Why is Silicon Steel used in Generators and Transformers?

Silicon Steel is preferred over other steels to be used in transformers and generators because it improves the ability of magnetic fields to penetrate it, and reduces the hysteresis losses present in the steel. It can also reduce the rate of Corrosion but the Primary factor to Add Silicon to Steel is to reduce the Hysteresis Losses.

Silicon + Steel = Reduction of Hysteresis Losses.

Why Short Circuit test is performed on LV side?

A Short Circuit test is used to calculate the copper losses , load current and other values so in order to measure these values we have to apply meters , if the meters are connected to measure the values of Low Voltage ( LV ) side then it will be easy to find and use low voltage measuring meters, on HV side the meters required will be of higher range.

Difference Between Electrical and Electronics

Difference Between Electrical and Electronics

Electrical - A High Voltage of magnitude upto 440, 220, 132 KV etc. and a considerably low frequency - 50Hz, 60 Hz etc. Machines that fall under this category arr Power Transformers, Electrical Motors etc.

Electronics - A High Frequency ( of Mhz ) and considerably low voltage 5 V, 12 V etc.

Applications - Mobile Chargers, amplifiers, filters etc.


If you know some other differences please  comment below.

What is Electrical Resistance

Electrical Resistance is Denoted by 'R' and is the amount of opposition caused by a circuit in the flow of current.
Under normal/standard conditions The potential difference across the ends of a electrical circuit is directly proportional to the current flowing through it ,

Potential Difference is denoted by V and Current is denoted by I

when we remove the proportionality sign then a the equation becomes

V = IR
or I = V / R , Here R is the resistance offered by the circuit.

hence current is inversely proportional to the Resistance. It opposes the flow of current.

If we will plot a graph between V and I it will we a linear graph , as R is constant in this case.

Principle Of Electrical Machines By V.K. Mehta, Rohit Mehta | A free E-book

Can we give dc supply to transformers

This question is asked in many viva exams and by many users on the web. The simple answer to this question is NO ,
A transformer will never work on a DC supply (unless it is a Pulsating DC)

Reason : Transformers work on the principle of Electromagnetic Induction , the induced emf Depends upon the rate of change of flux and since there is no frequency of change in the DC supply ( A constant Magnitude ) these AC machines will not work on DC.

For AC machines to work an AC supply with some frequency is required for EMI ( Electro-Magnetic Induction to take place. )

Why do we need 3 point starters

A 3 point started is a device that is used in the starting of DC Shunt and DC Compound wound motors.
Due to a back emf in the motors the motor emf equation becomes

Emotor = Eback + I(armature) R(armature)

Since at the time of starting the value of Eback is negligible hence
Emotor becomes = Ia x Ra

Or Ia = Emotor / Ra

Hence starting current will be very high if the value of Ra is very low so we have to introduce more resistance at the time of starting to limit Ia hence a 3 Point Starter with Variable Resistance is used to start a motor.

Working of A DC Generator

Let us consider a single turn rectangular coil which is rotating in a anti-clockwise direction with angular velocity (w) radians per second in a uniform magnetic field of flux density B tesla ,
when the coil is rotated in a uniform magnetic field with uniform angular velocity an emf is induced in its coil sides and its magnitude depends upon B , the effective length of the coil 'l' number of turns in the coil 'N' , velocity of the coil side perpendicular to the field Vp :

hence the formula for the EMF becomes : E= 2NBlVp Volts

This is the generated emf .

PMMC Type Instruments - Application and Type of Damping Used

Type of Measurement Instrument

Moving Coil –

Permanent Magnet Type – DC measurements of Currents and Voltage only , Type of Control Used is Spring | Type of Damping Used is Eddy Current Damping | It is most accurate type of DC measurement instrument and is widely used for measurement of DC Voltage, Current and Resistance.

Type of Current in a mobile phone charger

In the input terminal AC is fed but it is converted to DC by means of a bridge wave rectifier mostly this is done in order to charge the battery since batteries run on DC power.

If we connect a USB to computer and connect the output end to mobile phone then DC from the USB output terminals of computer is directly supplied to Mobile's battery.


Here is a simple block diagram. 

Kirchhoff's Voltage Law - KVL

Kirchhoff's Voltage Law states that the total voltage around a closed loop in an electrical circuit must be zero. If a circuit contains more than one close loops then the total voltage in all the individual loops must also be zero, this signifies that electrostatic field is conservative.

A detailed explanation can be read in this link with good examples and figures :

http://www.physics.uoguelph.ca/tutorials/ohm/Q.ohm.KVL.html

Electrical Motors used in different loads / applications

Types of Electrical Motors Used for Different Loads / Applications

Name of Application	Type of Motor Used
Sewing Machines , Vacuum Cleaners, Mixers, Electric Shavers, Cloth Washing Machines etc	Small Universal motors of mostly series type.
Travelling Cranes 1.       Hoisting and lovering 2.       Crane travel, tolley and boom hoist 3.       Slew and swing action machines	AC Slip ring Motors, Ward Leonard Controlled Dc Shunt Motors and DC Compound Motors AC Slip ring Motors AC Slip ring Motors or Dc Shunt Motors
Lifts	AC Slip ring Motors or DC Compound Motors
Lathe Machines, Milling and Grinding Machines	DC Shunt or Squirrel Cage Induction Motors
Planers	DC Shunt or DC Compound or Slip Ring Induction Motors
Punches ,Press and Shears	High Slip Squirrel Cage
Shapers and Slotters machines	Constant Speed Squirrel Cage Induction Motors
Blowers and Fans	Squirrel Cage Induction Motors and Synchronous Motors
Flour Mills	Pipe-Ventilated or Totally Enclosed type Motors
Traction Loads	DC Series Motors – High Torque
Kiln Drives	Ward Leonard Controlled Dc Shunt Motors
Jaw Crushers	Belted – Slip Ring Induction Motors

Why do we use capacitors in ceiling fans

Ceiling Fans run on single phase supply, We use two capacitors in these fans and they are named as
Start Capacitor and Run Capacitor

To run the motor shaft (or the fan blades) a rotating magnetic field is needed.
To do this different phases are needed to be applied to different winding in order to run the motor and since there is a single phase supply hence these capacitors are used to provide a phase shift to the supply virtually making it working on a multiphase system.

This is the purpose of using capacitors in Ceiling Fans or single phase motors.

How do Solar Panels Work

Solar Panels are built with an array of small solar cells that work on the phenomenon of photovoltaic effect.
They convert the Energy from photons (sun-light) into electrical energy.
The surface of Solar Panels are exposed to sunlight to get the maximum possible sunlight and by PV effect the solar cells produce and electrical energy which is in DC.
All solar panels produce DC power which is converted to AC or fed to batteries by using DC controllers to charge the batteries , these batteries are connected to inverters if AC is needed.

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