Instrument Transformer

In this article we will discuss about the instrument transformer . we learn about type of instrument transformer

Instrument transformer

The transformer which is used with measuring instrument and used to measure the high voltage and high current is called instrument transformer.
instrument transformer, types of instrument transformer, working of instrument transformer

Types of instrument transformer

There are mainly two types of instrument transformer

1. Current transformer

2. Potential transformer

instrument transformer, types of instrument transformer, working of instrument transformer

1. Current Transformer

The current transformer is used for measuring the current of high tension and extra high tension lines.it is a step-up transformer. It has a primary winding of few turns of even a single turn to carry the current to be measured and is connected in series with the main circuit. The secondary winding consists of more turns of thinner wire and connected across the ammeter terminals as shown in diagram.
Hence, the electric current of 100-200 A of primary circuit, is converted into the electric current of 1-2 A and this current is measured by the ammeter which is connected with the secondary as shown in figure below.

2. Potential transformer

instrument transformer, types of instrument transformer, working of instrument transformer


This type of transformer is used for measuring the voltage of high tension lines. It is a step-down transformer and is connected in parallel with the circuit. It has a primary winding of large number of turns of fine wire connected to the line whose voltage is to be measured. The secondary winding consists of few numbers of turns of thick wire and is connected across the low range voltmeter. For safety, secondary winding should be completely insulated from the high voltage primary and shoud be additionally grounded for providing protection to the worker.

Working of General transformer

When primary winding of transformer is connected with an AC supply, then due to the flow of alternating current, a magnetic flux or field of alternating nature is developed which completes its path through the common magnetic core. Hence these principle working on instrument transformer.
The conductors of secondary windings cross the magnetic field lines which were set up by magnetic field of primary windings, these results in producing field of primary windings, these results in producing the magnetic flux of alternating nature in secondary windings.
This flux induces and electromagnetic force according to the faraday’s law of electromagnetic induction.
In this way, without any connection or touch, an electrical energy is transferred between the primary and secondary winding, this action is called the transformer action. If now load is connected to the secondary winding, the induced EMF drives a current though it.

Advantages of Transformer (instrument transformer).

1. it is a static device and there is no movable parts in it and hence, no tear and wear of it.

2. it requires very little care and maintenance.

3. No attention or little attention is required for its operation so its maintenance cost is low.

4. its life is more.

5. the Voltage can be easily stepped up and stepped down according to the requirement.

6. it has a high efficiency.

7. transmission and distributing become cheaper, as a result aluminum or copper is saved.

Hence it is the instrument transformer if you will find any incorrect above please comment below.


For knowing more about instrument transformer you must watch this video. 


CRO Working and application

In this article we will discuss about the CRO working and application . we will also learn about the main working and application.

 CRO Working and application

CRO working and application, working of CRO, application of CRO
The oscilloscope is an electronic measuring device which provides a visual presentation of any wave form applied to the input terminals.

Cathode Ray tube (CRT) like a television tube provides the visual display of the signal applied as a waveform on the front screen. It is also known as cathode Tay oscilloscope (CRO).
Block Diagram of CRO
For better understand CRO working and application we need to know about the block diagram of CRO.

Block Diagram of CRO

For knowing about CRO working and application we required to also know about the block diagram of CRO.
CRO working and application, working of CRO, application of CRO
The Block diagram of CRO is shown below. It consists of various elements which must be known to us to understand the proper functioning of CRO.

1. Attenuator

The input signal should be  attenuated to a suitable magnitude before
it is applied to the amplifier. The attenuators are employed at the input of both vertical and horizontal amplifiers.

2. Amplifier

The amplifiers of an oscilloscope consist of a vertical amplifier and a horizontal amplifier. The vertical amplifiers amplify the vertical input signal before it is applied to the Y-plates. The horizontal amplifier amplifies the signal, before it is connected to the X-plates.

3. Saw-tooth Generator 

For better know about CRO working and application we required to know about Saw-tooth generator.
The measuring signal of any shape is connected to the Y-input (plates) and then it appears on the screen. The signal on X-plates should be such that the image on the screen is similar to that on the Y-plates. Hence, a saw tooth signal is required to be connected to the x-plates which make the image on the screen like the signal connected at the vertical plate.
The saw-tooth signal is called the time base signal, and is produced by the saw-tooth generator. The shape of the saw-tooth signal is shown in figure. The time base signal consists of trace, retrace and hood-off period.

