Digital Electronics Articles - Page 39 of 57

We can create a Cucumber project template using Maven. This can be done by following the below steps −Step1− Click on the File menu in Eclipse. Then select the option New. Next click on Other.Step2− Click on Maven Project from the Maven folder. Then click on Next.Step3− Proceed with the further steps.Step4− Select maven-archetype-quickstart template. Then click on Next.Step5− Add GroupId as Automation, Artifact Id as Cucumber, and proceed.Step6− A project should get created with a Cucumber-type project structure. The Cucumber-related scripts should be written within the src/test/java folder.

A synchronous motor is not inherently self-starting. Therefore, it requires some auxiliary means of starting. In order to start a synchronous motor, there are following two methods −Starting with an external prime moverStarting with damper windingsSynchronous Motor Starting with an External Prime MoverIn this method of starting a synchronous motor, an external motor is used to drive the synchronous motor as shown in Figure-1.The external motor brings the synchronous motor to synchronous speed and then the synchronous motor is synchronised with the AC supply as a synchronous generator. Then the prime mover (i.e., the external motor) is disconnected. Once synchronised, ... Read More

A motor in general is an electrical machine that converts electrical energy into mechanical energy. Electric motors can either be DC Motors or AC Motors, depending on the type of power supply that is supplied as its input.AC motors are further classified into two types−Asynchronous or Induction MotorSynchronous MotorA synchronous motor always runs at synchronous speed, while an induction motor runs at a speed less than the synchronous speed.Read through this article to find out more about synchronous motors and induction motors and how they are different from each other.What is a Synchronous Motor?A synchronous motor is a type of ... Read More

Units of Synchronizing Power Coefficient (𝑷𝐬𝐲𝐧)Generally, the synchronizing power coefficient is expressed in Watts per electrical radian, i.e., $$\mathrm{𝑃_{syn} =\frac{𝑉 𝐸_{𝑓}}{𝑋_{𝑠}}cos\:𝛿 \:\:Watts/electrical\:radian …(1)}$$$$\mathrm{∵ \:𝜋\:radians = 180\:degrees}$$$$\mathrm{\Rightarrow\:1\:radian =\frac{180}{𝜋}\:degrees}$$$$\mathrm{∵ \:𝑃_{syn}=\frac{𝑑𝑃}{𝑑𝛿}\:\:Watts/ \left(\frac{180}{𝜋}\:degrees \right)}$$$$\mathrm{\Rightarrow\:𝑃_{syn}=\left( \frac{𝑑𝑃}{𝑑𝛿}\right)\left(\frac{𝜋}{180}\right)\:\:Watt/electrical\:degree …(2)}$$If p is the total number of pole pairs in the machine, then$$\mathrm{𝜃_{electrical} = 𝑝 \cdot 𝜃_{mechanical}}$$Therefore, the synchronizing power coefficient per mechanical radian is given by, $$\mathrm{𝑃_{syn} = 𝑝 \cdot\left( \frac{𝑑𝑃}{𝑑𝛿}\right)\:\:Watts/mech. radian …(3)}$$And, the synchronizing power coefficient per mechanical degree is given by, $$\mathrm{𝑃_{syn} =\left( \frac{𝑑𝑃}{𝑑𝛿}\right)\left(\frac{𝑝\:𝜋}{180}\right)\:Watts/mech.degree …(4)}$$Significance of Synchronizing Power CoefficientThe synchronizing power coefficient ($𝑃_{syn}$) is the measure of the stiffness of the electromagnetic coupling between the stator ... Read More

When the flux density distribution in the alternator is non-sinusoidal, the induced voltage in the winding will also be non-sinusoidal. Thus, the pitch factor or coil span factor, distribution factor and winding factor will be different for each harmonic voltage.Pitch Factor for nth HarmonicAs the electrical angle is directly proportional to the number of poles and the angle between the adjacent slots, i.e., $$\mathrm{𝜃_{𝑒} =\frac{𝑃}{2}𝜃_{𝑚} … (1)}$$The chording angle increases with an increase in the order of the harmonics (n). In a short pitch coil, the chording angle is α° (electrical) for the fundamental flux wave. For the nth harmonic, ... Read More

A 1-phase supply produces a pulsating magnetic field which does not rotate in the space. Therefore, a 1-phase supply cannot produce rotation in a stationary rotor. Although, like a 3-phase supply, the 2-phase supply can also produce a rotating magnetic field of constant magnitude. Therefore, all the single-phase induction motors, except shaded pole induction motor, are started as 2-phase motor. Once so started, the motor will continue to run on the 1-phase supply.How does a 2-Phase Supply Produce Rotating Magnetic Field of Constant Magnitude?Consider a 2-phase, 2 pole motor, where the phases A and B are fed by a balanced ... Read More

Operating Principle of Single-phase Induction MotorA single-phase induction motor consists of a squirrel cage rotor and a stator carrying a single-phase winding. When a single-phase AC supply is fed to the stator winding, a pulsating magnetic field (not the rotating) is produced. Under these conditions, the rotor does not rotate due to inertia. Hence, a single-phase induction motor is inherently not self-starting, but requires some auxiliary starting means.If the stator winding of a single-phase induction motor is excited and the rotor is rotated by an auxiliary means and the starting device is then removed, the motor continues to rotate in ... Read More

The differences between a single-phase and a three-phase induction motor are given below −A 1-phase induction motor requires single-phase AC supply, whereas a 3-phase induction motor need a source of 3-phase AC supply for its operation.1-phase induction motors produce low starting torque, whereas 3phase induction motors produce high starting torque.The efficiency of a 1-phase induction motor is less as compared to a 3phase induction motor.The power factor of a 1-phase induction motor is low, while the power factor of a 3-phase induction motor is high.1-phase induction motors are simple in construction, reliable and economical as compared to 3phase induction motors.1-phase ... 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 electrical transformer is tested at the transformer manufacturer premises and at the consumer’s site and also periodically in regular and emergency basis during its service life to confirm its specifications and performance.Types of Transformer TestsTests of transformer done at the manufacturer’s premises −Type testsRoutine testsSpecial testsTests of transformer done at the consumer’s site −Pre-commissioning testsPeriodic testsEmergency testsType Tests of TransformerThe type tests of a transformer are performed at the manufacturer’s premises to prove the design expectations and consumer’s specifications. The type tests are performed in a prototype unit, not in all manufactured units and these tests confirm the basic ... Read More