2020

Electrical Knowledge

Electrical and Electronic Concepts

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Rotor of Squirrel Cage Induction Motor

Tuesday, December 15, 2020

Transmission Line and Feeder

Posted by Pranshu Bahuguna on December 15, 2020 No comments

Four Types Of  Distribution Feeders Systems:

  • Radical 
  • Parallel Feeders
  • Ring Main
  • Meshed

 Radical :

Radical is the simplest and least expensive to construct. This is used when the generating station is at the center and different feeder radiate to the different direction and power flow is only in one direction.

So, it has one feeder line for the group of customer. If some problem such as power failure, short circuit arises at one spot, entire feeder  line will go down.

Parallel Feeders :

This feeders system is used when we need continuous power supply for 24 hours. In this feeder system a parallel separate feeder line is followed with the main feeder line. Whenever there is a fault in the main line, the power didn't cut at the consumer and is fed from the separate feeder line, this is the main advantage of the parallel feeder over the radical feeder.

The main disadvantage is the construction cost of the parallel feeder is more. 

Ring Mesh :

Ring mesh is quite similar to the parallel feeder but in this the distribution transformer is fed up with two different feeder, from two different path, and form a ring structure. This system is reliable as the distribution transformer is fed up with two feeder and if the fault comes in one feeder. The continuity supply of Electrical power didn't stop.

Meshed System:

When the ring meshed system is energized by two or more generating station is known as meshed system.

Types of Transmission line on the basis of distance:

  • Short Transmission Line ranges from zero to 80 Km and operating voltage of 0 to 20 Kilovolt. Shunt capacitance is so small that it can be omitted entirely with little loss of accuracy.

  • Medium transmission  line ranges from 80 to 200 km and operating voltage of 20 to 100 kilovolt.
  • Long transmission line ranges from 80 to 200 km and operating voltage above 100 kilovolt. Mho relay is used in long transmission line.

A small LT line is a lower voltage Line which is 230 volt for single phase supply and 400 volts for 3 phase supply.

HT Line is for High Voltage Line which starts from 11 kV, 33 KV, 220 KV, 400 KV and more.

Note:

A Transmission line is used in reference to the transmission system and used for sending Electrical power from the generating Station to the substation. Power is Transmitted via transmitted line to the substation, where transmission voltage are more than 132KV

A Feeder is used with respect to the distribution system and used for sending power from substation to the consumer/load end. 

Characteristic Impedance

When the receiving end voltage is equal to IZ, the current and voltage waves are travelling in one direction, without any reflection of either current and voltage waves. The line is terminated in its characteristics impedance Zc and line is known as infinite line.

Ferranti effect.

When long or medium transmission line is open circuit or on light load the receiving end voltage is greater than the sending end voltage, this effect of increase in the voltage at the receiving end is known as the Ferranti effect. This effect is absence in short transmission line because of negligible shunt capacitance.

Monday, November 9, 2020

TRANSISTORS AS A SWITCH

Posted by Pranshu Bahuguna on November 09, 2020 No comments

Transistors 

In 1947,The world of electronic devices is completely changed by the two physicists
John Bardeen and Walter Brattain when they made the first working device on point contact transistor.
Transistor are the semiconductor  device having three terminals, used as a switch or to amplify a current. They are very light in weight around 1gram or less and very small in size. The phone that you are carrying is light in weight and have small size that fit in your hand  because of the transistors.
Transistors can used as a switch in digital electronics and as an amplifier in the analog electronics. 

Transistors have 3 terminal:
1.Emitter
2.Base
3.Collector

Emitter is the source of charge carrier and that is why it is heavily doped. 
Base is lightly doped and very thin in size 
https://electricsknowledge.blogspot.com/2020/11/transistors_9.html
Transistor
Collector is moderately doped and wider in size than base and emitter region because collector main's job is to collect charge carrier from base and emitter region



Active region:


When the base emitter region is forward bias and collector and base region is reversed  bias. 
For this condition :
Base voltage must be higher than emitter voltage and Vbe =0.7 Volts
Collector voltage must be higher than base voltage so than collector voltage is higher than the other region voltage. 
The base current is directly proportional to the collector current. 

