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Friday, 17 March 2017

What is the Difference Between Short Circuit & Overload..???

Definition of Short-Circuit :

The circuit that allows the electric current to pass through the random path which has low resistance is known as the short circuit. The short circuit causes the heavy current which damages the insulation of the electrical equipment. It mainly occurs when the two wire touches each other or when the insulation between the conductor breaks down.

The magnitude of the short-circuit current becomes thousands time larger than the normal current. During the short circuit, the voltage at the fault point diminishes to zero and high magnitude current flow through the network. The short circuit has various harmful effects on the power system. They are

The short circuit causes a heavy current in the power system which produces excessive heat and hence results in fire or explosion.

The short-circuit produces the arc that causes the major damage to the element of the power system.

The short circuit affects the stability of the network which disturbs the continuity of the supply.

Definition of Overloaded :

The overload means more than the desires load impose on the power system network. The voltage at the overloads become diminished to a very low value, but it cannot be zero. The current in the overloaded condition is high but considerably lower than the short circuit current. The overloaded increase the temperature regarding joules, which causes burns and hence damage the electrical equipment.

The overloaded condition damage the equipment of the power system. For example – Consider the inverter has a rating of 400 watts, and if the load of 800 watts is connected across it, then this will cause an overload.

Comparison of Shart circuit & Overload :

One of the major difference between the short circuit and the overload is that the short circuit occurs because of the fault between the lines or line-to-earth whereas the overload means the equipment draw the excess of current from the supply. The other differences between them are explained below in the comparison chart.

The term overloaded is referred to the circuit or devices. The circuit is said to have overloaded when more than the desirable load is applied to the circuit. The overload occurs because of the malfunctioning of the equipment or faulty circuits. Whereas the short-circuit condition occurs when the metal wires come in contact with each other or because of insulation failures. The resistance of the devices during the short circuit becomes zero due to which the heavy current flow through the network.

Basis For Comparison	Short Circuit	Overload
Meaning	In the short-circuit the voltage at the fault point decreases to zero and current of irregular high value flow through the faulty point of the network.	The overload means that load greater than the desired value have been imposed on the system.
Voltage	Zero	The voltage becomes low, but cannot be zero.
Current	High	Low as compared to short circuit.
Occur	It occurs when the neutral and live wire touch each other.	It occurs when a large number of devices are joint in a single socket.

What is the Difference Between Resistance & Resistivity???

Differences

Definition of Resistance :

The resistance is the property of the material which creates an obstruction in the flow of the current. When the voltage is applied across the conductor, the free electrons starts moving in a particular direction. While moving these electrons collapse with atoms or molecules and hence produce heat. These atoms or molecules oppose the movement of free electrons in a material.

This opposition is known as the resistance. It is represented by the formula

Where ,

l – length of the conductor

a – cross section area of the conductor

ρ – resistivity of the material.

The SI unit of the material is ohms, and it is denoted by Ω at kΩ.

Factors Affecting Resistance :

The resistance of the wire increases with the length of the conductor.

It is inversely proportional to the cross section area of the conductor.

It depends on the material of the wire.

The resistance of the material depends on their temperature.

Definition of Resistivity :

The resistivity is also known as specific resistance. The resistivity represents the resistance of the material which has specific dimensions, i.e., the material has 1-meter length and 1 square meter area of cross section.

The formula represents the resistivity of the material

Where ,

l – length of the conductor

a – cross-section area of conductor

R – Resistance of the material

The SI unit of resistivity is ohm meter. The resistivity is directly proportional to the temperature of the material.The resistivity of the cube having one-meter side is defined as the resistance offered between the opposite two phases of the one-meter cube.

Comparison of Resistance & Resistivity :

One of the major difference between the resistance and the resistivity of the material is that the resistance opposes the flow of free electrons whereas the resistivity is the property of the material which defines the resistance of the material having specific dimension. The other differences between them are explained below in the comparison chart.

