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 osakeya.info 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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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 is the most important means of producing electrical power in many of the places since now days all the consumers are using AC. It works based on principle of the electromagnetic induction. These are of two types one is induction generator and other one is synchronous generator. The induction generator requires no separate DC excitation, regulator controls, frequency control or governor. This concept takes place when conductor coils turn in a magnetic field actuating a current and a voltage.
The generators should run at a consistent speed to convey a stable AC voltage, even no load is accessible. Synchronous generators are large size generators mainly used in power plants.
These may be rotating field type or rotating armature type. In rotating armature type, armature is at rotor and field is at stator.
Rotor armature current is taken through slip rings and brushes. These are limited due to high wind losses. These are used for low power output applications. Rotating field type of alternator is widely used because of high power generation capability and absence of slip rings and brushes. It can be either 3 phase or two phase generators.
A two-phase alternator produces two completely separate voltages. Each voltage may be considered as a single-phase voltage. Each is generated voltage completely independent of the other.
These can be connected either delta or wye connections. In Delta Connection each coil end is connected together to form a closed loop. In Wye Connection one end of each coil connected together and the other end of each coil left open for external connections.
A Wye Connection appears as the letter Y. These generators are packaged with an engine or turbine to be used as a motor-generator set and used in applications like naval, oil and gas extraction, mining machinery, wind power plants etc Advantages of AC Generator: Easily step up and step down through transformers.
Transmission link size might be thinner because of step up feature Size of the generator relatively smaller than DC machine Losses are relatively less than DC machine These Generator breakers are relatively smaller than DC breakers DC Generators: DC generator is typically found in off-grid applications.
These generators give a seamless power supply directly into electric storage devices and DC power grids without novel equipment. The stored power is carries to loads through dc-ac converters. 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. 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. 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. 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.
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.
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. 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.
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.
Carbon brushes are placed or mounted on the commutator and with the help of two or more carbon brushes current is collected from the armature winding.
Each brush is supported in a metal box called a brush box or brush holder. The brushes are pressed upon the commutator and form the connecting link between the armature winding and the external circuit. The pressure exerted by the brushes on the commutator can be adjusted and is maintained at a constant value by means of springs. With the help of the brushes the current which is produced on the windings, is passed on to the commutator and then to the external circuit.