4. Gate Amplifier or Z-amplifier

It is desirable that the image seen on the screen of the CRT must be continuous. The electron beam is desired to appear only in the trace period of the time base signal. The retrace period of the electron beam must not be visible on the screen. Therefore, the gate amplifier is required to control the electron beam in order that it’s appears only in the trace period. It is very important for CRO working and application.

5. Trigger (Gate Amplifier Output)

As mentioned earlier, the measuring signal waveform is connected to Y-input, which appears on the screen.
In order to make the waveform stationary on the screen, it is required that the starting point of the time base signal has to be fixed related to the signal connected to the Y-input. This is known as synchronization.
There are three forms of triggering in an oscilloscope. For better know about CRO working and application we need to know about this.

1. Internal triggering

The signal which is supplied to the trigger is the internal signal of the CRO produced by using the signal form the vertical input signal.

2. External triggering

The signal which is supplied to the trigger is the external signal, produced by using the signal from the external synchronous.

3. Line Triggering

The signal which is supplied to the trigger is the signal from the power supply of CRO (not shown).
Switches are provided to select the form of triggers as required. In a CRO, suitable timing can be selected that causes the image on the screen to be stationary.

Application of CRO

1. Measurement of current
2. Measurement of voltage
3. Measurement of frequency
4. Measurement of inductance
5. Measurement of admittance
6. Measurement of power factor
7. Measurement of resistance.

Hence it is the main CRO working and application. If you will find any incorrect above please comment below in comment box.


For knowing more about the CRO working and application you must watch this video.


Overcurrent Relay types

In this article we will learn about overcurrent relay types. We will also know that what is working of overcurrent relay and overcurrent relay type. Here we now discus about the overcurrent relay types and working.

Overcurrent Relay types and working

Relay is sensing equipment which senses abnormal voltage and current conditions in power system and sends signals to circuit breaker to remove faulty part from rest of power system.
overcurrent relay types, types of overcurrent relay, working of over current relay
First line of defense is provided by the primary relaying equipment and second line of defense is provided by the backup relaying equipment. Backup protection operates when primary protection has failed.

Overcurrent Relay types  

overcurrent relay types, types of overcurrent relay, working of over current relay


The operating time of all over current relays tends to become asymptotic to a definite minimum value with increase in the value of current. This is inherent in electromagnetic relays due to saturation of the magnetic circuit. These are following types of over current relay.
Instantaneous Over current Relay
In this relay, time of operation of relay does not depend on the value of actuating quantity once it is more than pick up value. This is property of electromagnetic attraction types of relay. Time of operation usually .1s. It is one of the overcurrent relay types.
overcurrent relay types, types of overcurrent relay, working of over current relay

Inverse Time current Relay

In this relay, there is an inverse relationship between actuating quantity and time of operation of the relay. All electromagnetic induction types of relay are inverse time current relays to some or large extent. It depends on how core iron gets saturated. If it saturates early, it becomes definite time current relay. It is main overcurrent relay types.

Inverse Definite Minimum time current Relay

In this relay time of operation of the relay is inversely proportional to current near pick up value and for values little after that. If current increases more, then that time of operation becomes constant.

Very inverse Relay

In this type of relay, core does not saturate early, and then inverse relationship can be introduced air gap in core. So, time current characteristics are inverse for larger values of current and then become definite time curve.

Extremely Inverse Relay

In this relay, saturation occurs at much later stage and current time curve is inverse for larger value of current curve.

Differential Relay

The principle of operation depends on a simple circulating current principle, where the difference of the currents of the two CT s flow through the relay under normal conditions or even under faults outside the protected section.

Protective Relay

Protective Relay and systems detect abnormal condition like fault in electrical circuit and operate automatic switch gear to isolate faulty equipment’s from the system as quickly as possible.
Protective relay functions are association with the switch gear to avert the consequences or faults. The switch gear must be capable of interrupting both normal currents as well as fault currents. The protective relay on the other hand must be able to recognize an abnormal condition in the power system and take suitable steps to ensure its removal with least possible disturbance to normal operation. It is also overcurrent relay types.

Hence it is the overcurrent relay typesif you will find any incorrect above please comment below in comment box.


For knowing more about overcurrent relay types you must watch this video.

Types of Starters

In this article we will learn about the types of starters and their working. We will also learn that how a induction motor start form a starter. We learn main types of starters which are used to starting of squirrel cage induction motor.

Types of starters


Following are the different types of starters used for starting of induction motors.
For squirrel cage induction motors various types of starters used as.

