Directional Static Overcurrent Relay: For obvious reasons of obtaining selectivity overcurrent relays are made directional. Directional static overcurrent relay senses direction of power flo… Read More

What is Summation Transformer? Summation devices are employed to compare the relaying quantities derived from the currents in the three phases of the primary circuit. The effectiveness of th… Read More

Difference between Static Relays and Electromagnetic Relays: The conventional electromagnetic relays are robust and quite reliable, but are required to operate under different forces under f… Read More

Powder Coating Process: Powder coating process is one of the most durable finishes that can be applied to industrial manufactured products, and offers excellent corrosion protection and is v… Read More

Zero Sequence Current Relay: This type of zero sequence current relay is similar to that of negative phase sequence relay as discussed in article Induction Type Negative Phase Sequence Relay… Read More

Induction Type Negative Phase Sequence Relay: This type of induction type negative phase sequence relay has similar construction as that of an induction type overcurrent relay. The differenc… Read More

Negative Phase Sequence Relay: A negative phase sequence relay (or phase unbalance) is essentially provided for the protection of generators and motors against unbalanced loading that may ar… Read More

Voltage Balance Differential Relay: In this voltage balance differential relay arrangement, two similar current transformers are connected at either end of the system element under protectio… Read More

Mho Type Distance Relay – Working and Characteristics: Mho relay is a high speed relay and is also known as admittance relay. It is also sometimes called an angle impedance relay. In t… Read More

Universal Relay Torque Equation Derivation: Universal Relay Torque Equation – Most of the protection relays consist of some arrangement of electromagnets. These electromagnets have eit… Read More

Thermal Relay Construction and Working Principle: Thermal Relay can operate on the principle of thermal effect of electric current. It consists of bimetallic strips which are used in small s… Read More

Permanent Magnet Moving Coil Relay: The arrangement of permanent magnet moving coil relay is shown in Fig. 9.12. In this relay, the coil is free to rotate in the magnetic field of a permanen… Read More

Electromagnetic Induction Relay – Structure and Working Principle: Electromagnetic induction relay operate on the principle of induction motor and are widely used for protective relayi… Read More

Classification of Relays: The protective relay may be defined as an electrical device interposed between the main circuit and the circuit breaker in such a manner that any abnormality in the… Read More

Types of Circuit Breaker Mounting: There are four types of circuit breaker mounting, which are described below: Cubicle Type or Cellular Type: In this type of mountings the circuit breakers… Read More

HVDC Circuit Breakers – Construction and Working Principle: Light duty dc circuit breakers have been in use since long. However, there is lack of suitable circuit breakers for HVDC sys… Read More

Difference between Fuse and Circuit Breaker: The difference between fuse and circuit breaker is given in table below S. No. Particulars Fuse Circuit Breaker 1 Functions It performs both of f… Read More

Factors to be Considered in Selection of Fuse: In order to ensure that the fuses will correctly and reliably protect any given section or element of an electrical circuit, selection of fuse… Read More

Instrument Transformers – Definition, Types and Errors: AC type protective relays are actuated by current and voltage supplied by current and potential (or voltage) transformers, known… Read More

Overlapping Zones of Protection: Overlapping Zones of Protection – In order to provide selectivity to the system it is usual practice to divide the entire system into several protectio… Read More

Basic Requirements of Protection System: Protection system is an extremely important part of the power system as it is provided to operate under abnormal conditions to prevent failure or iso… Read More

Why we need for Power System Protection? Need for power system protection are growing fast with more generators, transformers and large network in the systems. For system operation a high de… Read More

Sources of Fault Power: The sources of fault power originate in all the generating and other connected plants which under normal operating conditions draw power from the system. Mainly there… Read More

Effects of Short Circuit Faults on Power System: Depending upon power circuit voltage and configuration, method of neutral connection, presence of regulating devices and the speed of disconn… Read More

What is Short Circuit Current? – Definition and its Process: Whenever a short circuit current occurs in a power network, it causes heavy current to flow in the network. Figure 1.1 show… Read More

Different Types of Faults in Power System: A fault in an electrical equipment/apparatus is defined as a defect in the electrical circuit due to which current is diverted from the intended pa… Read More