Basis For Comparison	Resistance	Resistivity
Definition	Property of substance due to which it opposes the flow of electrons.	It is defined as the resistance of material having specific dimensions.
SI Unit	Ohms	Ohms-meter
Symbol	R	ρ
Dependence	Length, cross-section area of conductor and temperature.	Temperature

What is the Difference Between Dielectric & Insulator..??

Differences

Definition of Dielectric :

The dielectric material is a type of an insulator which has some free electrons. It becomes polarised in the presence of the electric field. The polarisation is the property of the material in which the positive and negative charges of the material are shifted in the opposite direction. The polarisation reduces the overall field of the material.

The storage and dissipation of the electric energy are the main properties of the dielectric material. The conductivity of the perfect dielectric material is zero. The common example of the dielectric is the capacitor. The polarisation between the parallel plates of the capacitor increases the surface area of the capacitance.

Definition of Insulator :

The material which does not allow the electric current to pass through them is known as the insulator. The insulating material does not have any free electrons because their molecules have the strong covalent bond. The resistivity of the material is very high as compared with other material. Resistivity is the property of the material that shows the strong obstruction against the flow of charges.

The ebonite, paper, wood, plastic are some of the examples of insulators.

Comparison of Dielectric & Insulator :

The dielectric and insulator are differentiated from their applications. One of the major difference between the dielectric and insulator is that the dielectric stores the electrical charges while the insulator opposes the flow of electrons. Some other differences between them are explained below in the comparison chart.

Basis For Comparison	Dielectric	Insulator
Definition	The material in which an electric field can develop with the minimum loss of energy is known as the dielectric.	The substance which have low conductivity and which create obstruction in the flow of current in known as the insulator.
Polarize	Polarize in an electric field.	Can not polarize
Bond	Weakly bonded as compared to the insulator.	Covalent Bond
Dielectric constant	High	Low
Charges	Store the charges	Obstruction to the charges.
Example	Dry air, vacuum, distill water etc.	Cotton, plastic, mica etc.
Application	Capacitor, power cable etc.	Conducting wires, in high voltage system etc.

Thursday, 16 March 2017

Explain Difference Between EMF and Voltage???

Differences

Definition of Voltage :

Voltage is defined as the energy requires to moves the unit charge from one point to another. It is measured in volts and represented by the symbol V. The voltage is caused by the electric and the magnetic field.

The voltage is developed between the ends (i.e. the cathode and anode) of the source. The potential of the positive end point of the source is higher as compared to the negative points. When the voltage develops across the passive element, then it is called the voltage drops. The sum of the voltage drops in a circuit is equal to the EMF according to Kirchoff’s law.

Definition of EMF :

The energy supply from the source to each coulomb of charge is known as the EMF. In other words, it is the energy supply by some active source such as the battery to the unit coulomb charge. The EMF stands for the electromotive force. It is measured in volts and represented by the symbol ε.

The electromotive force of the above circuit is represented by the formula

Where,

r – internal resistance of the circuit.

R – External resistane of the circuit.

E – electromotive force.

I – current

Comparison of EMF & Voltage :

One of the major difference between the EMF and voltage is that EMF is the energy supplied to the charge, whereas the voltage is the energy requires to move the unit charge from one point to another. The other differences between them are explained below in the comparison chart.

Basis for Comparison	EMF	Voltage
Definition	The amount of energy supply by the source to each coulomb of charge.	Energy use by unit charge to move from one point to another
Formula	E= I ( R + r )	V=IR
Symbol	ε	V
Measure	Measure between the end point of the source, when no current flows through it.	Measure between any two points.
Source	Dynamo, electrochemical cell, transformer, solar cell, photodiodes etc.	Electric and magnetic field

What is difference B/N MCB & MCCB..???

Differences

Miniature Circuit Breaker (MCB) :

The miniature circuit breaker is an electro mechanical device which, automatically, switch off the circuit whenever the abnormal condition occurs. It easily senses the over current caused by the short circuit.

The working principle of the miniature circuit is very simple. Their main function is to protect the equipment from over current. It has two contacts one is movable, and the other one is fixed. When the current increases from the predefined limit, their movable contacts are disconnected from the fixed contacts which make the circuit open and disconnects them from the main supply.