Transistor act as  a switch:

Transistor can act as a solid state switch that doesn't require any moving part, it act as a on/off switch just by sending a base signal.

For transistor to act as a switch:
  • Emitter is connected to the Ground.
  • Base is connected to the on/off signal with a  resistor
  • Collector is connected to the 5v supply.
Resistor is connected with the base terminal because base current should not be of high ampere, it can damage the transistor.

When a base current is flow through the transistor. So, it will create a path for the Emitter electron to flow through base region  to the  collector region and the current will easily flow through the collector region to the emitter region and act as a short circuit path. Transistor act as ON switch.
When base current is remove the collector current can't cross the base region and act as a open circuit or OFF switch.

So, in this way transistor can act as a switch



Difference between Earthing and Grounding.

Posted by Pranshu Bahuguna on November 09, 2020 , 2 comments



Earthing:

Earthing means connection of the non current carrying part of electrical equipment to the Earth. 

Advantage:

  • During fault condition if current flows through the equipment's, the chances of getting shock to the electrician will increases, if Earthing is done then all the current will be drawn to the Earth because equipment is in some potential during fault condition  and Earthing point is in zero potential ,then all the current will be drawn to the Earth and chances of getting shock will decreases. 
Earthing and Grounding

Grounding:

Grounding is connection of the neutral wire(which carry return current)  to the Earth.

Application:

  • Grounding is done of neutral point of the star connected transformer.
  • Grounding wire of lighting arrester is connected to the Earth which provide current path to the Earth. 
  • During fault condition all the excess current is transfer to the Earth to the safety of the electrical equipment's

Note:

Ground in electronics doesn't mean wire is physically connected to the Earth it simply refers to the zero potential from the other points.


Thursday, October 8, 2020

Power Factor

Posted by Pranshu Bahuguna on October 08, 2020 No comments

 Power Factor

Power factor is normally the phase difference between the voltage and current. Power factor is due to the inductive nature of the circuit, however, in resistor the voltage and current are in phase with each other. So, the power factor of the resistive load is unity and reactive power is zero. All the power is active power in resistor. Power Factor is the cosine of active power and he reactive power and maximum value of cosine is one. Therefore the power factor of a load can never be more than one.

  • Power factor is said to be lagging when the current lags the voltage by some angle, due to the inductive nature of the load. 
  • Power factor said to be leading if the current leads the voltage by some angle, due to the capacitive nature of the load.

Active Power:

Active power the main power which is consumed by the load. The main components of power which is used by the ac circuit to do some work. It is measured in KW.

Reactive Power:

Reactive power is the component of the total power which is travel along the active power but not used by the load. It  just travel back and froth in the load. It is used to establish the magnetic field in the motor or other alternating current equipment.

Apparent Power:

The total of the active power and the reactive power is known as apparent power

Electrical Motor : Comparison

Posted by Pranshu Bahuguna on October 08, 2020 No comments


Synchronous Motor Vs Induction Motor

Speed Vs Load:

In Induction motor and DC motor, the speed decreases when we increases the load. The decrease in the speed reduces the counter EMF, the additional current is drawn from the motor. If we add more load on the motor, the motor will draw more current which increase the iron losses and more heat will be dissipated, that can cause failure of insulation, faults can occur.

In Synchronous motor, the speed doesn't decrease with the increase in the load, it runs at synchronous speed at all loads. It meets the increased load by the relative shift btw the rotor and stator poles i,e by the adjustment of the torque angle. If the motor load increases , the torque angle increase which causes a greater phase shift of back EMF w.r.t supply voltage. This increases the voltage in stator winding and consequently, armature current will be drawn .

Disconnection of one phase:

If one phase of the three phase motor is disconnected due to some faults, more current will be drawn from the remaining two phase which can cause many failure. It also increases the iron losses. If it continue to draw more current , there can be motor failure or motor burnout.

Power Factor:

Synchronous motor can operate from lagging to leading power factor while the induction operates at the lagging power factor. A synchronous motor can generate and absorb reactive power by adjusting the excitation of the motor. Overexcited synchronous motor under no load condition can be used for power factor corrective device and known as synchronous condenser.

