Types of dc motor

Types of dc motor

     D.c motors are classified depending upon the way of connecting the field winding with the armature winding. The different types of d.c motors are

              

1. Shunt motor

2.Series motor

3. compound motors

The compound motors are further classified as 

        

1. Short shunt compound motors

2. Long shunt compound motors 

compound generator

compound generator 

     In this type, the part of the field winding is connected in parallel with armature and part in series with the armature. Both series and shunt field winding are mounted on the same poles. Depending upon the connection of shunt and series field winding compound generator is further classified as .

       

     1. Long shunt compound generator 

     2. Short shunt compound generator 

1. Long shunt compound generator

     In this type, shunt field winding is connected across the series combination of armature and series field winding as shown in the picture.

2. Short shunt compound generator 

     In this type, shunt field winding is connected, only across the armature excluding series field winding as shown in the below picture

Series Generator

Series Generator 

     When the field winding is connected in series with the armature winding while supplying the load then the generator is called series generator. It is shown the picture.

     Field winding in this case is denoted as S1 and S2. The resistance of series field winding is very small and hence naturally it has less number of turns of thick cross-section wire as shown in the picture. Let Rse be the resistance of the series field winding.

     

Shunt Generator

Shunt Generator 

     When  the field winding is connected in parallel with the armature and the combination across the  load then the generator is called shunt generator .

     

     The field winding has large number of turns of thin wire so it has high resistances. Let Rsh be the resistance of the field winding .

Self Excited Generator

Self Excited Generator 

      When the field winding is supplied from the armature of the generator itself then it is said to be self excited generator. Now without generated e.m.f., field cannot be excited in such generator and without excitation there cannot be generated e.m.f. So one may obviously wonder, how this type of generator works. The answer to this is residual magnetism possessed by the field poles, under normal condition.

      Practically though the generator is not working, without any current through field winding, the field poles possess some magnetic flux. This is called  residual flux and the property is called residual magnetism. Thus when the generator is started due to such residual flux, it develops a small e.m.f. which now drives a small current through the field winding. This tends to increase the flux produced. This in turn increases the induced e.m.f.

This further increases the field current and the flux. The process is cumulative and continues till the generator develops rated voltage across its armature. This is voltage

building process in self excited generators.

      Based on how field winding is connected to the armature to derive its excitation, this

type is further divided into following three types.

i) Shunt generator

ii) Series generator

iii) Compound generator

What is current

Define Current

CURRENT (I)

     The flow of free electrons in any conductor is called current. it is denoted by the letter (I) . the unit of current is ampere. One ampere can be defined as the motion of electric charge at the rate of one coulomb per second.

Symbol   =  I

Si Unit    = ampere

Ampere  =  (A)

Electrical potential

ELECTRIC POTENTIAL

Electrical Potential

     When a body is charged, work is done in charging it this work done is stored in the body in the form of potential energy. The charged body has the capacity to do work by moving other charges. The ability or capacity of a charged body to do work is called electric potential. unit of electric potential is volt.

Electric potential( v ) = work done /charge

                               = w/q

What is the SI Unit of power

What is the SI Unit of power

Power

    

     The dimension of power is energy divided by Time.

                 Symbol  =      P

                 Si Unit   =       Watts 

    

         Watt symbol   =       W

                 1 Watt   =       1 Joule per second 

Define ohm's law

What is ohm's law

Ohm's law

       Ohms law states that at constant temperature the current flow through a conductor is directly proportional to the potential difference between the two ends of the conductor . 

What is Torque Define Torque

What is Torque 

Torque 

     

Torque is the twisting moment or turning moment of a circulating body. The unit of torque is Newton-metre. When a force of one Newton acts on a pulley of one metre radius the torque developed is one Newton-meter. 1kg.m = 9.8 NM

what is thermal energy or heat energy

What is thermal energy or heat energy

Thermal energy

   

     Calorie is the unit of heat energy.One calorie is defined as the amount of heat required to raise the temperature of one gram of water through one degree centigrade.

Heat energy H = MST calories

where 

       M = Mass of the body in gm

       S = Specific heat of the body

       t = Change of temperature

1 calorie = 4. 86 Joules

what is emf Define emf

What is EMF

    It is the force which causes to flow the electrons in any closed circuit. the unit of electromotive force is volt.

One volt is defined as the p.d across a resistance of one ohm carrying a current of one ampere.

What is the unit of work what is the si unit of work

What is the unit of work

Work

   

   Common symbol =  W

   

   SI Unit                 = Joule (J)

What is the unit of energy what is the si unit of energy

What is the unit of energy 

Unit of energy = Joules 

   1 Joule (J) is the MKS unit of energy, equal to the force of one Newton acting through one meter

what is energy

what is energy

Energy (E)

     

     Energy is the capacity to do work. The unit of electrical energy is walt sec.or joules.

Energy = power X time = P xt

Unit of energy = Joules 

 1 Joule (J) is the MKS unit of energy, equal to the force of one Newton acting through one meter

what is mechanical energy define mechanical energy

what is mechanical energy define mechanical energy 

Energy (E)

    

     Joule is the unit of mechanical energy joules is defined as the work done,when a force of one Newton moves through a distance of one metre.