Moulded Case Circuit Breaker (MCCB) :

The MCCB stands for moulded case circuit breaker. It is a protecting device which protects the circuit from overloading. It is mainly used in a place where adjustable tripping requires. The current rating of MCCB is up to 2500 amps. It is mainly used for high current applications. The MCCB has a manually operated switch for tripping the circuit.

The MCCB has two arrangements. One for the over temperature and the other for the over current. It consists bimetallic contact which expands and contracts when the temperature of the MCCB changes.

During the normal operating conditions, the contact allows the current to flow through the circuit. But as the current rises beyond the predefined value, then their contacts will warm and expand until the contacts are open. Thus, disconnected the circuit from the main supply and protects the equipment from damage.

Comparison of MCB & MCCB :

One of the major difference between the MCB (Miniature circuit breaker) and MCCB (Moulded case circuit breaker) is that the interrupt rating of the MCB is up to 1800 amps whereas the interrupt rating of the MCCB is between 10k – 200k amps. The other differences between them are explained below in details.

Basis for Comparison	MCB	MCCB
Definition	Type of switch which protects the system from overloaded current.	Protects the equipment from over temperature and fault current.
Abbreviation	Miniature Circuit Breaker	Moulded case circuit breaker.
Tripping circuit	Fixed	Movable
Pole	Available in single, two and three versions.	Available in single, two, three and four versions.
Interrupting Rating	1800 A	10k -200k
Remote on / off	Not Possible	Possible
Rating Current	100 amps	10 - 200 amps
Applications	In lightning circuit and for low loads.	In heavy current circuit
Uses	For domestic purpose.	For commercial and industrial use.

Tuesday, 14 March 2017

What is the Difference Between Volt & Amp..???

Differences

One of the major difference between the volt and amp is that the volt is the SI unit of the voltage, potential difference and electromotive force whereas the amp is the SI unit of the current. The volt and amp are differentiated below on the various other factors.

Comparison of Volt and Amp :

Basis For Comparison	Volt	Amp
Definition	It measure the force that causes the electron to flow through the conductor.	Measures the rate of flow of electrons through the conductor.
Formula	Joule / coulomb	Coulomb / second
Abbreviation	V	A
Measuring Quantity	Voltage, electromotive force and potential difference.	Electric current.
Measuring Instrument	Voltmeter	Ammeter

Definition of Volt :

Volt measure the work done by an electric charge to move from one end to another. It is the unit of the potential difference, electric potential and electromotive force. The volt is represented by the symbol V. Micro-volt, millivolt, kilovolt, and mega volt are the sub unit of the volts. One volt is equal to the work done by one joule to charge the body at one coulomb.

Definition of Amp :

The ampere is the SI unit of electric current. It measures the rate of flow of electric charge flow through the conductor. It is represented by the symbol A. One ampere is equal to the one coulomb of charge which is mathematically equal to the 6.242 X 1018 times the elementary charge.

Differences Between Volt and Amp :

The volt measure the force which causes the electrons to flow through the conductor whereas the amp measure the rate of flow electrons.

Volt is equal to the ratio of joule per coulomb whereas the amp is represented by the coulomb per second.

The volt is represented by the symbol V and the ampere is represented by the symbol A.

The volt is the unit of potential difference, voltage and electromotive force, whereas the amp is the unit of current.

The volt is measured by the voltmeter whereas the amp is measured by the ammeter.

The volts and amp both are correlated with ohms law.

Monday, 13 March 2017

Explain Difference Between Grounding and Earthing ???

Differences

One of the major difference between the grounding and the earthing is that in grounding, the current carrying part is connected to the ground whereas in earthing the non-current carrying parts is connected to ground. The other differences between them are explained below in the form of the comparison chart.