Supply :

Synchronous motor are doubly fed motors: Rotor require dc excitation and Stator require 3 phase ac supply. Induction motor only require 3 phase AC supply.

Self-starting:

Induction motor is self starting because of this construction: Squirrel cage helps the motor to be self starting.
Synchronous motor is not self starting, it require extra dc excitation at the rotor to produce magnetic pole to get lock with synchronous magnetic field revolving around the rotor.






Friday, October 2, 2020

Capacitor

Posted by Pranshu Bahuguna on October 02, 2020 No comments

Electrolytic capacitor:

Electrolytic capacitor uses electrolyte to achieve large value of capacitance than the other capacitor types.
Electrolytic capacitor always connected in forward bias ie Anode voltage must be in  higher voltage than the cathode voltage. If it is connected in reversed bias it act as a short circuit 

Application :
It is used power supply as a filtrating devices to reduce the ripple in voltage.
And 
In the low pass filter for the input and output smoothing and doesn't work in large amplitude and high frequency signal.
Electrolytic Capacitor
Electrolytic Capacitor

Capacitance:

Capacitance is the measurement of charge stored in the capacitor. Farad is the S.I. unit of capacitance.
We generally, don't use 1 farad of capacitance because 1 farad is a huge value of capacitance, if we want to make a  1 Farad capacitor, it will occupy a half space in your room.
However, we uses very less power capacitance for household purposes. Generally we uses 2.25 microfarad capacitor in our 220v Fan and all our tv, computer  and laptop have capacitor have capacitor which have value:1*10-12.

Ceramic Capacitor:

Ceramic capacitor is a fixed value capacitor which is made up of ceramic dielectric that's why gets the name: ceramic capacitor. Ceramic capacitor are small in size and are in the range of few picofarad to microfarad. These are used for coupling and decoupling applications.
 



Sunday, September 27, 2020

Types Of DC Motor / Induction Motor & Characterstics

Posted by Pranshu Bahuguna on September 27, 2020 No comments

Friday, September 25, 2020

Load Factor

Posted by Pranshu Bahuguna on September 25, 2020 No comments

 Load Factor

Load factor is define as average power consumption over a period to the peak power consumption over the same period. Load factor is very important in determining the generation of  cost per unit. Higher the load factor , lesser is the generation cost.

Load factor is calculated:

  • Daily
  • Weekly
  • Monthly 
  • Yearly
Load factor must always be less than one. We should never use all the equipment's of our house simultaneously. If one high power equipment is running ,we should not turn on the second equipment, wait and turn on the the other equipment's when the first work is finished.  

This will improve the load factor and giving us the low generating power cost



Tuesday, September 22, 2020

Rotor of Squirrel Cage Induction Motor

Posted by Pranshu Bahuguna on September 22, 2020 No comments

Squirrel Cage Induction Motor 

In Squirrel Cage Induction  Motor, the rotor conductor are permanently shorted by the Aluminum /Copper ring called the end ring forming a complete closed circuit like squirrel cage , That's why it is known as Squirrel Cage Induction  Motor

Construction:

Rotor:

The rotor is in cylindrical in shape. It consists of  two rings which are permanently shorted with each others by parallel  aluminum bars which are a slightly skewed to prevent the magnetic locking of the stator and the rotor teeth, makes the working of motor more smooth and quiet. Rotor resistance is very small and as the bars of the rotor is permanently shorted, no external resistance can be added.


Rotor Of Induction Motor


Insulated iron core lamination are inserted in squirrel cage rotor to aid the current loss in the rotor bars.

I hope you love this article, for any query please comment.
For Basic Information of Electricity





Single Phase Induction Motor

Posted by Pranshu Bahuguna on September 22, 2020 No comments

Single Phase Induction Motor 

The single phase induction motor is Classified into 4 motor 
  1. Split Phase Induction Motor
  2. Capacitor Start Induction Motor
  3. Capacitor Start Capacitor Run Induction Motor
  4. Shaded Pole Induction Motor

                                  Split Phase Induction Motor

The stator has two winding i.e Main winding/Running winding and Auxiliary winding/Starting winding. A centrifugal switch is connected in series with the auxiliary winding,to disconnect the auxiliary winding from the main winding when the motor achieves a speed of 70-80% of synchronous speed.