         One joule = One watt sec 

What is work define work

What is work define work 

Work

      Work is said to be done on a body. When a force acts on it, the body through some distance. The unit of work is joule or Newton-metre.

Work =  Force X distance

Explain Separately excited generator

Separately excited generator

     When the field winding is supplied from external separate d.c supply i.e excitation of field winding is separate then the generator is called separately excited generator .

     The field winding of this types of generator has large number of turns of thin wire. So length of such winding is more with less cross-sectional area. So resistance of this field winding is high in order to limit the field current .

Fleming's right hand rule

Fleming's right hand rule

Fleming's Right Hand Rule

     

     If three fingers of a right hand namely thumb, index finger and middle finger are outstretched so that everyone of them is at right angles with the remaining two and if in this position index finger is made to point in the direction of lines of flux, thumb in the direction of the relative motion of the conductor with respect to flux then the outstretched middle finger gives the direction of the e.m.f  induced in the conductor .

What is armature winding

What is armature winding 

 Armature winding

    An arrangement of conductors to form a winding in which e.m.f. is induced .This is called an armature winding .

 

What is field winding

What is field winding 

Field winding 

     An arrangement of winding which is used as a primary source of flux when current is passed through it. This is called field winding or exciting winding .

Faraday's Law of electro magnitic Induction

Faraday's Law of Induction 

Law of Electromagnetism

     A law stating that when the magnetic flux linking a circuit changes, an electromotive force is induced in the circuit proportional to the rate of change of the flux linkage.

        d0

e =  -----

         dt

types of LDB

types of LDB

types

         LDB  - Lighting Distribution Board

          MLDB  - Main Lighting Distribution Board

           SLDB  -  Secondary Lighting Distribution Board

 

           ELDB  -  Emergency Lighting Distribution Board

What is the full meaning of VFD

What is the full meaning of VFD

VFD - Variable Frequency Drive

What is the use of DO fuse

What is the use of DO fuse 

DO fuse or Fuse cut out

     In electrical distribution, a fuse cutout or cut-out fuse is a combination of a fuse and a switch, used in primary overhead feeder lines and taps to protect distribution transformers from current surges and overloads. An overcurrent caused by a fault in the transformer or customer circuit will cause the fuse to melt, disconnecting the transformer from the line.

abbreviation of DO Fuse

Abbreviation of DO Fuse

DO Fuse   - Drop Out Fuse

what is the full meaning of HT and LT

what is the full meaning of HT and LT

Full form of HT & LT

  '

        HT  - High Tension 

        LT  - Low Tension

        

        EHT -  Extra High Voltage

Tension is the French Language and the equivalent English translation is Voltage

LT - Low Tension ( Low Voltage )

        

Low tension lines have low voltage less than 1000 volts and high current distribution system Example of 440V 3 phase supply and 230v Single phase supply.commonly we used LT  in Secondary distribution system like our household applications are working in LT. It is used to transmit power at very small distances and use thicker conductor.

 ( P= VX I ) 

Here Low voltage and higher current , conductor size depending up on current.

HT - High Tension ( High voltage )

  

High Tension lines are using higher voltages ( 11kV, 33kV, )  it is used to Distribute power to large distances by in creasing voltage and decreasing current so as to reduce I^2 R losses. HT line uses thinner conductors than LT  line conductor.

EHV - Extra High Voltage 

Extra High voltages are using much higher voltages ( above 33 kV to 700 kV )  It is used in Transmission system to transmit higher power.

         

      

what is the full meaning of ACVS

what is the full meaning of ACVS

Abbreviation of ACVS

    

      ACVS - Air Conditioning and Ventilation System

What is the full meaning of AB Switch

What is the full meaning of AB Switch

Abbreviation of AB Switch 

        

      AB Switch - Air Break Switch

Image 

 

Explain AB Switch

Explain AB Switch 

    AB switch  - Air Break Switch

Construction 

  The Air break Switch  have triple pole construction and will be suitable for Vertical / Horizontal mounting. Each pole consist of galvanized steel base, insulators of reputed make, copper alloy male and female contacts, arcing horns of adequate section to break magnetizing current of transformer. M.S. square coupling rod of adequate length for rocking operation, required length of G.I pipe for operation from ground level and operating handle is specially design for smooth operation. Adjustable pins are provided to limit over travel of moving post. Ferric parts are hot dip galvanized and non-ferric parts are heavily tinned to withstand weather. Jumper is of EC grade braided tin plated copper of appropriate size to complete the current path from moving post to fix post.

what are the types of relay

  Types of relay

Types 

        1.       Latching relay

        2.       Reed relay

        3.       Mercury Wetted relay

        4.       Mercury relay

        5.       Polarized relay

        6.       Machine tools relay

        7.       Coaxial relay

        8.       Time delay relay

        9.       Solid state relay

       10.   Solid state contactor relay

       11.   Buchholz relay