Construction of dc generator pdf

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A DC Generator is an electrical device which converts mechanical energy into electrical energy. The other parts of a DC Generator are Magnetic frame and Yoke, Pole Core and Pole Shoes, Field or Exciting coils, Armature Core and Windings, Brushes, End housings, Bearings and Shafts. A dc generator is an electrical machine which converts mechanical energy into direct current figure shows the constructional details of a. University of Babylon. Electrical machines mechanical department. U Construction of DC Generators. The parts of a simple DC generator are shown in fig.

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Construction Of Dc Generator Pdf

current (dc) motor or generator, the induction motor or generator, and a number of derivatives of all these three. What is common to all the members of this fam-. This forms a simple COMMUTATOR. The commutator in a dc generator replaces the slip rings of the ac generator. This is the main difference in their construction. versa (DC motor) without any constructional changes. Thus, a DC generator or a DC motor can be broadly termed as a DC machine. II. Construction of DC.

It produces the main magnetic flux. These various parts of DC Generator are described below in detail. Magnetic Frame and Yoke The outer hollow cylindrical frame to which main poles and inter-poles are fixed and by means of which the machine is fixed to the foundation is known as Yoke. It is made of cast steel or rolled steel for the large machines and for the smaller size machine the yoke is generally made of cast iron. The two main purposes of the yoke are as follows:- It supports the pole cores and provides mechanical protection to the inner parts of the machines. It provides a low reluctance path for the magnetic flux. Since the poles, project inwards they are called salient poles. Each pole core has a curved surface. Usually, the pole core and shoes are made of thin cast steel or wrought iron laminations which are riveted together under hydraulic pressure. The poles are laminated to reduce the Eddy Current loss. The figure of pole core and pole shoe are shown below. The poles core serves the following purposes given below. It supports the field or exciting coils.

The coils are wound on the former and then placed around the pole core.

Basic construction and working of a DC Generator. |

When direct current passes through the field winding, it magnetizes the poles, which in turns produces the flux. The field coils of all the poles are connected in series in such a way that when current flows through them, the adjacent poles attain opposite polarity. The armature consists of a shaft upon which a laminated cylinder, called Amature Core is placed. Armature Core The armature core of DC Generator is cylindrical in shape and keyed to the rotating shaft.

At the outer periphery of the armature has grooves or slots which accommodate the armature winding as shown in the figure below. The armature core of a DC generator or machine serves the following purposes. It houses the conductors in the slots. It provides an easy path for the magnetic flux.


As the armature is a rotating part of the DC Generator or machine, the reversal of flux takes place in the core, hence hysteresis losses are produced. The silicon steel material is used for the construction of the core to reduce the hysteresis losses.

The rotating armature cuts the magnetic field, due to which an emf is induced in it. This emf circulates the eddy current which results in Eddy Current loss. Thus to reduce the loss the armature core is laminated with a stamping of about 0. Each lamination is insulated from the other by a coating of varnish.

Armature Winding The insulated conductors are placed in the slots of the armature core. The conductors are wedged, and bands of steel wire wound around the core and are suitably connected.

This arrangement of conductors is called Armature Winding. The armature winding is the heart of the DC Machine.

Construction of a DC Generator

Armature winding is a place where conversion of power takes place. In the case of a DC Generator here, mechanical power is converted into electrical power. On the basis of connections, the windings are classified into two types named as Lap Winding and Wave Winding. Lap Winding In lap winding, the conductors are connected in such a way that the number of parallel paths are equal to the number of poles.

In lap winding, the number of brushes is equal to the number of parallel paths. Out of which half the brushes are positive and the remaining half are negative. Wave Winding In wave winding, the conductors are so connected that they are divided into two parallel paths irrespective of the number of poles of the machine. In this case number of brushes is equal to two, i. Commutator in DC Generator The commutator, which rotates with the armature, is cylindrical in shape and is made from a number of wedge-shaped hard drawn copper bars or segments insulated from each other and from the shaft.

The segments form a ring around the shaft of the armature. Each commutator segment is connected to the ends of the armature coils. It is the most important part of a DC machine and serves the following purposes.

It connects the rotating armature conductors to the stationary external circuit through brushes. The reverse function of the generator can be done by an electric motor.

The main function of the motor is to convert electrical energy to mechanical. Motors, as well as generators, have similar features.

This article discusses an overview of DC generators. What is a DC Generator?

A DC generator or direct current generator is one kind of electrical machine, and the main function of this machine is to convert mechanical energy into DC direct current electricity. The energy alteration process uses the principle of energetically induced electromotive force. This electromotive force can cause a flow of current when the conductor circuit is not opened.

The construction of a 4-pole DC generator is shown below. But the two essential parts of this device are stator as well as the rotor. Stator The stator is an essential part of the DC generator, and the main function of this is to provide the magnetic fields where the coils spin. This includes stable magnets, where two of them are with reverse poles facing. These magnets are located to fit in the region of the rotor. Rotor or Armature Core Rotor or armature core is the second essential part of the DC generator, and it includes slotted iron laminations with slots that are stacked to shape a cylindrical armature core.

Generally, these laminations are offered to decrease the loss because of the eddy current. Armature Windings The armature core slots are mainly used for holding the armature windings.

These are in a closed circuit winding form, and it is connected in series to parallel for enhancing the sum of produced current. Yoke The external structure of the DC generator is Yoke, and it is made with cast iron otherwise steel.

It gives the necessary mechanical power for carrying the magnetic-flux given through the poles. Poles These are mainly used to hold the field windings. In addition, the poles will give joint toward the yoke with the welding method otherwise by using screws.

Pole Shoe The pole shoe is mainly utilized for spreading the magnetic flux as well as to avoid the field coil from falling. Commutator The working of the commutator is like a rectifier for changing AC voltage to the DC voltage within the armature winding to across the brushes. It is designed with a copper segment, and each copper segment is protected from each other with the help of mica sheets.

It is located on the shaft of the machine.

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