

A capacitor bank can be connected in series with the load which will result in the improvement of the overall power factor and power supply.

6.      Why are the transformers’ current measures in kVA? 

kVa is basically a unit that is used to measure apparent power which is a combination of active and reactive power. The transformer current generally includes the higher frequencies like the harmonics. Hence kVA is the easy way of measuring this type of current.

7.      What is known as regenerative breaking?

It is a general phenomenon that a motor continues running even after the power is cut off. This is due to the residual inertia. A load resistor is placed in the unit to prevent the motor from running after the power cut. The back e.m.f voltage is applied back across the resistor and due to this load the motor stops running. This entire mechanism is called as regenerative breaking.

  8.      Where is the output of an RC integrator taken across?

RC is a combination of resistor and capacitor. When load is applied across this unit, the output is obtained from the capacitor.

 9.      What is the two terminal voltage variable resistor popularly known as?

It is known as Rheostat.

10.  Why is DC flow of current blocked in a capacitor?

A capacitor’s reactance is inversely proportional to the frequency. For d.c. current there is no frequency and hence the reactance of the capacitor becomes infinite. This is the reason why a capacitor blocks DC.

11.  A humming sound occurs in the HT transmission. Why is that?

Ionization occurs due to the air break down in to the charged particles around the transmission conductors. This is the reason behind the humming sound and it is technically known as corona effect. In lay men terms it is a form of power loss.