General Characteristics of Electrical Equipment: All electrical machines, apparatus and other forms of characteristics of electrical equipment must satisfy two main requirements—t… Read More

Methods of Ventilation and Cooling of Electrical Machines: It is necessary to provide suitable ventilation and cooling of electrical machines so that the temperature rise at any part of the… Read More

Types of Power Transmission Drives: Mechanical power available at the motor shaft has to be transmitted to the driven machine or machines. Various types of power transmission drives are name… Read More

What is Bearing? – Definition and Types of Bearings: Bearings are those parts of a machine which house supports and restrain the rotating parts. The moving part of the bearing is known… Read More

Types of Motor Enclosures: In order to protect machines against the ingress of dirt and dust or larger foreign bodies like spanners, vermin etc. into it, it is desirable that some suitable e… Read More

Electrical Braking of Polyphase Induction Motors: Electrical Braking of Polyphase Induction Motors which consists of different types, namely, Plugging (or Counter-Current Braking) Dynamic (o… Read More

Speed Control of AC Commutator Motors: Speed control of ac commutator motors can be had either by varying the applied voltage or by movement of the brushes round the commutator. The former m… Read More

Speed Control of Single Phase Induction Motor: The stator winding of a speed control of single phase induction motor can easily be arranged to give two synchronous speeds, one double the oth… Read More

Speed Control of Three Phase Induction Motor: The problem of speed control of three phase induction motor in particular is of great practical importance. In a number of industries motors mus… Read More

Constant Current System for Speed Control of DC Motor: For certain services, where there is a possibility of the motors being stalled such as with excavators, ship’s windlasses etc. th… Read More

Booster Speed Control of DC Motor: A booster in series with the armature of the main motor may be employed for varying the voltage across the driving motor. The booster speed control is a se… Read More

Armature Resistance Control Method of DC Motor: In this armature resistance control method of speed control, reduced speeds are obtained by inserting resistance in the armature circuit. It m… Read More

Paralleling Field Coils for DC Series Motor: In this Paralleling Field Coils method, used in fan motors, several speeds can be obtained by regrouping of field coils, as illustrated in Fig. 1… Read More

Tapped Field Control for DC Series Motors: Tapped field control for dc series motors is another method of increasing the speed by reducing the flux and it is accomplished by reducing the num… Read More

Field Diverter Method of Speed Control of DC Series Motors: The field flux can be reduced by shunting a portion of motor current around the series field, thus reducing the excitation mmf and… Read More

Starting of Synchronous Motor and Precautions: As already stated the synchronous motor has got no self starting torque and the motor must first be brought up to synchronous speed by some ext… Read More

Star Delta Starter Working Principle and Circuit Diagram: This star delta starter method of starting of cage induction motors is based upon the principle that with 3 windings connected… Read More

Auto Transformer Starter – Working Principle, Advantages and Disadvantages: In auto transformer starter method the reduced voltage is obtained by taking tappings at suitable points fro… Read More

Primary Resistance Starter – Operation, Wiring Diagram, Advantages and Disadvantages: This method of primary resistance starter of a polyphase cage motor is very simple and provides sm… Read More

Starting of Squirrel Cage Induction Motor: Direct-on-Line Starting or Full-Voltage Starting – As already mentioned, squirrel-cage induction motors, as a general rule, up to 4 or 5 kW a… Read More

Starting of Slip Ring Induction Motor: The starting of slip ring induction motor is given below, At start, speed of motor is zero and, therefore, slip s = 1.0. Substituting s = 1.0 in Eqs. (… Read More

Counter Emf Automatic Starter – Working Principle and its Drawbacks: This type of starter depends upon the build up of the back or counter emf to operate the contactors (a heavy duty r… Read More

Drum Controller for DC Series Motor: DC series motors are often employed on cranes, elevators, tramcars and other applications, where the motor is under the direct control of an operator. In… Read More

DC Series Motor Starter Working Principle: The series motor starter serves the same purpose as the three- and four-point starters employed with shunt and compound wound motors. However, seri… Read More

3 Point Starter and 4 Point Starter -Construction and its Workings: The starter for a shunt motor (3 point starter) is shown in Fig. 1.59. At start all resistances are in series with the arm… Read More

