# Dc Machine And Transformer Pdf

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An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of torque applied on the motor's shaft. Electric motors can be powered by direct current DC sources, such as from batteries, or rectifiers , or by alternating current AC sources, such as a power grid, inverters or electrical generators. An electric generator is mechanically identical to an electric motor, but operates with a reversed flow of power, converting mechanical energy into electrical energy. Electric motors may be classified by considerations such as power source type, internal construction, application and type of motion output.

The magnetic flux in a d. The production of magnetic flux in the device by circulating current in the field winding is called excitation. There are two types of excitation in D. C machine. Separate excitation, and self-excitation. In self-excitation, the current flowing through the field winding is supplied by the machine itself, and in separate excitation, the field coils are energized by a separate D.

A list of top frequently asked Electrical Machines interview questions and answers are given below. A Single-phase autotransformer is a single winding transformer in which a part of the winding is common to both high-voltage and low-voltage sides. This law states that when we move any current carrying conductor in a magnetic field, then an EMF is induced in it. Eddy current losses can be minimized by laminating the core and insulating the core from each other with paper or varnish. High-speed alternators are called Turbo Alternators. Because of the high speed of rotation, the diameter of the rotor is reduced, and the axial length is increased.

## DC Machines and Transformers

It deals with the working, construction, and principle of DC and AC machines. These notes cover the concept of control of speed, generation of Torque, various losses, efficiency, etc. The understanding of mathematical relations between the various parameters gives an in-depth knowledge of the dependence of characteristics of these machines to optimize the output response under a given condition. DC Machines: Basic constructional features and physical principles involved in electrical machines, armature winding ac and dc , lap and wave connections, different types of pitches.

### Classifications of DC machines : (DC Motors and DC Generators)

At an armature voltage of V, the motor produces a torque of Nm at zero speed. A V DC series motor, when operating from rated voltage while driving a certain load, draws 10 A current and runs at r. The magnetic circuit is assumed to be linear. The speed of the motor in r. A V DC series motor runs drawing a current of 30 A from the supply. Armature and field circuit resistance are 0. The load torque varies as the square of the speed.

The conversion of this mechanism is known as the commutator, thus these machines are also named as commutating machines. DC machine is most frequently used for a motor. The main benefits of this machine include torque regulation as well as easy speed. The applications of the DC machine is limited to trains, mills, and mines. For example, underground subway cars, as well as trolleys, may utilize DC motors. In the past, automobiles were designed with DC dynamos for charging their batteries.

A DC Machine is an electro-mechanical energy conversion device. The AC motor is invariably applied in the industry for conversion of electrical power into mechanical power, but at the places where the wide range of speeds and good speed regulation is required, like in electric traction system, a DC motor is used. The construction of the dc motor and generator is nearly the same. The generator is employed in a very protected way. Hence there is an open construction type.

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A dc generator is an electrical machine which converts mechanical energy into direct current electricity. This energy conversion is based on the principle of production of dynamically induced emf. This article outlines basic construction and working of a DC generator. Note: Theoretically, a DC generator can be used as a DC motor without any constructional changes and vice versa is also possible. These basic constructional details are also valid for the construction of a DC motor.

Recieve free updates Via Email! Home Electrical machines Power system Ask a question Contact electricaleasy. Share: Facebook Twitter Linkedin. Each DC machine can act as a generator or a motor. Hence, this classification is valid for both: DC generators and DC motors. DC machines are usually classified on the basis of their field excitation method. This makes two broad categories of dc machines; i Separately excited and ii Self-excited.

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