Difference Between Neutral Vs Earth wire

   

Neutral:         

•  Neutral is the normal "return" wire.  In systems where the load is supplied from only one Hot (or "Live") wire, the Neutral completes the circuit and carries current back from the load to the power station.  
• Neutral is a conductor that carries current in normal operation.  
• Neutral represents a reference point within an electrical distribution system.  

Earth "Ground"

•  Earth or Ground wire is a safety protective wire for the human body and electrical equipments from fault conditions. 
•  Earth is a conductor that carries no current in normal operation.
• Earth is a conductor that carries current under fault conditions such as insulation breakdown that occurs within electrical equipment.

Why Earth Pin Is Thicker And Bigger In A 3-Pin Plug?

• In Our home appliances, we are having some are two pin - plugs and some are three pin plugs.  If you see in any place around the world, you will find the same concept behind every three pin - plug.  A top pinhole of a socket and top pin of three - pin plug is bigger as well as thicker than the rest of the two pins (Live and Neutral pins).
• In a 3 - pin plug (as shown in the above fig) • The Green and Wire is Earth (IEC & NEC) Brown is Live / Line (Black in US) • Blue is Neutral (White in US) 

1. Why earth pin is bigger? 

•  Earth pin is bigger (longer than live and neutral pins. When the plug is inserted in the socket, cause of longer earth pin first it makes contact to the earth hole prior to live and neutral. Thus earth connection is made before the current - carrying  contacts of the plug become live. When the plug is removing from the socket, Earth pin comes out last. Means earth connection is removed after the current - carrying contacts separate. Due to this, it can protect us from any kind of shocks.

2. Why earth pin is thicker ?(in cross section area)

• First reason, to prevent the wrong way to operate a 3 - pin plug and connected electrical machine for the safety purpose.  In other words, the 3 - Pin plug won't be connected to the socket upside down as the earth pin is thicker, so it won't adjust and fit in another slot made for Neutral or Live Pin in the socket.  In short, the earth pin is bigger and it can not be inserted in the live or neutral slot of the socket even by mistake.
• Second reason,  R= p×L/A     where       • R = Resistance • p = Resistivity.  L = Length of the Conductor.  a = Area of ​​the conductor 
• It clearly shows that the resistance is inversely proportional to the area of ​​the conductor.  i.e.  The thicker of the conductor, the lesser is the resistance.  In this case, when a wet body (Keep in mind that wet body has very low resistance) touches the metallic body of the machine where leakage current exists.  Current will flow through it as it finds the easiest way (having very low resistance) to complete the path.  So there is still a chance of electric shock in the above - mentioned case.
• Third reason, modern 3 pin wall sockets have safety shutter on the Line and Neural lines to prevent someone (especially children) to insert circulating materials in it which causes electric shock.  In this case, the longer earth pin help to open the shutters for Line and Neutral pins i.e, without longer earth pin, The shutters for Line and Neutral remains closed for better safety.

Function of breather in Transformer

• Breather salica gel 

The function of breather in transformer is to filter out the moisture from air. Breather consist of silica gel which absorbs the moisture from air.

When there is overloading on transformer, the winding of transformer gets heated so the oil in main tank of transformer also get heated. The hot oil started expanding. There is conservator tank at the top of transformer which allows adequate space for expansion of oil. Therefore during overloading condition the oil move to the conservator tank.

In normal operating condition, the oil come back to main tank from conservator tank. Now, there is vacant space in the conservator tank which is filled with the air. Conservator tank is never completely filled as it has to allow space for expanding oil from main tank.

The air which is there in conservator tank is coming from atmosphere through the breather and breather contains silica gel in it. This silica gel absorbs the moisture from air. The main reason to remove moisture from air is because the moisture degrades the dielectric strength of the transformer oil.

Basic Electrical Engineering Interview Question Answers

•  what is electrical engineering

Electrical Engineering the field of Engineering that generally deals with the study and application of electricity, electronics, and electromagnetism.Electrical engineering deals with high voltage especially AC above the range of 110 or 220V. Moreover, electrical components and devices use alternating current (AC) / Voltages and tend to be larger in size and require 230V (In UK) and 110V (In US) single-phase ac voltages whereas in industries and power stations, it may be up to 11kV and for transmission, it may be higher than 400kV.

•  what is an ideal transformer

A ideal transformer is an imaginary transformer in which no losses occur at all. In other words, the transformer Input power is equal to the output power of the transformer i.e. they have 100% efficiency. It is just a theoretical transformer because there must be some losses in a real transformer.

Transformer input Power = Transformer Output Power.

PIN = POUT.

• Why Transformer in rated in KVA, not in kilowatt

When manufacturers design a transformer, they have no idea which kind of load will be connected to the transformer. The load may be resistive (R), inductive (L), capacitive (C) or mixed load (R, L, and C). Its mean, there would be different power factor at the secondary (load) side. The output of real power may vary depending on the power factor. Thus the manufacturer denotes it as “this transformer can provide x number of amperes at y amount of voltage”. This way, they go for VA as in (voltage x Amperes) instead of W in case of  rating of transformer.

•  what are Transformer losses and their types

A real transformer has the following losses

• Copper Losses (Winding Resistance)

The losses occur due to the current flow through the windings that causes resistive heating of the conductors.

• Core or Iron Losses

There are two types of core or iron losses

• • Hysteresis Losses

These losses occur due to the magnetic field reversal. The magnetization & demagnetization of the core consumes some energy, also known as hysteresis loss.

• • Eddy Current Losses

The losses due to the current generated inside the core. The eddy current causes the resistive heating of the core.

Various other losses include:

• Stray losses (leakage Flux)
• Dielectric Loss
• Other Losses
  • Magnetostriction Losses
  • Mechanical losses

 

• what is voltage regulation of transformer

Voltage regulation in transformer is the percentage change in the secondary voltage from no load to full load condition. Ideally, the secondary voltage remains the same throughout the load, in which case the voltage regulation is zero. But practically it varies with the power factor of the load.

Basic electrical formulas

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