1. DOL (Direct-On-line) starter.

2. Star-Delta Starter

3. Autotransformer Starter

1. DOL Starter ( it is low capacity types of starters,direct online starter).

In case of small capacity motors having rating less than 5 HP, the starting current is not very high and these motors can withstand such starting current without any starter. Thus, there is no need to reduce applied voltage to control the starting current. Such motors use a type of starter which is used to connect stator directly to the supply lines without any reduction in voltage. Hence, the starter is known as Direct-on-Line starter.
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Though, this starter does not reduce the applied voltage, it is used because it protects the motor from various severe abnormal conditions like overloading, low voltage, single phasing etc. hence it is one of the types of starters which is used at below 5 HP motor.
The NO contact is normally open and NC is normally closed. At start, NO is pushed for fraction of second due to which, coil gets energized and attracts the contactor. So, stator directly gets supply. The additional contact provided, ensures that as long as supply is ON, the coil gets supply and keeps contactor in ON position. When NC is pressed, the coil circuit gets opened due to which coil gets de-energized and motor gets switched OFF from the supply. Under cover load condition, current drawn by the motor increases due to which there is an excessive heat produced, which increases temperature beyond limit. Thermal relays get opened due to high temperature, protecting the motor from overload conditions. It is main types of starter in squirrel cage induction motor.

2. Star-Delta Starter

If the stator winding of the motor is directly connected with the supply, it will draw a high current. To control this high current, star-Delta starter is used.  A star-Delta starter is used for a cage motor designed to run normally on delta connecting stator winding. A star-delta starter is used with a squirrel cage induction motor having a capacity up to 5HP. It is operated by a handle. It is manual types of starters.
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In start position, downwards, the stator winding are connected in star. The voltage on each winding will be equal to the line voltage under root three, that is 57.7% of line voltage. When the rotor gains speed, the starter is quickly changed to run position that is upwards, thereby connecting the stator winding in delta. In delta, the phase voltage is equal to the line voltage, therefore, full line voltage is applied to the stator winding and the motor will run at its normal speed. Hence it is also one of the types of starters which used at 5 HP.

3. Autotransformer starter

These types of starters are used for starting of the squirrel cage induction motors, having a capacity of 25 or more than 25HP. A three phase autotransformer, with many tapings in each winding is used in it as shown in figure.

types of starters, starter types , staring of induction motor , main types of starter

Three leads are taken out of the winding of the motor and connected with stator. At the time of starting, reduced voltage is applied to the stator winding of motor through these tapings.
The motor runs at a low speed, so that the current drawn by the motor reduces. As the motor attains about 75%  of the speed, the handle is put in run position and motor autotransformer is out of circuit. This starter is provided with no-volt and over load coils. Hence it is one of the types of starter which is used for high rating motor.
Hence it is the main types of starters which is used to start of squirrel cage induction motor. If you will find any in correct above please comment below in comment box.

For knowing more about the types of starters you must watch this video.


Transformer protection

In this article we will learn about how to do transformer protection. What we can prepare steps for transformer protection. We will discuss about the electrical device which is useful in transformer protection.

Transformer protection

transformer protection, protection of transformer, transformer fault
Fault in the transformer is of following when drawn on a graph.
Fault in Auxiliary Equipment’s
The following can be considered as auxiliary equipment’s of the transformer.

1. Transformer

2. Gas cushion

3. Oil pumps and forced air fans

4. Core and winding insulation

Winding fault

There may be faults between adjacent turns or parts of coils such as phase to phase faults another fault may be fault to ground or across complete winding such as phase to earth faults on the HV and LV external terminals.

Over-loads and external short circuits

Over-loads may be sustained for long periods, being limited only by the permitted temperature rise in the winding and the cooling medium. Excessive overloading will result in deterioration of insulation and subsequent failure.

Differential protection of transformer

transformer protection, protection of transformer, transformer fault
Differential transformer protection is the most important type of protection used for internal phase to phase and phase to earth faults and generally applied to transformer having rating of 5MVA and above. The differential protection of transformer is also known as merz-price protection for the transformer. A schematic diagram of differential transformer protection scheme for a star- delta power transformer shown in below fig.
In a star delta transformer, the load currents in the two winding are not in direct phase opposition but are displaced by 30 degree and to allow for this the CT secondary are connected in delta on the star side and in star on delta side.

Gas Actuated Rely-Buchholz Relay


The heat produced by internal fault or overloading of transformer oil to decompose and produce a gas which can be made to detect the winding fault. Buchholz relay is an electrical device which use to transformer protection form heating of winding.
Buchholz relay is a simplest form which is used in all transformers produced with conservator.

Bus-Bar Arrangements

Bus-bar are arranged to achieve

1. Adequate operating flexibility

2. Sufficient reliability

3. Minimum Cost

The cost can be minimized by reduced the number of circuit breakers to a minimum but complication of the protective gear are increased.

