Electrical World

Introduction of VCB         A vacuum circuit breaker VCB  is such kind of circuit breaker where the arc quenching takes place in vacuum.The operation of opening and closing of current carrying contacts and associated arc interruption take place in a vacuum chamber in the breaker which is called vacuum interrupter .The vacuum interrupter consists of a steel arc chamber in the center symmetrically arranged ceramic insulators.The vacuum pressure inside a vacuum interrupter is normally maintained at (10)-6 bar.         Vacuum circuit breaker are employed for outdoor applications ranging from 22kv to 66kv, Even with limited rating say 60 to 100MVA ,they are suitable for majority of application in rural areas. Construction of VCB    It consist of fixed contact, moving contact and arc shield mounted inside a vacuum chamber. The movable member is connected to the control mechanism by stainless steel bellows.This enables t...

Basic Principle                Ac generators or alternators operate on the principles of electromagnetic induction. There is one important difference between A.C generator and D.C generator the armature rotates and the field system is stationary where as in A.C generator it is just the reverse of it.In their case standard construction consists of armature winding mounted on a stationary element called stator and field winding on a rotating element called rotor. Speed and Frequency           In an alternator there exists a definite relationship between the rotational speed (N) of the rotor the frequency (f) of the generated e.m.f and the number of poles P. P= 120f / N        It is clear from the above equation that because of slow relative speeds of engine driven alternators their number of poles is must greater as compared to that of the turbo generators which run at very high ...

Introduction        While dealing with alternating voltages and currents ,it had been assumed that they have sinusoidal waveform or shape.Such a waveform is an ideal one and much sought after by the manufactures and designers of alternators, but it is nearly impossible to realize such a waveform in practice.All the alternating waveforms deviate to a greater or lesser degree, from this ideal sinusoidal shape,Such waveforms are referred to as non-sinusoidal or distorted or complex waveforms.         The fundamental and its higher multiples form a harmonic series.Fundamental wave itself is called the first harmonic.The second harmonic has frequency twice that of fundamental,The third harmonic has frequency thrice that of the fundamental and so on. fig. Complex Waveforms           Complex waveforms are produced due to the superposition of sinusoidal waves of different frequencies.On analysis, it is found that a co...

Energy Audit Introduction         Energy audit is the first step in order to discover the possibilities of energy savings, prioritizing projects,tracking progress and making system adjustments after investments.Industrial energy audit is a process that makes saving of energy and raw materials possible.        The most common energy types measured during the auditing process are. Liquid and gas fuel flows. Electrical measurements (voltage,current,load-diagram ,power and power factor). Temperatures of solid and liquid surfaces,including surface thermography. Building infiltration and ex filtration parameters. Pressure of fluids in pipes,furnaces or vessels. Fume gas parameters(CO2,CO,O2 and PM). Relative humidity. Luminance levels.         All of the acquired data must be carefully processed and interpreted in order to obtain the most accurate result possible. Benchmarking        ...

Design of Magnetic Motor Starters and Auto -Breakers(MCCB) Fig.1 Fig.2          For Design of Magnetic Motor Starters and Auto - Breakers one can select the voltage ,Phase and frequency from fig1 and pick the different values from fig2 (Column-wise) according to the HP or KW of any motor

 It a method by adopding one can designe the power factor improvement panel for any industry if he knows the load and the respective power factor of the devices.  For further help plz, mention the query in comment section.

Selection of Magnetic Motor Starters an FUJI Auto -Breakers(MCCB) Fig.1 Fig,2    For design a DOL Starter pick the values according to voltage ,Phase and frequency from fig.1  and see the corresponding values in column wise from fig.2 according to the HP or KW of any motor.

Introduction        Electrical grounding originally began as a safety measure used to help prevent people from accidentally coming in contact with electrical hazards.         For measurement purposes, the earth serves as a contact potential reference against which other potentials can be measured. An electrical ground system should have an appropriate current carrying capability to serve as an zero voltage reference level. Where a real ground connection has a significant resistance the approximation of zero potential is no longer valid.          Ideally a ground should be of zero ohm resistance.There is not one standard ground resistance threshold that is recognized by all agencies.However the NFPA and IEEE have recommended a ground resistance value of 5 ohm or less. Importance of Ground for a Generator        Generator system must have proper grounding of all electrical components and tr...

Introduction               A transformer is a static electrical machine which transfers AC electrical power from one circuit to the other circuit at the constant frequency, but the voltage level can be altered that means voltage can be increased or decreased according to the requirement. Working Principle        The working principle of transformer is very simple, Mutual inductions between two or more windings is responsible for transformation action in an electrical transformer.                         Basic Theory of Transformer        Say you have one winding which is supplied by an alternating electrical source. The alternating current through the winding produces a continually changing flux or alternating flux that surrounds the winding. If any other winding is brought nearer to the previous one, obviously some portion of...

 A three Phase induction motor is self starting.When the supply is connected to the stator of a three-phase induction motor, rotating magnetic field is produced.and the rotor starts rotating and the induction motor starts.At the time of starting the starting current is very high.Due to this high  current, we need some soft start for motor. Soft Starter           A motor soft starter is a device used with Ac electrical motors to temporarily reduce the load and torque in the power train and electric current surge of the motor during start up.          Motor often require large amounts of energy when quickly accelerating to full speed. Soft starters and variable frequency drives can both be used to reduce inrush current and limit torque protecting equipment and extending the life of a motor by reducing motor heating caused by frequent starts and stops.But there are a number of differences between a soft starter and a varia...

Definition                     An alternating current motor in which torque is produced by the reaction between a varying field generated in the stator and the current induced in the coils of the rotor.   Principle of Induction Motor                                     Induction motor works on the principle of induction where electro-magnetic field is induced into the rotor when rotating magnetic field of stator cuts the stationary rotor.                       Types of Induction Motor         Single Phase Induction Motor              The single phase induction motors are made self starting by providing an additional flux by some additional means.Now depending upon the additional means the single phase ind...

Introduction                                          Air circuit breaker (ACB) is an electrical device used to provide over current and short circuit protection for electrical circuits over 800 Amps to 10k Amps.These are usually used in low voltage applications below 450v. Types of Air Circuit Breakers               There are mainly two types of Air circuit breakers are available . Plain air circuit breaker or cross blast circuit breaker. Air blast circuit breaker.            Air blast circuit breaker is further sub divided . Axial blast breaker Axial blast with sliding contactor Major Components of ACB                The major components of Air circuit breaker are poles, The arc chuts, The base frame the operating mechanism. Poles     ...