Working: 

Auxiliary winding is 90 Degree in phase with the main winding.The running winding  is inductive in nature that means current lags the voltage by an angle and the auxiliary winding is resistive in nature that means the current and voltage are in phase with each other.
To create a phase difference between 2 winding the starting winding must carry high resistance.
The result of these 2 current i.e Itotal  which produces the rotating magnetic field which rotates in one direction.

As the starting and main current splits from each other by some angle hence this motor is called Split Phase Induction Motor 

Advantages:

  • Motor have low starting Current
  • Motor have low starting Torque
  • Motor are used in fans, blowers, centrifugal pumps 

Application Of Single Phase Motors:

Shaded Pole induction motor are available to run with speed as low as one r.p.m.

Universal Motor/Single Phase Series Motor is used for the purpose of high speed and speed control is required. such as vacuum cleaners, drill machines. 


Test on Dc Motor

Posted by Pranshu Bahuguna on September 22, 2020 No comments
Swinburne Test

This test is used to determine the efficiency, losses and temperature ries on the dc machines. This test is perform on the large shunt dc machines. 

Hopkinson Test

This test is perform with the help of two shunt machine.   Both  machine are couplled together mechanically and electrically. 
One act as a motor and other as a generator. The output of the motor is connected to the input of the generator and output of the generator connected to the input of the motor. 

Saturday, May 16, 2020

Sensor and Transducer

Posted by Pranshu Bahuguna on May 16, 2020 No comments
Transducer

Transducer:

Transducer is a device that converts one form of signal into the other form of signal.

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJSu3DjHxwiLMJxhh2d8oBQAmEg_KbkbSdhTsBw8RZw6WLCir7EFIDVR86xlkhkIJdYoVf4rBbC9KBK91uGlfWB-S3NmODduYOkmeGHHCUmx-AMWRJVtIfQNasUAtiNTMnwvBfJRCcEuc/w640-h170/Transducer.jpg.png
Transducer
                                    
The input is given to the Sensor and the output of sensor is the input of Processor.The combine process of sensor and processor is a Transducer in which the sensor converts the physical quantity into electrical signal and processor continue the further process.
Now the Processor output electrical signal is given to the Actuator which coverts the electrical signal to the mechanical works,which is also an example of transducer.

Examples:
Microphone: Convert voice to Electrical signal
Speaker: Convert Electrical signal into Sound
Antenna: Converts Electromagnetic energy into electrical and vice versa
Strain Gauge : Convert strain to electrical. Strain gauge is a sensor that converts strain(Force) into the electrical signal,its resistance changes with the applied force on it and force magnitude can be easily measured.


Sensor:

Sensor is a device that converts physical quantity into electrical signal.
Example: Temperature and humidity sensor- DH22,

PIR Sensor: Passive Infrared Sensor is an Electronic device that measures infrared light radiation emitting from the object in its range.Generally, PIR can detect any Human/Animal movement in a range,the sensor doesn't emit any energy but passively receives and detect infrared energy from the environment.
PIR Sensor

Ultrasonic Sensor: It is an optical sensor and can detect how far an particular object is placed.It uses a transducer to send and receive ultrasonic sound waves that gives an approximation distance of the object from the sensor.
Ultrasonic Sensor

LDR Sensor :Light Dependent Resistor has a variable resistance which is the function of intensity of light falls on the surface of sensor. Its resistance decrease with the increase in the intensity of light falling on it. LDR can be used in the street light to automatically switchs on and off the lights when it requires.

LED: Led is a semiconductor which emit lights when current flows through it.
Led has two terminal:
Anode which is long terminal and positive in nature.
Cathode which is short and negative in nature.
Current aways flows from the anode to Cathode in LED and never in the opposite terminal.
The operating voltage of LED is around 1.8 to 3.3 volts it varies by the color of LED.Current varies from 10mA to 20mA which maximum current capacity of LED. It will burn out, if current more than 20mA goes in the LED.
Always, a Resistor is connected in series with LED to limit the current through the LED. The resister used is known as ballast resistor 




Tuesday, April 28, 2020

Dc Series Motor

Posted by Pranshu Bahuguna on April 28, 2020 No comments

Dc Series Motor

What Is Dc Series Motor?

