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Browse complete papersA solenoid of 80cm length carries 0.8A current. Calculate the number of turns required for a magnetic field strength \( H = 600AT/m \) at the center (ideal long solenoid approximation).
400
600
800
1000
Correct answer
400
Which of the following is NOT a standard excitation system for synchronous machines?
Rotating rectifier (AC) excitation system
Static excitation system
Brushless excitation system
Heat excitation system
Correct answer
Rotating rectifier (AC) excitation system
Determine the maximum output at given excitation, if a 3 - phase, 11 - kv, 6MVA Y-connected alternator has synchronous impedance of \( (1 + j10) \) ohm per phase. Its excitation is such that the generated line EMF is 14kV. If the alternator is connected to infinite bus-bars.
16.01MW
15.405MW
14.21MW
16.656MW
Correct answer
16.01MW
If a 105 - MVA, 10 - kV, 0.8 - PF - lagging, 50 - Hz and two-pole Y-connected synchronous generator has a per-unit synchronous reactance of 1.2 and a per-unit armature resistance of 0.02. then what is the torque angle \( \delta \) at these conditions?
28.6°
25.4°
45.1°
18.9°
Correct answer
28.6°
A power station has a load factor of 0.7 and a maximum demand of 14, 000kW . What is its average load?
9800kW
20000kW
2000kW
98000kW
Correct answer
9800kW
Maintenance and repair costs of a power plant are classified as:
Fixed cost
Interest on capital
Running cost
Amortization of the capital
Correct answer
Fixed cost
In a hydroelectric power plant, which component typically has the highest capital cost?
Civil structures (dams, tunnels, etc.)
Land acquisition
Transmission lines
Electromechanical equipment (turbines, generators, etc.)
Correct answer
Civil structures (dams, tunnels, etc.)
A 300km long, three-phase transmission line operates at 400kV and 50Hz. The inductance of the line is 0.97mH per kilometer per phase, and the capacitance is 0.0115µF per kilometer per phase. Assuming the line is lossless, calculate the characteristic impedance \( Z_{c} \).
290.43Ω
200.43Ω
177.36Ω
150.15Ω
Correct answer
290.43Ω
When reverse bias is applied to a p-n junction diode, it:
lowers the potential barrier.
rasies the potential barrier.
greatly decreases the minority carrier current.
greatly increases the minority carrier current.
Correct answer
lowers the potential barrier.
When a positive DC voltage is applied to the n-side relative to the p-side of a PN junction diode, the diode is under:
Forward bias
Reverse bias
Zero bias
Neutral bias
Correct answer
Forward bias