Comparison Grounding V/S Earthing :

Basis For Comparison	Grounding	Earthing
Definition	The current carrying part is connected to ground.	The body of the equipment is connected to ground.
Location	Between the neutral of the equipment and ground	Between the equipment body and earth pit which is placed under the earth surface.
Zero Potential	Does not have	Have
Protection	Protect the power system equipment.	Protect the human from electric shock.
Application	Provide the return path to the current.	It discharges the electrical energy to the earth.
Types	Three (Solid, Resistance and Reactance grounding)	Five (Pipe, Plate, Rod earthing, earthing through tap and strip earthing)
Color of wire	Black	Green
Use	For balancing the unbalance load.	For avoiding the electrical shock.
Examples	Neutral of generator and power transformer is connected to ground.	The enclosure of the transformer, generator, motor etc. are connected to the earth.

Definition of Grounding :

In grounding, the current carrying parts are directly connected to the ground. The grounding provides the return path for the leakage current and hence protect the power system equipment from damage.

When the fault occurs in the equipment, the current in all the three phases of the equipment become unbalance.The grounding discharges the fault current to the ground and hence makes the system balance

The grounding has several advantages like it eliminates the surge voltage and also discharge the over voltage to the ground. The grounding provides the great safety to the equipment and improves the service reliability.

Definition of Earthing :

The ‘earthing’ means the connection of non-current carrying part of the equipment to the earth. When the fault occurs in the system, then the potential of the non-current part of the equipment raises, and when any human or stray animal touch the body of the equipment, then they may get shocked.

The earthing discharges the leakage current to the earth and hence avoid the personnel from the electric shock. It also protects the equipment from lightning strokes and provides the discharge path for the surge arrester, gap and other devices.

The earthing is achieved by connecting the parts of the installation to the earth by using the earth conductor or earth electrode in intimate contact with the soil placed with some distance below the ground level.

Differences Between Grounding and Earthing :

The earthing is defined as the connection of the non-current carrying part like the body of the equipment or enclosure to earth. In grounding the current carrying part like neutral of the transformer is directly connected to the ground.

For grounding, the black colour wire is used, and for earthing the green colour, the wire is used.

The grounding balanced the unbalanced load where as the earthing protect the equipment and human from an electrical shock.

The grounding wire is placed between the neutral of the equipment and the earth whereas in earthing the earth electrode is placed between the equipment body and the earth pit which is placed under the ground.

In grounding the equipment is not physically connected to the ground, and the current is not zero on the ground, whereas in earthing the system is physically connected to the ground and it is at zero potential.

The grounding gives the path to an unwanted current and hence protects the electrical equipment from damage, whereas the earthing decrease the high potential of electrical equipment which is caused by a fault and thus protects the human body from the electrical shock.

The grounding is classified into three types. They are the solid grounding, resistance grounding and reactance grounding. Earthing can be done in five ways.The different methods of earthing are the pipe earthing, plate earthing, rod earthing, earthing through tap and strip earthing.

Specifications for Earth Electrodes :

The earthing electrode should not be placed near the building whose installation system is earthed more than 1.5 m away.

The resistance of the earth wire should not be more than 1 ohm.

The wire use for electrode and circuit should be made up of the same material.

The electrodes should be placed in vertical position so that it can touch the layers of the earth.

The size of the conductor should not be less than 2.6 mm2 or half of the wire used for electrical wiring. Bare copper wire is used for earthing and grounding. Green 6 THHN (Thermoplastic high heat neutral coating wire) and gauged copper wire of different sizes like 2,4,6,8 etc. are also used for earthing and grounding.

Monday, 6 March 2017

Difference Between Core Type and Shell Type Transformer..???

Differences

Core Type and Shell Type Transformer :

One of the major difference between the core type and the shell type transformers is that in core type transformer, the winding encircles the core, whereas, in shell type transformer, the core encircles the winding of the transformer. Some other differences between them are explained below in the form of the comparison chart.