Starting of Electric Drives: The most important processes associated with controlled electric drives are (i) starting, (ii) speed control (iii) braking, (iv) reversal of direction of rotatio… Read More

Repulsion Induction Motor – Construction, Working Principle and Applications: The repulsion induction motor has a single phase stator winding, as a repulsion-start induction motor has… Read More

Repulsion Start Induction Motor – Working Principle: As the name implies, the repulsion-start induction motor starts as a repulsion motor and runs as an induction motor. The general co… Read More

Compensated Repulsion Motor – Construction and Working Principle: Compensated Repulsion Motor is a modified form of the repulsion motor. It is provided with an additional winding, call… Read More

Repulsion Motor – Construction, Working Principle and Applications: The characteristics of repulsion motors are similar to those of a series motor, i.e., high start­ing torque and… Read More

Universal Motor – Construction, Working Principle and Applications: A universal motor is a specifically designed series wound motor, that operates at approximately the same speed and o… Read More

Permanent Capacitor Single Phase Induction Motor: Permanent capacitor single phase induction motor, also sometimes called the single-value capacitor—run motor, has two stator windings… Read More

Capacitor-Start Capacitor-Run Single Phase Induction Motor: The capacitor-start capacitor-run motor is similar to capacitor-start, induction-run motor, except that the auxiliary winding and… Read More

Resistance Start Single Phase Induction Motor: It is a form of split-phase motor having a high resistance connected in series with the auxiliary or starting winding, as illustrated in Fig. 1… Read More

Three Phase AC Shunt Commutator Motor: The connection diagram of a three phase ac shunt commutator motor is shown in Fig. 1.37. In this motor, the stator is connected directly to the supply… Read More

Three Phase AC Series Commutator Motor: This machine has a 3-phase stator winding similar to that of an ordinary induction motor and may be wound for high voltage if required. The rotor carr… Read More

Compensated Induction Motor (No-Lag Type Motor): This is an improve­ment of the plain induction motor designed to operate at approximately unity or slightly leading power factor over the… Read More

Schrage Motor – Connection Diagram, Advantages, Disadvantages and Applications: Variable Speed Commutator Type 3-Phase Induction Motor (Schrage Motor). This is also an improvement of t… Read More

Electric Motor Speed Torque Characteristics: A Electric motor speed torque characteristics is defined as the relationship between the speed at which it operates and the torque it develops, … Read More

Selection of Electric Drive: For selection of electric drive motor it is essential that the conditions of service are well known. It is not sufficient to simply specify the output power in k… Read More

Types of Electric Drives: The various types of electric drives used in industry may be divided into three types, namely Group Drive, Individual Drive and Multi-motor drives. 1. Group Drive:… Read More

Nature of Electric Supply: The nature of electric supply available may be 3-phase ac, single-phase ac or dc. In case three-phase ac supply is available, polyphase induction motor, squirrel c… Read More

Factors Governing Selection of Electric Motors: Parallel to the growth of machine tools, an equally rapid progress has been made in the field of electric motors. The electric motors of vario… Read More

Difference between Converter Fed and Chopper Fed DC Drives: Difference between Converter Fed and Chopper Fed DC Drives – For speed control of a dc motor it is necessary that it is supp… Read More

Special Features of Thyristor Drive Motors: The most commonly used dc motors for thyristor drive are separately excited and series excited dc motors. The thyristor drive motors usually diffe… Read More

Speed Control of DC Motor using Feedback Loop: An open-loop system can be converted into a closed-loop system by employing a speed control of dc motor using feedback loop, as illustrated in… Read More

Electric Braking of Separately Excited DC Motor: The electric braking of separately excited dc motor is show in Figure 3.31. Figure 3.31 (a) illustrates a simplified representation of a sing… Read More

Thyristor Control of 3 Phase Synchronous Motor: The synchronous motor is a constant speed motor and it devel­ops torque only at synchronous speed which is directly proportional to supply… Read More

Speed Control of Single Phase Induction Motor using Triac (Fan Regulator): The conventional speed regulator for a fan uses a resistance regulator. The regulator resistance is in series with… Read More

