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Correct option is (a) PURE tension

Easy explanation: Darrieus wind mill has two or three thin, curved blades with airfoil cross SECTION and constant chord length. Both ends of blades are attached to a VERTICAL shaft. Thus the force in the blade due to ROTATION is pure tension.

Correct choice is (c) 3

Explanation: TURBINES with three blades are used to avoid VIBRATIONS that occur due to the turning or YAWING of the rotor in order to face in into the wind. However, this problem can be OVERCOME by controlling the YAW rate.

Correct option is (a) 0.155KW

Explanation: TOTAL power P,

P = 0.245 X (πD^2/4)

= 0.245 X (π (90)^2/4)

= 0.155KW.

The correct option is (a) AVAILABILITY FACTOR

The best I can explain: The availability factor is defined as the fraction of time during a given period that the turbine is ACTUALLY on LINE. The actual wind velocity at the propeller hub that determines the turbine power is usually higher.

The correct answer is (a) To PROTECT WHEEL against DAMAGE

Easy explanation: To protect the TURBINE wheel against damage at very high wind VELOCITIES, it is designed to stop operation (such as feathering the blades) at cut out velocity. Thus the wind turbine operates at rated velocities and at constant power between the rated and cut out velocities and ceases the operation above the cut out velocity.

The correct ANSWER is (c) Wind mill head

For explanation: The wind mill head supports the rotor, housing, and rotor BEARINGS. It ALSO has control mechanism like CHANGING the pitch of the blades for safety devices, tail vane to orient the rotor to face the wind. Its body is the size of the mini BUS.

The CORRECT option is (a) Horizontal axis with two aerodynamic blades

The BEST I can explain: In horizontal axis with two aerodynamic type windmill the machine ROTOR drives through a step up gear box. The blade rotor is DESIGNED to orient downwind of the tower. The components are mounted on bed plate which is attached on a PINTLE at the top of the tower.

Right choice is (c) Pin wheels

Easiest explanation: A pinwheel is a windmill-style turbine that spins PERPENDICULARLY to the wind AFFECTING it. Like wind socks and WEATHER vanes, a pinwheel can be attached to a rotating BASE. This allows the pinwheel to change direction with the wind, and it will spin facing into the oncoming wind.

Right choice is (a) LARGE machines

To explain: Large wind turbines are those of 100 kW RATED CAPACITY or greater. They are used to generate power for distribution in central power GRIDS. They can have single generator at a single site or multiple generators sited at several places over an area.

Correct answer is (B) LONG length of blades

For explanation I WOULD say: Wind turbine experiences change in velocity DEPENDENT upon the blade inlet angle and the blade velocity. Since the blades are long, the blade velocity varies with the radius to a greater degree than steam or gas-turbine blades and the blades are THEREFORE twisted.

Correct OPTION is (c) Tower mill

Easiest explanation: Tower mills are further IMPROVEMENTS on smock mills. They have a rotating cap and permanent body, but this body is made of brick or STONE. This fact MAKES it possible for the towers to be rounded. A ROUND structure of it allows for large and taller towers.

Right option is (c) Horizontal axis MULTI bladed TYPE wind mill

The explanation is: Horizontal axis multi blade windmill is made from sheet metal or aluminum. The rotors have high strength to weight ratios. They have good power COEFFICIENT, high starting torque and added ADVANTAGES of simplicity and LOW cost.

Right option is (c) 1854

For explanation I would say: Invented by Daniel Halladay in 1854, the Halladay Standard was the FIRST commercially successful self-governing windmill in 1854 was the firms of Halladay, McCray & Co., ELLINGTON, CONN. Partners in the company were INVENTOR Daniel Halladay, John BURNHAM and Henry McCray.

Correct answer is (B) Large wind turbine

Easy explanation: The rate of rotation of large wind turbine GENERATORS operating at rated capacity or below is CONTROLLED by varying the PITCH of the rotor blades. It has low rpm, about 40 to 50. It is necessary to increase greatly the low rotor rate of turning using transmission mechanism.

Correct choice is (B) 220 feet

Explanation: Large utility-scale wind TURBINES can now generate more than a MW of electrical power each and deliver electricity DIRECTLY in to the electric grid, these turbines are placed at 200 feet HEIGHT at the rotor hub and have BLADES which are 220 feet or more in diameter.

Right option is (a) 20,000 MW

The explanation: India has a potential of 20,000 MW of WIND power. Wind power ACCOUNTS nearly 9.87% of India’s TOTAL installed power generation capacity. Generation of wind power in India mainly account from southern state of India.

Right choice is (b) Air foiled type cross SECTION

Easiest explanation: WIND turbine blades have an air foiled type of cross section and a variable pitch. They are slightly twisted from the outer tip to the root in order to reduce the tendency for the rotor to stall. The blades can ALSO have CONSTANT chord length.

Right answer is (a) Because they pose POWER oscillations problems

To explain: Severe fluctuations in power are always undesirable, because they pose power oscillation problems on the grid and severe strains on the windmill hardware. From an economic point of view, a windmill is designed to produce a rated power output corresponding to MAXIMUM, or near maximum, PREVAILING WIND velocity at a given site would generate low powers, with full capacity of the turbine and electric generator unused much oftime.

Right answer is (d) Because of their high EFFICIENCY

The best explanation: Fixed ratio GEARS are recommended for TOP mounted equipment because of their high efficiency, and minimum system risk. For bottom mounted equipment requiring a right angle drive transmission costs can be reduced on the HUB by increasing ROTOR speed to generator.

The correct ANSWER is (a) Turbine

Easy explanation: Wind turbine blades capture wind ENERGY, a form of mechanical energy, and PUT it to work turning a drive shaft, GEARBOX, and generator to produce electrical energy. Many factors affects wind turbine efficiency including turbine blade aerodynamics.