DieselShip's Online Content Library

Q7. With reference to Dynamic positioning systems what do you understand by the term “redundancy”? With the aid of simple block diagrams explain the difference between DP-I, DP-II and DP- III system enumerating their relative advantages and dis advantages.

Q2. Tank liquid level sensors are an integral part of ships. Describe with aid of suitable sketches the working principle of,

(a) capacitive type level sensor;

(b) Ultrasonic level sensor;

(c) Float.

Q2. A. With respect to measuring instruments what is the difference between analogue and digital measuring instruments. Explain the working principle of each type.

B. Describe with the aid of simple sketches one analogue and one digital measuring instrument you have used onboard.

Q1. What are semiconductor devices? What are its advantages over thermionic devices? With respect to semi-conductor devices describe working principle and application of the following;-

 A. Zener Diode,

B. Transistor,

C. Photocell,

D. Thyristor

Q4. With reference to the use of electrical equipment in hazardous areas on ships, describe the following in detail: - A. Ex-d; B. Ex-I; C. Ex-p:, D. Ex-o:, E. Ex-q:, F. Ex-n

Q7. A 3-phase slip ring induction motor gives a reading of 60V across the slip rings on open circuit, when at rest with normal stator voltage supplied. the motor is star connected and has an impedance of 0.6 + j6 ohms/phase. find the rotor current and its power factor when the machine is 1. At standstill with slip-rings joined to a star connected starter with a phase impedance of 5+j4 ohm 2. Running normally with a 4% slip.

Q7. A circuit consists of two coils connected in series. Each coil has a resistance of 17.32 ohms with a reactance of 4 ohms. The circuit is connected to a 240v 50Hz ac supply. Calculate A. The total current in the circuit and its phase angle B. The voltage across each coil and their phase angle.

Q8. A current has the following steady values in amperes for equal intervals of time and changing instantaneously from one value to next: - 0,10,20,30,20,10,0,0, -10,-20,-30,-20,-10,0 etc. Calculate I. Average value 2. RMS value, 3. Form factor and peak factor.

Q9. A 250V DC shunt motor takes a line current of 6 Amps @ no load. the armature and field resistances are 0.1 Ohm and 125 Ohm respectively. Determine A. Rotation power loss B. Efficiency of motors when full load current is 150 Amps C. The percentage change of speed from no load to full load assuming the rotational losses to be constant.

Q10. the following loads are supplied by two alternators running in parallel 1. 1400kw@pf 0.86 lagging 2. 900 kw @ pf 0.8 lagging. 3. 800 kw @ pf unity 4 500kw @pf0.8 leading. If the load on one machine is adjusted to 2100kw @ pf of 0.92 find the load and p.f of the other machine.