Q1. A. Sketch a main engine shaft driven generator arrangement with an electronic system for frequency correction. B. Describe the operation of the generator arrangement sketched in (A).
Q5. With reference to electronic control systems A. Draw a simple block diagram for temperature control B. Describe each component shown in the diagram in (a).
Q2. Sketch a circuit diagram for an automatic voltage regulator illustrating how the A.V.R. utilizes a Silicon-controlled rectifier to control the excitation system for an alternator.
Describe how the A.V.R. monitors output and controls the excitation system.
Q4. It is proposed to operate a bow thruster’s unit from a 3.3 KV electrical supply outline suitable option for the design of installation under each of the following heading. Protection of main switch board Overload of a bow thrusters motor Cable protection.
Q1. With reference to a three-phase shipboard electrical distribution system: (16)
a) Enumerate the advantages of an insulated neutral system.
b) Enumerate the disadvantages of an insulated neutral system.
c) Describe how the earthed neutral system is Earthed.
d) Compare the use of an insulated neutral system as opposed to the use of an Earthed neutral System with regard to the risk of electric shock from either system.
Q6. A. A series circuit having resistance, Inductance and capacitance is to be operated on a constant voltage supply of available frequency. Indicate graphically how changes will take place in the terms, Reactive terms, i.e. Capacitive reactance and inductance reactance; B. A resistance of 130 ? and a capacitor of 30µF are connected in parallel across a 230 Volt, 50Hz supply. Find the current in each component, total current, phase angle and the power consumed.
Q9. A. Explain the working principal of a 3-phase induction motor. What are the various types of rotors? B. An 18.65Kw, 6-pole, 50Hz, 3 phase slip ring induction motor runs at 960 rpm on full load with a rotor current per phase of 35A, allowing 1Kw for mechanical losses, find the resistance per phase of 3-phase rotor winding.
Q8. a) Explain why the iron losses in a transformer are substantially independent of the load current. (6)
b) The equivalent circuit for a 200/400-V step-up transformer has the following parameters referred to the low-voltage side. (10)
Equivalent resistance = 0.15 W; Equivalent reactance = 0.37 W
Core-loss component resistance = 600 W; Magnetising reactance = 300 W
When the transformer is supplying a load at 10 A at a power factor if 0.8 lag, Calculate,
i) the primary current
ii) secondary terminal voltage.
Q9. Sketch a graph of starting current, and torque against the speed of rotation for a single cage motor. B. A 230V motor, which normally develops 10Kw at 1000 rev/min with an efficiency of 85%, is to be used as a generator. The armature resistance is 0.15Ohm and the shunt field resistance is 220Ohm. If it is driven at 1080 rev/min and the field current is adjusted to 1.1A by means of the shunt regulator what output in Kw could be expected as a generator, if the armature copper loss was kept down to that when running as a motor.
Q10. A. Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse.
B. A coil having a resistance of 10 Ohm, and an inductance of 0.15 H is connected in series with a capacitor across a 100V, 50Hz supply. If the current and the voltage are in phase what will be the value of the current in the circuit and the voltage drop across the coil?
Username or email address *Required
Password *Required
Note: Entering wrong username in the login form will ban your IP address immediately. Entering wrong password multiple times will also ban your IP address temporarily.
Log in
Lost your password? Remember me
No account yet?
