11:04 PM P T "168 76 EEE 316-Electr...chines | PQ..pdf K/S Phoenix Files 4th September, 2023. INSTRUCTIONS: Answer FIVE (5) QUESTIONS, DURATION: 3 HOURS QUESTION ONE: 1a) What is electromechanical energy conversion. (3 Mark: 1b) Explain the following terms: permanent magnets and non-permanent magnets (5 Mark: 1c) A short shunt generator delivers 45A at 240V and the resistance of the shunt field and armature: 500 and 0.030 respectively. Calculated the generated emf. (6 Marks QUESTION TWO: 2a) 2b) Energy can never be created or destroyed", discuss with examples Why is the air-gap very important in electromechanical systems. (4 Marks (4 Marks, 2c) A short shunt generator delivers 450A at 240V and the resistance of the shunt field and armature are 500 and 0.030 respectively. Calculated the generated emf. (6Marks) QUESTION THREE: 3a) 3b) List and explain the two types of armature windings mostly used in DC machines. Differentiate between electromechanical devices and machines with examples. (4 Marks) (5 Marks) 3c) An 8-pole DC generator has 500 armature conductors and a useful flux of 0.05Wb per pole. What will be the EMF generated if it is lap-connected and runs at 1200 rpm? What mut be the speed ar which it is to be driven produce the same EMF if it is wave-wound? (5 marks) QUESTION FOUR: 4a) Derive the equation of induced emf in a generator. (4 Marks) 4b) Compare and contrast electric circuits and magnetic circuits. (5 Marks) 4c) A 25kW, 250V, DC shunt generator has armature and field resistances of 0.060 and 1000 respectively. Determine the total armature power developed when working i) As a generator delivering 25kW output and. (5 Marks) ii) As a motor taking 25kW input. QUESTION FIVE: 5a) 5b) 5c) Enumerate the types of generators and discuss them briefly. List and six essential parts of a practical generator. (4 marks) (3 marks) A long-shunt compound generator rated 300 kW, 600 V has a shunt resistance of 75 02, armature resistance 0.03 n, winding resistance 0.011 02, series resistance 0.012 0, divertor resistance 0.036 Q. Calculate the voltage and power generated by the armature when the machine delivers power at full load. (7 marks) QUESTION SIX: 6a) 6b) State the principle of a motor operation and compare a generator with motor action. Discuss the significance of back EMF in DC motors. (3 Marks) (4 Marks) 6c) A direct current motor rated 240A, 480V has armature circuit resistance is 0.20. The machine has G poles and the armature is lap connected with 864 conductors. The flux per pole is 0.05Wb. Calculate The speed and. the gross torque developed by the armature. (7 Marks) QUESTION SEVEN: 0 Rotate ||| = Q Search n Share