When the armature winding is connected in series with the field winding which is energized by the dc source is Dc Series Motor.
Dc SERIES MOTOR


Working of Dc Series Motor

  • Current is same on both,series field winding and armature winding.
  • Flux produce is directly proportional to the field winding current.
Φ∝Ise


By KCL,

              Itotal=Ise=Ia
Where,
             Ise =Series Field current
             Ia   =armature current

By KVL,

              V=Eb+I(Ra+Rse)
Where,
           V=Terminal Voltage
           Eb=Back E.M.F
           I=Current
          Ra=Armature Resistance
          Rse=Series Winding Resistance.

Back E.M.F:

When the motor rotates,armature coil cut the magnetic flux,which induces an e.m.f in it known as the back e,m,f.
The back e.m.f opposes the applied voltage and always is less than applied voltage. 

                                                                    Eb=NPZΦ/60A

Characteristics Of D.C Series Motor:

  • Speed/Armature current Characteristics:

The Motor speed N in series motor is inversely proportional to the main field flux.
                                                N ∝ 1/Φ
The flux Φ is produce by the current flowing in the series field winding.Therefore flux is directly proportional to the current flowing through it.
                                                                 Φ  ∝   Ise  ∝  Ia       as  Ia = Ise
 So, the speed is inversely proportional to the armature current.
As,
The motor speed is inversely proportional to the armature current. The no load speed of motor become very high,which may damage the motor due to the centrifugal forces,because draws a small no load current.That"s why dc series motor never runs at no load or light load.

  • Torque/Armature Current Characteristics:

                                  Torque(T)=KΦI
So,
                                                T ∝ ΦIa
As,                     
                                      Φ  ∝  Ia, Before magnetic saturation
                                              T    ∝   Ia^2
After Saturation,Flux become independent of Armature current
So, 
                                     T   ∝  Ia

At Light Loads,Torque is proportional to the square of armature current.Also known as Electrical  Characteristics.

Advantages:

  • The series  motor has the highest starting torque than other Dc Motor.
  • During an overload,motor easily achieves high torque and draws less current  from the source.
  • Starting torque for the motor is high therefore it is widely used in electric traction and in crane application.

NOTE:

Static Characteristics:
Static Characteristics of an instrument are the quantity that slowly varies with the time or does not changes(remains constant).

Dynamic Characteristics:
Dynamic characteristics of an instrument are the quantity which rapidly changes with the time.









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Thursday, April 23, 2020

Dc Motor

Posted by Pranshu Bahuguna on April 23, 2020 No comments

Motor

A Electrical Machine which changes the electrical energy into mechanical energy is called Motor.
On the basis of electrical supply .They are of two types:

Dc Motor

  • Dc Motor is run by Dc Source and covert Dc electrical energy into mechanical energy.
  • When a current carrying conductor is placed on a magnetic field, it will experience a force which can be determined by Fleming's Left Hand Rule.
  • Dc Motor are subdivided into different category by changing the connection of armature winding and fielding winding.

Construction:

 Yoke:
  • The Outer Frame/Yoke is a hollow cylinder of cast iron or unlaminated  ferromagnetic material and protecting cover to the machine.
  • Yoke is stationary and no flux variation take place ,hence no iron loses. So, no need of lamination required.
  • It provides mechanical support and path for the pole flux and carry half of the magnetic field flux and other half by the armature core.                   
Field Pole:
  • Field core consist of pole core and pole shoe and made up sheet steel lamination's that are insulated from each other to reduce eddy-current losses.
  • Pole shoe are fixed to the pole core appropriately having a curved surface towards center.It supports the field coils and increase the cross section area of the magnetic circuit and reduces its reluctance.
  • Each pole has one or more field coil to produce magnetic field.
Armature:
  • It consists of a shaft upon which a laminated cylinder is mounted.The armature core has grooves or slots on its outer surface.
  • Armature conductor is located on this slots.The connected arrangement of conductors is armature winding.
  • Armature core provides the low reluctance path for the magnetic field.It is made up of thick lamination of silicon steel to reduce the eddy-current losses.





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