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Energy Conversion - DC Generator

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iluv nature

on 18 March 2015

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Transcript of Energy Conversion - DC Generator

1. Series wound generators 2. Shunt wound generators






3. Compound wound generators
a. Short Shunt Compound Wound DC Generator b. Long Shunt Compound Wound DC Generator
Generally DC generators are classified according to the ways of excitation of their fields. There are three methods of excitation:
1. Permanent Magnet DC Generator 2. Separately Excited DC Generator







3. Self-excited DC Generators
B A C K G R O U N D
CHAPTER 1:
BRIEF HISTORY AND Its Background
CLASSIFICATIONS
APPLICATIONS
FUNCTIONS AND USES
1. DC shunt Generator
The terminal voltage of DC shunt generator is more or less constant from no load to full load .Therefore these generators are used where constant voltage is required.
- For electro plating
- Battery charging
- For excitation of Alternators.

2. Series Generators:
The terminal voltage of series generator increases with load current from no load to full load. Therefore these generators are,
- Used as Boosters
- Used for supply to arc Lamps
According to the position of the field coils
ENERGY CONVERSION
Direct Current Generators
DC Generator
- a rotating electric machine which delivers a unidirectional voltage and current.
Before the connection between magnetism and electricity was discovered, generators used electrostatic principles. The Wimshurst machine used electrostatic induction or "influence". The Van de Graaff generator uses either of two mechanisms:
1. Charge transferred from a high-voltage electrode
2. Charge created by the triboelectric effect using the separation of two insulators (the belt leaving the lower pulley) Electrostatic generators are inefficient and are useful only for scientific experiments requiring high voltages.
CHAPTER 1:
BRIEF HISTORY AND Its Background
HISTORIC DEVELOPMENTS
1.) Faraday
The generator is based on the principle of electromagnetic induction discovered in 1831 by Michael Faraday.
2.) Dynamo
generator in use in the 21st century. The dynamo uses electromagnetic principles to convert mechanical rotation into an alternating electric current. It is the most common way to generate electrical energy for bicycle lighting.
3.) Jedlik's dynamo
4.) Gramme dynamo
Because commutators are complex and costly, many DC generators are being replaced by AC generators combined with electronic rectifiers. Rectifiers are devices that let current flow in one direction only. They permit use of simpler, more rugged AC generators, even when DC is required.
FUTURE OF DC GENERATOR
CHAPTER 2:
CLASSIFICATIONS OF DC GENERATORS
CHAPTER 2:
CLASSIFICATIONS OF DC GENERATORS
CHAPTER 4: FUNCTIONS AND USES
CHAPTER 4: FUNCTIONS AND USES
CHAPTER 5:
DC GENERATOR OPERATION
HOW DC GENERATOR WORKS?
CHAPTER 3:
PARTS AND FUNCTIONS
PARTS AND FUNCTIONS
CHAPTER 5:
DC GENERATOR OPERATION
HOW DC GENERATOR WORKS?
1. Electroplating
2. Battery charging
3. Booster
4. Supply for Arc Lamps
6. Voltage drop
in feeders
7. Supply DC
welding machines
5. Supply for
Lodges
8. Supply Source to DC Motors with controlled speed
chapter 7: Summary
Summary
DC Generators power very large electric motor, such as those needed for subway systems, moreover, DC generators provide a reliable and efficient energy supply that can charge banks of batteries used for mobile and off-grid uses.
While AC Generators power small motors and common electrical appliances. These include vacuum cleaners, food mixers, juicers and electrical fixtures.
chapter 8:
PRESENTERS
PRESENTED BY:
Bermillo, Marvin C.
Cantonjos, Homer R.
Cruz, Hector
Cunanan, Jenny U.
Lapira, Peter
In 1827, Anyos Jedlik started experimenting with electromagnetic rotating devices which he called electromagnetic self-rotors. In the prototype of the single-pole electric starter both the stationary and the revolving parts were electromagnetic. In essence the concept is that instead of permanent magnets, two electromagnets opposite to each other induce the magnetic field around the rotor.
Both of these designs suffered from a similar problem: they induced "spikes" of current followed by none at all. Antonio Pacinotti, an Italian scientist, fixed this by replacing the spinning coil with a toroidal one, which he created by wrapping an iron ring. This meant that some part of the coil was continually passing by the magnets, smoothing out the current. Zénobe Gramme reinvented this design a few years later when designing the first commercial power plants, which operated in Paris in the 1870s. His design is now known as the Gramme dynamo. Various versions and improvements have been made since then, but the basic concept of a spinning endless loop of wire remains at the heart of all modern dynamos.
chapter 6:
COMPARISON BETWEEN
DC AND AC GENERATORS
Design Differences
-Both AC and DC generators produce currents via electromagnetic induction. In AC generators, the coil through which the current flows is fixed, and the magnet is moving. The magnet's north and south poles cause the current to flow in opposite directions, producing an alternating current.
-With DC generators, the coil through which the current flows rotates in a fixed field. The two ends of the coil attach to a commutator: different halves of a single, rotating split ring. Metal brushes connect these split rings to an external circuit. The commutator balances the charges leaving and returning to the generator, resulting in a current that does not change direction.

