# Basic Electrical Questions

Basic Introduction Questions

1. What is control system?

Answer: A control system is a system that takes some input and performs some operations on it and gives us the controlled or desired output.

2. What are the different types of control system?

Answer: Control system can be of many types depending on the type of input and output.Some basic types of Control Systems are:

Linear Control System, Non-linear Control System, Analog Control Systems, Digital Control Systems, SISO Control Systems, MIMO Control Systems.

3. What is a Latching current?

Answer: It is the minimum current required by an SCR in forward Bias to remain in Forward Conduction Mode.

4. Why thyristor is considered as charged controlled device?

Answer:  It  is because SCR is Triggered using GATE Pulses and Larger the Pulse magnitude i.e larger the charge injection through gate, the faster is the triggering of SCR. Thus, it is called as Charge Controlled Device.

5. What are the different losses that occur in thyristor while operating?

Answer: Different losses that occur in a thyristor during operation are:

Forward Conduction losses, Leakage Current Loss, Gate Triggering Loss and Switching Losses.

6. What is the reverse power relay?

Answer: It is a special type of relay that prevents the flow of power in reverse direction or we can say allows the power to flow only in the forward direction.

7. What is meant by knee point voltage?

Answer: Knee Point voltage is basically that voltage level after which even  a small change or increase in voltage level results in a very high change or increase in the Magnetizing Current.

8. What will happen if DC voltage is given on the primary of a transformer?

Answer: If DC is given to the primary of the transformer due to its inductive coils it will show very little resistance to the DC Current and a huge current will be there in secondary thus resulting in the burning of the coils.

9. Why the capacitor works on ac only?

Answer: Because in case of the DC due to its frequency the resistance offered by the capacitor is very high thus it blocks the DC voltage completely once fully charged.

10. Why delta star transformers are used for lighting loads?

Answer: Because in lighting loads we need a neutral to feed from each phase which is only possible in Delta -Star Formation.

11. What is Electrical Engineering?

Answer: Electrical engineering is that field of engineering which deals with the development of electrical power, its distribution and its regulation etc.

12. What is ideal transformer?

Answer: Ideal Transformer is a hypothetical concept in which a lossless  and 100% efficient transformer is called as Ideal Transformer.

13. What are transformer losses and their types?

Answer: Most basic type of transformer losses are Hysteresis loss, Copper Loss, Iron Loss, Eddy Current Loss, and Dielectric Loss

Transformers are of two types in general. These are:

1. Potential Transformer

2. Current Transformer

14. What is the voltage regulation of the transformer & why is it important?

Answer: Voltage regulation of a transformer simply tells us about the efficiency of a power transformer to maintain constant voltage on Secondary side if the current on primary side varies but voltage is constant.

15. Does current lead or lag the voltage in an inductive or capacitive circuit?

Answer: The current lags the voltage in inductive circuit and leads the voltage in Capacitive circuit.

16. What is the maximum power transfer theorem?

Answer: The maximum power transfer theorem states that in a linear, bilateral DC network , maximum power is transferred to the load when the load resistance is equal to the internal resistance of a source.

17. Why do we improve the power factor?

Answer: We can improve the power factor by using more Capacitive load in network or by using a Capacitor Bank.

18. What is a motor starter?

Answer: Motor Starter is simply a device used to safely start the motor without damaging its windings due to high starting current.

19. What is the difference between circuit breaker & isolator?

Answer: The basic difference is that the circuit breaker is used for switching purpose in a power system when it is in on-load condition while the isolator is used for separating a part of the power system from it when under off load condition.

20. What are the different colors on wires indicates?

Answer: Different colors on the wires indicate there usage for different purpose in wiring etc. For ex: Red is used generally for the Phase and Green for the Ground and Black for he neutral in Indian Standards.

21. Why we use 3-phase supply? Why are not 4 or something else?

Answer: We use a 3-phase supply because it gives balanced supply i.e. having a difference of 120 between each phase and is easy to design than 4 or some other phase systems.

22. What is 2 phase motor?

Answer: These are nothing but simple motors just having 2 windings in such a manner that they have a difference 90 degree electrical between them.

23. What is Automatic Voltage Regulator (AVR)?

Answer: The automatic voltage regulator is used to regulate the voltage. It takes the fluctuating voltage and changes it into a constant voltage. It works on the principle of detection of error from a specified or desired value and regulating according to it.

24. How many types of cooling system it transformer?

Answer: Basic types of cooling in Transformer are :

Air cooling, Oil and Air Cooling, Oil and Water Cooling

25. What is the difference between delta-delta, delta-star transformer?

Answer: Delta - delta transformer is used at Generating station or a receiving station for Change of Voltage, generally it is used where the Voltage is high & Current is low. While Delta star is a distribution kind of transformer wherefrom secondary star neutral is taken as a return path, this configuration is used for Step down voltage phenomena.

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