EMM 214: Electrical Engineering I First Semester Examination

Electrical machines paper for mechanical engineers. Covers the working principle of a d.c. generator and the difference between separately excited and self-excited machines, the full power balance of a three-phase induction motor from air-gap power through converted and output power to efficiency, and the no-load parameters of a three-phase oil transformer. Asks for the three tests performed on transformers, the voltage equation of a d.c. machine, synchronous speed and rotor frequency of an induction motor, and how generated e.m.f. responds to changes in speed and pole flux. Closes on the three methods of controlling d.c. motor speed, the three-phase transformer connections and the line voltage, line current and output of a step-down transformer in each.