Some bus bar Arrangement

It is also main step in transformer protection.
In this arrangement a set of bus-bars is used for complete power station and to this bus bar are are connected all generators. Transformers and feeders through circuit breakers and isolating switches. Such a bus-bar arrangement is cheaper in initial as well as in maintenance cost and simple in operation and relaying.

Single Bus-bar system with sectionalisation

With increased number of generators and outgoing feeders connected to the bus-bars, it becomes essential to provide arrangement for sectionalizing the bus bars so that a fault on any one section of the bus-bars may not cause a complete shutdown. This is achieved by providing a circuit breaker and isolating switches between the sections. This is main step of transformer protection because bus bar proper arrangement is more important than other.

Ring bus-bar system

In this arrangement each feeder is supplied from two paths, so that in case of failure of a section, supply is not interrupted.

Double main and transfer bus bar Arrangement

 Double main and transfer bus bar arrangement is also important for transformer protection. This arrangement incorporates all advantages of the double bus as well as transfer bus-scheme. The scheme needs a bus-coupler for the on load transfer to circuits from one main bus to the other and a transfer coupler for taking out circuit breaker of various circuits for maintenance. Double main and transfer bus bar arrangement  is also important for transformer protection.
hence it is transformer protection if you will find any incorrect above please comment below in comment box.

For more about transformer protection you must watch this video.



Application of Diode

In this article we will learn about the main application of diode. we will discuss about the specification and temperature base application of diode. following  application of diode given below.
Application of diode, Diode application, Use of diode, specification of diode, temperature effect on diode

Application of Diode

1. Diodes are used in communication receivers for modulation and demodulation.

2. It is used as a switch in high speed digital circuit.

3. Diodes are used in rectifiers. In low power and high power rectification process.

4. With the use of diodes, we can form complex circuit diodes, varactor diodes, gunn diodes.
It is the some application of diode. 

Specification of diode

For knowing more about application of we need to know about the specification of diode.


Some of the specifications of the diode which are considered during manufacturing are as given below.


1. Semiconductor material

We know that diode is made of doped semiconductor material. This could be silicon or germanium. The material used in the p-n junction diode of great importance because cut-in-voltage or knee voltage depends upon the material of the diode. The material used also affects many of the major diode characteristic and properties.

2. Peak inverse Voltage (PIV)

The maximum voltage of a diode can withstand in the reverse direction is called the peak inverse voltage. This voltage must not be exceeded otherwise the device may be fail.

3. Forward Voltage drop

It is the voltage drop which appears across the diode when the maximum average current flows through it continuously.

4. Maximum forward current

It is the maximum current that a diode can allow to flow through it without getting demaed.

5. Maximum revers current

It is the maximum current that can flow through the diode when the maximum reverse voltage or PIV is applied.

6. Maximum Forward surge current

It is the forward current that can flow through the diode for a defined short period of time.

7. Maximum junction Temperature

It is the maximum temperature that a diode junction can withstand without getting damaged.

Some other application of diode

1. Diode use as rectifier. it is used in rectifier circuit for convert AC power into DC power .
In this article we will learn about the main application of diode. we will discuss about the specification and temperature base application of diode. following  application of diode given below. Application of diode, Diode application, Use of diode, specification of diode, temperature effect on diode Application of Diode  1. Diodes are used in communication receivers for modulation and demodulation.  2. It is used as a switch in high speed digital circuit.  3. Diodes are used in rectifiers. In low power and high power rectification process.  4. With the use of diodes, we can form complex circuit diodes, varactor diodes, gunn diodes. It is the some application of diode.  Specification of diode  For knowing more about application of we need to know about the specification of diode.  Some of the specifications of the diode which are considered during manufacturing are as given below.   1. Semiconductor material  We know that diode is made of doped semiconductor material. This could be silicon or germanium. The material used in the p-n junction diode of great importance because cut-in-voltage or knee voltage depends upon the material of the diode. The material used also affects many of the major diode characteristic and properties. 2. Peak inverse Voltage (PIV)  The maximum voltage of a diode can withstand in the reverse direction is called the peak inverse voltage. This voltage must not be exceeded otherwise the device may be fail. 3. Forward Voltage drop  It is the voltage drop which appears across the diode when the maximum average current flows through it continuously. 4. Maximum forward current  It is the maximum current that a diode can allow to flow through it without getting demaed. 5. Maximum revers current  It is the maximum current that can flow through the diode when the maximum reverse voltage or PIV is applied. 6. Maximum Forward surge current  It is the forward current that can flow through the diode for a defined short period of time.  7. Maximum junction Temperature  It is the maximum temperature that a diode junction can withstand without getting damaged.  Some other application of diode  1. Diode use as rectifier. it is used in rectifier circuit for convert AC power into DC power .  2. It is use as a amplifier .   3. its maximum used DC circuit or control circuit.   Temperature Effect on diode The application of diode is also depend on temperature effect on diode. The temperature has the following effects on the diode parameters.  1. The cut in voltage decrease as the temperature increases.  2. the reverse saturation current ( the current in case of reverse biasing of diode) increases as the temperature increases.  3. Reverse breakdown voltage is increased with increase in temperature.  If temperature is increased, the more number of electron –hole pairs are produced in the p-n junction diode. This results in increasing the current through the diode and the knee voltage is reduced.  Example Considered a p-n junction diode of silicon having knee voltage is 0.7V at 0 degree.  If the temperature is increased, the value of knee voltage is decreased as shown graph given below.   Hence it is the application of diode. if you will find any incorrect above please comment below in comment box.  For knowing more about the application of diode. you must watch this video.

