# Power Systems Questions and Answers – Water Turbines

This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Water Turbines”.

1. Kaplan turbine is _____________
a) axial flow turbine
b) inward flow turbine
c) tangential flow turbine
d) mixed flow turbine

Explanation: In Kaplan turbine water strikes the turbine blades axially. That’s why Kaplan turbine is an axial flow turbine. Kaplan turbines are special type of turbines for low head applications.

2. Pelton turbines are used for __________________
c) in steam power plants

Explanation: Pelton turbines are impulse turbines and are suitable for high head low flow plants. Pelton turbines consist of elliptical shaped buckets along its Periphery. Water is released from nozzle to the buckets of turbine.

3. Francis turbines are the type of _____________
a) reaction turbines
c) impulse turbine
d) axial flow turbine

Explanation: Francis turbines are inward mixed flow type reaction turbines. Such turbines develop power partly due to velocity of water and partly due to difference in pressure acting on the front and back of the runner blades.

4. Operating head of Francis turbine is __________
a) less than 30
b) less than 70 m
c) 30 to 200 m
d) more than 200 m

Explanation: Francis turbines are medium head(30 to 200 m) and medium flow turbines. Using it for low or high head will cause inefficient operation. Their life is about decades so maintenance cost is low.

5. Which of the following is not a reaction turbine?
a) Francis turbine
b) Kaplan turbine
c) Pelton wheel turbine
d) Propeller turbine

Explanation: When the entire pressure of water is converted into kinetic energy in a nozzle and the jet thus formed drives the wheel then the turbine is called impulse turbine. Pelton turbine works in similar way, so it is an impulse turbine. Francis, Kaplan and propeller turbines are reaction turbines.
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6. Inside pressure of which of the following turbine is equal to atmospheric pressure?
a) Fixed vane propeller turbine
b) Movable vane propeller turbine
c) Francis turbine
d) Pelton wheel turbine

Explanation: Francis and propeller turbines are totally submerged in water, the turbine casing is full of water. As the water flows through the turbine blades, its pressure changes. Also the discharging water creates negative pressure below the turbine blades. Pelton turbines are fitted in open air and water Jet is forced into its blades by nozzel so it’s inside pressure is equal to atmospheric pressure.

7. Francis turbine is suitable for medium head hydroelectric power plant.
a) True
b) False

Explanation: Francis turbines are medium head and medium flow turbines. Kaplan turbines are low head high flow turbines. Pelton turbines are high head and low flow turbines.

8. Which turbine has highest speed?
a) Pelton wheel turbine
b) Francis turbine
c) Impulse turbine
d) Kaplan turbine

Explanation: Francis turbine has a specific speed of 60 to 300 rpm. Specific speed of Pelton turbine is lowest. Speed of Kaplan turbine is 2 to 3 times more than that of Francis turbine.

9. Governing mechanism used in case of Pelton wheel turbine is ________
a) guide vane
b) nozzle needle
c) control valve
d) dam gates

Explanation: During load variation it is necessary to maintain the speed of the alternator constant. This is achieved by controlling the flow of water entering the turbine by the help of automatic adjustment of guide vanes for reaction turbine and the nozzle needle is in case of impulse turbine. Such an operation of speed regulation called governing and the system used to do this is called governor.

10. Guide vanes are used as governor in Kaplan turbine.
a) True
b) False

Explanation: Guide vanes are used as governor in Francis and Kaplan turbines. These guide vanes controls the flow of water to the turbine and hence governs the speed of rotation of turbine. Under different loading conditions the speed of rotation of turbine is needed to be controlled for constant frequency output.

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