PELTON TURBINE OR PELTON WHEEL TURBINE
Pelton turbine or Pelton wheel turbine is basically an impulse turbine. This turbine is suitable for high head and low flow plants. Pelton wheel turbine is used when water head is more than 200 meters.According to the turbines get,generally, two types of Pelton turbine are used in hydroelectric power plant.When a single jet is used horizontal shaft type Pelton turbine is used and vertical shaft type Pelton turbine is suitable for 2 or 4 jets.Most of the Pelton turbines are horizontal shaft type.Horizontal shaft type water turbine have two nozzles but more than two nozzles,vertical shaft type water turbine is used.The diagram of Pelton wheel is shown below
In Pelton turbine,The potential energy of water in the penstock is converted into kinetic energy into water and it passes from a nozzle. In the turbine,inside pressure of water is same as the atmospheric pressure. It consists of the rotor which is placed in between an elliptical shaped buckets along with the periphery of the turbine. The rotor of the runner is made of cast steel, bronze or stainless steel. The buckets are bolted on to the runner and integral casting of buckets with the runner is also possible. High-pressure water coming from the penstock fall into the buckets and it causes the rotor starts to rotate. After doing useful work, water is discharged into the tail race. But how much quantity of water is discharged by tail race,is completely controlled by the nozzle and a needle tip is placed in the nozzle.This needle tip is controlled by the governor. When load the decreases on the turbine, the governor pushes the needle tip into the nozzle and as a result quantity of water striking reduces the buckets,thereby a small amount of water strike into the turbine.Again load increases on the turbine,needle tip is away from the nozzle and consequently more waterfall into the turbine.A Needle is also controlled by a speed deflector.The buckets are fixed with runner and it is placed nearer to the tail race.Since this turbine is suitable for high head,so long penstock is used.
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