Tuesday, November 12, 2013

Synchronous and Asynchronous Generators


CONTENTS :
1. SYNCHRONOUS GENERATOR ( multipole ) .
2 . ASYNCHRONOUS GENERATOR .
INTRODUCTION .
The generator converts the mechanical energy produced by the rotor into electrical energy. Asynchronous generators are often used squirrel cage with capacitor banks to improve power factor, but also can be used for asynchronous and synchronous generators winding rotor . The network connection may be direct or indirect , depending on whether the turbine operates at constant or variable speed . Working indirectly connected network leverage peaks get wind speed, but the generator produces power at variable frequency needed fitness equipment to dump energy in the network. In the direct connection , the network itself limited the rotational speed of the generator , so that no peaks greater advantage wind energy.
1. SYNCHRONOUS GENERATOR ( multipole ) .
The synchronous motor is unconventional and can be used in large industries for power factor correction in this case , the speeds of the rotor and stator tend to equalize , thus the name Synchronous .

Figure 1: Synchronous Generator .
Advantages and disadvantages :
- Optimized control .
- Does not use multiplier .
- Low slip .
- Reduction of stress.
Two . ASYNCHRONOUS GENERATOR .
An induction motor is a conventional engine and the term asynchronous is used , because the rotor speed theoretically can never reach the speed of the stator ( Offset) .

Figure 2: Asynchronous Generator .
The squirrel cage motor comprising a rotor constituted by a plurality of metallic conductors (typically aluminum ) arranged parallel to each other , and short-circuited at its ends by metal rings , that is what forms the squirrel cage call for its visual similarity with a squirrel cage . This ' cage ' is filled with material, usually stacked plate . Thus, a system is achieved n -phase conductors (n being the number of drivers ) located inside the rotating magnetic field created by the stator , which has a physical system is extremely effective , simple, and very robust ( basically no maintenance required ) .
The wound rotor motor having a rotor constituted , instead of by a cage, of a series of conductors wound about it in a series of slots on its surface. In this way, a winding inside the stator magnetic field , the same number of poles ( must be built with great care ) , and moving. This rotor is much more complicated to manufacture and maintain than the squirrel cage , but allows access to it from the outside through rings that are the windings shorted . This has advantages such as the possibility of using a motor starter that can adjust the speed and torque , as well as reduce the starting current .
In either case , the rotating magnetic field produced by the stator field coils generate induced currents in the rotor , which are used to produce this movement .
1) Asynchronous ( squirrel cage ) .

Figure 3: Asynchronous Generator squirrel cage .
Advantages and disadvantages :
- Easier to manufacture.
- Less versatility.
- Need soft synchronization network ( thyristors ) .
- It controls the power factor capacitor stages needed .
2 ) Asynchronous with wound rotor .

Figure 4: Asynchronous Generator rotor winding.
Advantages and disadvantages :
- Allows inject and extract energy from the rotor.
- Injecting different frequencies to generate power rotor is achieved at very different speeds of synchronism .
- Variable speed generator ( of 900-1500 rpm).
- By allowing the extraction of energy from the rotor, is able to generate up to 10% of the energy produced .
- Requires synchronization before generating network .
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