Essay On Induction Generator

2.6.3. Induction Generator purpose:
Induction generator is commonly used in the wind turbine [7] electric generation due to its reduced unit cost, ruggedness, brushless rotor construction, and easy maintenance. Moreover, induction generators have several characteristics when compared to synchronous generator. The speed of the asynchronous generator will fluctuate according to the turning force (moment, or torque) applied on it. In actual the differences between the rotational speed at peak power and at idle is very small and it is approximately 1%. This is usually referred as the generator’s slip which is the difference between the synchronous speed of the induction generator and the actual speed of the rotor. This speed difference is a very essential variable for the induction machine. The term slip is used because it describes what an viewer riding with the stator field sees looking at the rotor which appears to be slipping backward. A more constructive form of the slip quantity results when it is articulated on a per unit basis using synchronous speed as the reference. The expression of the slip in per unit is shown below. A four-pole, 50 Hz generator will run idle at 1500 rpm according to the following formula. If the generator is producing its maximum power, it will be driven at 1515 rpm. A

The chord line is now defined as the straight line joining the ends of the camber line and is measured from this chord line. Cambered aerofoil is preferred to symmetrical aerofoil because they have higher lift/drag ratio for positive angles of attack. It is observed that the lift at zero angle of attack is no longer zero and that the zero lift occurs at a small negative angle of attack of approximately o. The center of pressure, which is at the ¼ chord position on symmetrical aerofoil has at the ¼ chord position on cambered aerofoil and moves towards the trailing edge with increasing angle of