Cork Institute of Technology
Higher Certificate in Engineering in Electrical Engineering – Award
(NFQ Level 6)
Autumn 2006 Electrical Power Systems & Equipment (Time: 3 Hours)
Instructions Answer FIVE questions. All questions carry equal marks Examiners: Mr. J. C. Duggan Mr. M. Hennessy Prof. E. McQuade
The start-up sequence for an industrial plant is specified below. Control is by single stop and start push buttons. Motors M1, M2 and M3 are to be started in sequence with 10s intervals between each start. After M3 has started a solenoid value, SV1, is to operate for 1 minute and then turn off. An O/L on any motor stops all. An emergency stop is required. Develop a suitable control circuit. (20 marks)
A 400V. 50Hz industrial supply has an impedance of 0.0013 + j 0.0061Ω. Cables from transformer to L.T bus-bars have a resistance of 0.15mΩ. A balanced three phase shortcircuit occurs on the bus-bars. Using the information supplied in appendix A and diagrams 3 or 4 de..