Protective Devices and Interlocks: Protective devices must be incorporated in the control circuit (or circuits) to interrupt the flow of current to the motor to guard against overloads or ot… Read More

Electromagnetic Relay – Definition, Construction and Working Principle: Electromagnetic Relay – A relay, in the general sense of the word, is any apparatus which serves to actuat… Read More

Magnetic Contactor – Definition, Working Principle and Types: Magnetic Contactor is a electromagnetically operated switches that provide a safe and convenient means for repeatedly maki… Read More

Various Pilot Devices in Motor Control: Motor control devices may be classified as primary control devices and pilot control devices. Pilot devices control the primary control devices which… Read More

Magnetic Amplifier – Working Principle and Applications: In a magnetic amplifier, the basic component is a steel-cored coil with an additional winding energized by direct current. It i… Read More

Amplidyne (Rotary Amplifier) – Definition, Construction, Connection Diagram, Workings and Applications: The amplidyne is a rotary amplifier in which a small amount of power supplied to… Read More

Ignitron Working Principle: Ignitron is a gaseous tube and consists of carbon anode, boron carbide ignitor tube and mercury pool cathode. It is a cold cathode tube and does not have any heat… Read More

Dielectric Heating – Working, Advantages and Applications: When non-metallic parts such as wood, plastics, bones are subjected to an alternating electrostatic field dielectric loss occ… Read More

High Frequency Power Supply Working Principle: The high frequency power supply for coreless induction furnace is usually obtained from ordinary supply system and its frequency is converted t… Read More

High Frequency Eddy Current Heating – Working, Advantages and Applications: The articles to be heated are placed within a high frequency current carrying coil, alternating magnetic fie… Read More

Induction Furnace – Definition, Types, Working Principle and Advantages: In induction heating effect of currents induced by electromagnetic action in the charge is employed. The heat d… Read More

Arc Furnace – Definition, Types, Advantages and Application: When a high voltage is applied across an air gap, the air in the gap gets ionised under the influence of electrostatic forc… Read More

Resistance Heating – Types, Advantages and Applications: Resistance heating is based upon the I2R effect. This method of heating has wide applica­tions such as heat treatment of me… Read More

Different Types of Electric Heating: Different types of electric heating can be broadly classified as (i) power frequency heating and (ii) high frequency heating. Power frequency heating can… Read More

Three Modes of Heat Transfer (Conduction, Convection, Radiation): A heated substance will give off heat to another substance at a lower temperature. The three different modes of heat transfe… Read More

What is Electric Heating and its Advantages? Heating is required for domestic purposes such as cooking and heating of buildings, as well as for industrial purposes such as melting of metals… Read More

Power Supply for Electrolytic Process: Power Supply for Electrolytic Process is direct current and at very low voltage. The power required for electrodeposition is usually very small (betwee… Read More

What is Electropolishing, Electrotyping, Electrofacing, Electrometallisation and Anodizing Closely allied to bright dipping is electropolishing, which utilises anodic treatment in specially… Read More

What is Electroforming Process? – Definition and Applications Reproduction of objects by electrodeposition on some sort of a mould or form is known as electroforming. This is another a… Read More

What is Electroplating in Electrolysis and its Working Principle Electroplating is an art of depositing a superior or a more noble metal on an inferior or a base metal by means of electrolys… Read More

Electrodeposition – Definition, Factors, Application and Advantages: The process of depositing a coating of one metal over an other metal or non-metal electrically is called the electr… Read More

Production of Chemicals by Electrolysis: There are various industrial applications of Production of Chemicals by Electrolysis such as production of caustic soda, chlorine, potassium permanga… Read More

Refining of Metals by Electrolysis: Refining is the process whereby a highly concentrated mixture of metals is subjected to electrochemical treatment for recovering not only the principal me… Read More

Extraction of Metals using Electrolysis – Zinc and Aluminium: Extraction of metals is an electrochemical process used for the production of metal with commercially acceptable purity. T… Read More

Faraday’s Laws of Electrolysis – First and Second Law: The laws governing the electrolytic processes were formulated by Michael Faraday, an English Scientist, and are known as Fa… Read More