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Q3. Differentiate between squirrel cage and wound rotor motor of the three phases: a.c. induction. In respect of the following; A. Rotor construction, B. Torque characteristic, C. Speed variation.

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.

Q4. What factors cause deterioration of the frequency response of a transistor amplifier? Explain their effect on the performance of the amplifier.

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

Q4. Differentiate with the aid of simple sketches between two of the following types of electronic circuits.

A. Rectifier circuit (6)

B. Amplifier circuit (5)

C. Oscillator circuit (5)

Q10. A. Why is a synchronous motor not self-starting? What are the various ways in which it can be started?

B. A 500V, single phase synchronous motor gives a net output mechanical power of 7.46kW and operates at 0.9 power factor lagging. Its effective resistance is 0.8 . If the iron and friction losses are 500 w and excitation losses are 800w, calculate the armature current and the commercial efficiency.

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.

Q10.  (a). Describe the no-load saturation characteristic of a d.c. generator.

(b). A 4-pole machine running at 1500 r.p.m. has an armature with 80 slots and 6 conductors per pole. The flux per pole is 6 x 106 lines. Determine the terminal e.m.f. of d.c. generator if the coils are lap connected. If the current per conductor is 100 A, determine the electrical power.

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. A. How does change to frequency affect the operation of the transformer? What makes this ratio different from the ratio of transformer? B. A 550 KVA, 50 Hz single phase transformer has 1875 and 75 turns in the primary and secondary windings respectively. If the secondary voltage is 220 V, calculate (i)Primary voltage; (ii)Primary and secondary currents; iii. Maximum value of flux.