Comparison of Core Type V/S Shell Type Transformer :

Basis for Comparison	Core Type Transformer	Shell Type Transformer
Definition	The winding surround the core.	The core surround the winding.
Lamination Shape	The lamination is cut in the form of the L strips.	Lamination are cut in the form of the long strips of E and L.
Cross Section	Cross-section may be square, cruciform and three stepped	The cross section is rectangular in shape.
Copper Require	More	Less
Other Name	Concentric Winding or Cylindrical Winding.	Sandwich or Disc Winding
Limb	Two	Three
Insulation	More	Less
Flux	The flux is equally distributed on the side limbs of the core.	Central limb carry the whole flux and side limbs carries the half of the flux.
Winding	The primary and secondary winding are placed on the side limbs.	Primary and secondary windings are placed on the central limb
Magnetic Circuit	Two	One
Losses	More	Less
Maintenance	Easy	Difficult
Mechanical Strength	Low	High
Output	High	Less
Natural Cooling	Does not Exist	Exist

Definition of Core type Transformer: The magnetic core of the transformer is made up of laminations to form a rectangular frame. The laminations are cut in the form of L-shape strips shown in the figure below. For avoiding the high reluctance at the joints where laminations are butted against each other the alternate layer are stacked differently to eliminates continues joints.

The primary and secondary windings are interleaved to reduce the leakage flux. Half of each winding is placed side by side or concentrically on the leg of the core as shown in the figure below. For simplicity, the primary and secondary winding are located on the separate limbs of the core.

The insulation layer is provided between the core and lower winding and between the primary and the secondary winding. For reducing the insulation, the low winding is always placed near to the core. The winding is cylindrical in shape, and the lamination is inserted later on it.

Definition of Shell Type Transformer : The laminations are cut in the form of a long strip of E’s, and I’s as shown in the figure below. To reduce the high reluctance at the joints where the lamination are butted against each other, the alternate layers are stacked differently to eliminate continuous joint.

The shell type transformer has three limbs or legs. The central limb carries the whole of the flux, and the side limb carries the half of the flux. Hence the width of the central limb is about to double to that of the outer limbs.

The primary and secondary both the windings are placed on the central limbs. The low voltage winding is placed near the core, and the high voltage winding is placed outside the low voltage winding to reducing the cost of insulation placed between the core and the low voltage winding. The windings are cylindrical in shape, and the core laminations are inserted on it.

Differences Between Core Type and Shell Type Transformer :

In core type transformer the core surrounds the windings whereas in shell type transformer the winding surrounds the core of the transformer.

In core type transformer the lamination is cut in the form of L-shape whereas in shell type transformer, the laminations are cut in the E and L shapes.

The cross-section area of the core type transformer is rectangular in shape, whereas the cross section area of the shell type transformer is square, cruciform two slipped or three stepped in shapes.

The core type transformer requires more copper conductor as compared to shell type transformer because in core type transformer the winding is placed on the separate limbs or legs.

The core type transformer is also called cylindrical or core winding transformer because their windings are arranged as the concentric coil. In shell type transformer, the low voltage winding and the high voltage winding are put in the form of the sandwich and hence it is called the sandwich or disc winding transformer.

The core type transformer has two limbs, whereas the shell type transformer has three limbs.

The mechanical strength of the core type transformer is low as compared to shell type transformer because the shell type transformer has bracings.

The core type transformer required less insulation as compared to shell type transformer because shell type transformer has three limbs.

In core type transformer the flux is equally distributed to the side limb of the transformer whereas, in shell type transformer, the central limb carries the whole of the flux and the side limbs carry the half of the flux.

In core type transformer both the primary and the secondary windings are placed on the side limbs whereas in shell type transformer, the windings are placed on the central limbs of the transformer.

The core type transformer has two magnetic circuits whereas the shell type transformer has one magnetic circuit.

The losses in a core type transformer are more as compared to shell type transformer because the core type transformer consists two magnetic circuits.

In core type transformer few windings are removed for maintenance. In shell type transformer numbers of the winding are required to remove for the maintenance.

The output of the core type transformer is high because it has fewer losses as compared to the shell-type transformer.

The winding of the shell type transformer is distributed type, and hence heat is dissipated naturally, whereas, in core type transformer, the natural cooling is not possible.