2. It is use as a amplifier . 

3. its maximum used DC circuit or control circuit. 

Temperature Effect on diode

The application of diode is also depend on temperature effect on diode. The temperature has the following effects on the diode parameters.

1. The cut in voltage decrease as the temperature increases.

2. the reverse saturation current ( the current in case of reverse biasing of diode) increases as the temperature increases.

3. Reverse breakdown voltage is increased with increase in temperature.

If temperature is increased, the more number of electron –hole pairs are produced in the p-n junction diode. This results in increasing the current through the diode and the knee voltage is reduced.

Example
Considered a p-n junction diode of silicon having knee voltage is 0.7V at 0 degree.  If the temperature is increased, the value of knee voltage is decreased as shown graph given below. 

Hence it is the application of diode. if you will find any incorrect above please comment below in comment box.

For knowing more about the application of diode. you must watch this video.
   

Types of Semiconductors

In this article we will discuss about the types of semiconductors. We learn about N type and P type semiconductor working. We know about the main type of semiconductor.

Types of Semiconductors

There are two types of semiconductors which are...

1. Intrinsic semiconductors
2. Extrinsic semiconductors
types of semiconductors, semiconductor types , what is semiconductor

1. Intrinsic semiconductos

An intrinsic semiconductor is one which is pure. With no impurities. It has equal numbers of negative carriers. It has equal number of negative carriers and positive carriers. For example, a silicon crystal is an intrinsic semiconductor because every atom in the crystal is a silicon atom.
For knowing better about types of semiconductors, we need to know about formation of Holes
Formation of Holes
In an intrinsic semiconductor, when we provide sufficient that, then a valance electron of an element is moved away from the covalent bond and the covalent bond is broken and that electron becomes a free electron to move in a crystal. When this electron breaks a covalent bond moves away, a is known as hole. In other words, when a free electron is released, a hole is formed.  It is the one of the main types of semiconductor.

2. Extrinsic Semiconductor

An extrinsic semiconductor is the one which is made by adding impurities to an intrinsic semiconductor. The conductivity of a semiconductor can easily be modified by introducing the impurities into their crystal lattice. The process of adding controlled impurities to a semiconductor is called doping.


Based on the impurities added to the semiconductors, the two types of semiconductors are possible, that is N-type semiconductor and P-type semiconductor.
For knowing more about types of semiconductor we need know about N and P types of  semiconductor and their working.

N-type semiconductor

A semiconductor with surplus of electrons is known is known as N-type semiconductor. To obtain excess free electron, the elements such arsenic, antimony or phosphorous are doped in the semiconductor material. Each donor atom has 5 electrons (pentavailent) in its outer orbit.
When a donor atom replaces an atom in the crystal lattice, only four electrons are shared with the surrounding atoms. The fifth, valences becomes a free electron as shown in figure. As in the N-type semiconductors, the number of free electrons is greater than the number of holes so, the free electrons are the majority carriers and the holes are minority carriers.

P-types of semiconductors

A P-type semiconductor has surplus of holes. It is made by doping an element (accepter impurity) with semiconductor material. The elements like gallium, born or indium (trivalent) are the main accept-or impurities.
types of semiconductors, semiconductor types , what is semiconductor
We have studied the materials, which are the basic building blocks of electronic components and now we will study the electronic components which are made by their materials.
Hence it is the main types of semiconductors and their working. If you will find any incorrect above please comment below in comment box.

For knowing more about the types of semiconductors you must watch this video.