Found 1006 Articles for Electronics & Electrical

The full-load iron losses and copper losses can be determined by open-circuit test and short-circuit test respectively. Therefore, From the open circuit test, $$\mathrm{Full \:load\: iron \:loss \:= \:P_{i} Watt}$$From the short-circuit test, $$\mathrm{Full \:load\: copper \:loss = P_{cu} Watt}$$$$\mathrm{\therefore\:Total\: full\: load \:losses\: = P_{i} + P_{cu} Watt}$$Therefore, the efficiency of transformer at full-load is$$\mathrm{\eta_{fl} =\frac{VI_{fi} × cos\varphi2}{(VI_{fi} × cos \varphi2) + P_{i} + P_{cu}}… (2)}$$Now, for fraction of load, i.e., if the load is x &tImes; Full load, then, $$\mathrm{Corresponding\: total \:losses = P_{i} + x^2P_{cu}}$$The iron loss (Pi) remains constant at all loads.Thus, the efficiency corresponding to fraction ... Read More

The util.promisify() method basically takes a function as an input that follows the common Node.js callback style, i.e., with a (err, value) and returns a version of the same that returns a promise instead of a callback.Syntaxutil.promisify(original)ParametersIt takes only one parameter −original −This parameter takes an input for the function and returns them as a promise.Example 1Create a file with the name "promisify.js" and copy the following code snippet. After creating the file, use the command "node promisify.js" to run this code.// util.promisify() Demo example // Importing the fs and util modules const fs = require('fs'); const util = ... Read More

An ideal transformer is an imaginary transformer which has the following characteristics −The primary and secondary windings have negligible (or zero) resistance.No leakage flux, i.e., whole of the flux is confined to the magnetic circuit.The magnetic core has infinite permeability, thus negligible mmf is require to establish flux in the core.There are no losses due winding resistances, hysteresis and eddy currents. Hence, the efficiency is 100 %.Woking of Ideal TransformerIdeal Transformer on No-LoadConsider an ideal transformer on no-load, i.e., its secondary winding is open circuited (see the figure). Thus, the primary winding is a coil of pure inductance.When an alternating ... Read More

Transformer A transformer is a static electrical machine which is used for either increasing or decreasing the voltage level of the AC supply with a corresponding decrease or increase in the current at constant frequency. Parts of a Transformer A typical transformer essentially consists of following main parts − Magnetic Core Transformer Windings Transformer Body / Tank and Dielectric Oil Oil Conservator Tank Breather Magnetic Core The core of the transformer is made up of magnetic materials having high permeability. As the transformer is subjected to the ... Read More

A practical transformer is the one which has following properties −The primary and secondary windings have finite resistance.There is a leakage flux, i.e., whole of the flux is not confined to the magnetic circuit.The magnetic core has finite permeability, thus a considerable amount of mmf is require to establish flux in the core.There are losses in the transformer due to winding resistances, hysteresis and eddy currents. Therefore, the efficiency of a practical transformer is less than 100 %.The figure shows a typical practical transformer, which possess all the characteristics that are described above.Winding ResistancesAs the windings of a transformer are ... Read More

The Ward Leonard Method of speed control is based on the fact that the speed of DC motors can be changed by varying the applied voltage to the armature. The schematic diagram of the ward-leonard method is shown in the figure.In Ward-Leonard system, M is the DC motor whose speed is to be controlled and G is a separately excited DC generator which is driven by either a 3-three phase induction motor or synchronous motor. The combination of AC driving motor and the DC generator is known as the motor-generator set or M-G set.By varying the field current of the ... Read More

A self-excited DC generator has its own field excitation. Consider a shunt generator in which the field winding is connected in parallel with the armature, thus armature voltage supplies the field current.Assume that the generator has no-load connected to it and the armature is driven at a certain speed by a prime mover. The voltage build up in a DC generator depends upon the presence of the residual flux in the field poles of the generator. Because of this residual flux, a small voltage E0r of the order of 1 V or 2 V will be generated and is given ... Read More

According to the type of connection of the field winding with the armature, the DC motors are classified as follows −Permanent Magnet DC MotorsSeparately-Excited DC MotorsSelf-Excited DC MotorsSeries Wound DC MotorShunt Wound DC MotorCompound Wound DC MotorPermanent Magnet DC MotorA DC motor in which the main field flux is produced by the permanent magnets is known as permanent magnet DC motor. In this type DC motor, there is only one external source of DC supply is required, for supplying electrical power to the armature. The permanent magnet DC motors are mainly used in small scale application like in toys.Separately-Excited DC ... Read More

In DC machines, the drum type armature windings are used. In the case of drum type winding, the armature conductors (in the form of coils) are placed in the slots around the surface of cylindrical or drum shaped armature core. The coils are connected in series through the commutator segments such that their EMFs are added to each other.In DC machines, two types of armature windings are used −Wave WindingLap WindingWave WindingIn the case of wave winding, the armature coils are connected in series through the commutator segments in such a way that the armature winding is divided into two ... Read More

The power losses which occur in a transformer are of two types −Core or Iron Losses (Pi)Copper Losses or I2R Losses (Pcu)The losses in a transformer appears in the form of heat which increases the temperature and reduces the efficiency.Core or Iron Losses (Pi)The iron losses occur in the core of the transformer due to the alternating flux. These losses consist of hysteresis loss (Ph) and eddy current loss (Pe), i.e., $$\mathrm{P_{i}=P_{h}+P_{e}}$$The hysteresis and eddy-current losses are given by, $$\mathrm{Hysteresis\:loss, \: P_{h} \:= \:k_{h}f_{max}^{1.6} \:1.6 V \:Watt}$$$$\mathrm{Eddy\:current \:loss, \:P_{e} \:= \:K_{e}f^2B_{max}^{2}t^2 V \:Watt}$$Where, kh = hysteresis coefficient, ke = eddy ... Read More