The laminations of both the transformer are made up of high-grade silicon steel. The lamination reduces the eddy-current loss, and silicon steel reduces the hysteresis loss.The laminations are insulated from each other by using the enamel insulation coating.

Difference Between Lap & Wave Winding...???

Differences

Lap & Wave Winding :

The insulator conductor house in an armature slot is known as an armature winding. In armature winding, the conversion of power takes places, i.e., in the case of the generator the mechanical power is converted into an electrical energy and in the case of a motor the electrical energy is converted into mechanical energy.

The armature winding is mainly classified into two types, i.e., the lap winding and the wave winding. One of the major difference between them is that in a lap winding the end of each coil are connected to the adjacent segment whereas in the wave winding the end of armature coil connected to commutator segment at a distance apart.

Comparison of Lap V/S Wave Winding :

Basis For Comparison	Lap Winding	Wave Winding
Definition	The coil is lap back to the succeeding coil.	The coil of the winding form the wave shape.
Connection	The end of the armature coil is connected to an adjacent segment on the commutators.	The end of the armature coil is connected to commutator segments some distance apart.
Parallel Path	The numbers of parallel path are equal to the total of number poles.	The number of parallel paths is equal to two.
Other Name	Parallel Winding or Mulitiple Winding	Two-circuit or Series Winding.
EMF	Less	More
Number of Brushes	Equal to the number of parallel paths.	Two
Types	Simplex and Duplex lap winding.	Progressive and Retrogressive wave winding
Efficiency	Less	High
Additional Coil	Equalizer Ring	Dummy coil
Winding Cost	High (because more conductor is required)	Low
Uses	In low voltage, high current machines.	In high voltage, low current machines.

Definition of Lap Winding : In lap winding, the consecutive coils overlap each other. The first end of the winding is connected to the one segment of the commutator, and the starting end of the other coil is placed under the same magnet (different pole) and join with the same segment of the commutator.

The conductors are connected in such a way that the number of parallel paths equals to the number of poles. Consider the machine has P poles and Z armature conductors, then there will be P parallel paths, and each path will have Z/P conductors in series. The number of brushes is equivalent to the number of parallel paths. The half of the brush is positive, and the remaining is negative.

The lap winding is mainly classified into two types. They are the Simplex lap winding and the Duplex Lap winding.

Simplex Lap Winding : In this winding, the number of parallel paths is equal to the number of poles.
Duplex Lap Winding : In duplex lap winding the number of parallel paths is twice to the number of poles.

Definition of Wave Winding : The one end of the coil is connected to the starting end of the other coil which has the same polarity as that of the first coil. The coils are connected in the wave shape and hence it is called the wave winding. The conductor of the wave winding are split into two parallel paths, and each path had Z/2 conductors in series. The number of brushes is equal to 2, i.e., the number of parallel paths.

Differences Between Lap and Wave Winding :

In lap winding, the coil is lap back to the succeeding coil whereas in the case of the wave winding the coil are connected in the wave shape.

In lap winding, the end of the armature coil is connected to the adjacent commutator segment, whereas is wave winding the end of the armature coil is placed in the commutator segment which is placed apart.

In lap winding the number of parallel paths is equal to the total number of poles of the coil and in the wave winding the number of parallel paths is always equal to two.

The lap winding is also called parallel winding because their coils are connected in parallel whereas in the wave winding the coils are connected in series and hence it is called series winding.

The emf of the lap winding is less as compared to wave winding.

The lap winding requires equaliser for the better commutation. The wave winding requires the dummy coil for giving the mechanical balance to the armature.

In lap winding, the number of brushes is equal to the number of parallel paths whereas in wave winding the number of brushes is two.

The efficiency of the lap winding is less as compared to the wave winding.

The simplex and duplex are the types of lap windings. In simplex winding, the number of parallel paths is equal to the pole, in duplex winding the pole is twice to that of a parallel path, whereas the progressive and the retrogressive are the types of the wave windings.