Primary Uses of AC and DC Generators
- AC and DC generators serve different purposes. Homes typically use AC generators to power small motors and common electrical appliances. These include vacuum cleaners, food mixers, juicers and electrical fixtures.
- DC generators power very large electric motors --- such as those needed for subway systems. Moreover, DC generators provide a reliable and efficient energy supply that can charge banks of batteries used for mobile and off-grid uses.
chapter 6:
COMPARISON BETWEEN
DC AND AC GENERATORS
Safety, Sizing and System Connectivity
-AC generators are typically 120 volts and higher and require safety certifications; these currents can cause injury or death. Low voltage (less than 50) DC generators require nominal inspections and permits.

-The design of an AC generator must account for all possible loads, even when powering small loads for most of the time. In contrast, DC generators can charge smaller batteries and still provide a steady current.

-While AC generators require much engineering and incur high costs to transfer electricity to isolated sections of the grid, the design of a DC system does not require a transfer switch. This allows for seamless and efficient power flow.
1. Rotor
-In its simplest form, the rotor consists of a single loop of wire made to rotate within a magnetic field. In practice, the rotor usually consists of several coils of wire wound on an armature.
2. Armature
-The armature is a cylinder of laminated iron mounted on an axle. The axle is carried in bearings mounted in the external structure of the generator. Torque is applied to the axle to make the rotor spin.
3. Coil
-Each coil usually consists of many turns of copper wire wound on the armature. The two ends of each coil are connected either to two slip rings (AC) or two opposite bars of a split-ring commutator (DC).
CHAPTER 3:
PARTS AND FUNCTIONS
4. Stator
-The stator is the fixed part of the generator that supplies the magnetic field in which the coils rotate. It may consist of two permanent magnets with opposite poles facing and shaped to fit around the rotor. Alternatively, the magnetic field may be provided by two electromagnets.
5. Field electromagnets
-Each electromagnet consists of a coil of many turns of copper wire wound on a soft iron core. The electromagnets are wound, mounted and shaped in such a way that opposite poles face each other and wrap around the rotor.
6. Brushes
-The brushes are carbon blocks that maintain contact with the ends of the coils via the slip rings (AC) or the split-ring commutator (DC), and conduct electric current from the coils to the external circuit.
Note:
In a compound wound generator, the shunt field is stronger than the series field. When the series field assists the shunt field, generator is said to be commutatively compound wound. On the other hand if series field opposes the shunt field, the generator is said to be differentially compound wound.
3. Compound Generator:
- Differential Compound generators are used to supply dc welding machines.
- Level compound generators are used to supply power for offices ,hostels and Lodges etc.
- Over compound generators are used to compensate the voltage drop in Feeders.

4. Separately Exited Generator:
- As a supply source to DC Motors, whose speed is to be controlled for certain applications.
- Where a wide range of voltage is required for the testing purposes.
The commutator rotates with the loop of wire just as the slip rings do with the rotor of an AC generator. Each half of the commutator ring is called a commutator segment and is insulated from the other half. Each end of the rotating loop of wire is connected to a commutator segment. Two carbon brushes connected to the outside circuit rest against the rotating commutator. One brush conducts the current out of the generator, and the other brush feeds it in.
The commutator is designed so that, no matter how the current in the loop alternates, the commutator segment containing the outward-going current is always against the "out" brush at the proper time.
The armature in a large DC generator has many coils of wire and commutator segments. Because of the commutator, engineers have found it necessary to have the armature serve as the rotor(the rotating part of an apparatus) and the field structure as the stator (a stationary portion enclosing rotating parts). Which is the inverse of an AC Generator.
Licup, Lexus
Mañalac, Kevin Ross
Pineda, Jheric
Ruiz, Eduardo C. Jr.
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