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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2012
Module Title: Advanced Plant Automation
Module Code: ELEC
School: School of Mechanical, Electrical and Process Engineering
Programme Title: Bachelor of Science Honours in Electrical Power Systems - Award
Programme Code: EELPS_8_Y
External Examiner(s): Mr Colm Murray, Ms Mary Desmond Internal Examiner(s): Mr Gerard Geaney
Instructions: Answer all Four questions. Complete diagrams where appropriate.
Student signature: ___________________________________________________
Duration: 2 Hours
Sitting: Autumn 2012
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
Q1:
a) Explain the term “muting” when designing electrical circuitry to comply with safety requirements in accordance with EU directives on dangerous machinery. (5 marks)
b) Design a motor DOL starter circuit connected to the relay unit to comply with category 2 safety requirements. Draw the control and power circuit involved. Explain fully, the operation of the circuit. Contact numbering to be used throughout for reference purposes. (15 marks)
c) Explain clearly, by means of the diagram references to the motor DOL starter circuit (category 2) what is meant by the term Autochecking (circuit monitoring)? (5 marks)
Q2:
a) Describe by means of a diagram, the IEEE-754 binary representation for a 32-bit floating- point value and explain how the value is interpreted. ( 6marks)
b) Convert the decimal value 98765.875 to (2n x 1. f ) format and show its 32-bit binary digit representation. Show all the steps in arriving at the converted solution. (13 marks)
c) Show the valid range of negative and positive values in 2n x 1.f format that can be supported in 32 bit floating-point format in accordance with IEEE-754. Use your calculator to convert these to decimal values in 10n exponent format and write down the complete decimal range. (6 marks)
Q3:
a) Explain the difference between an absolute encoder and an increment encoder. (4 marks)
b) A method of increasing the resolution of a single track increment encoder, is to use two emitters and receivers (This quadruples the resolution). Explain how this is achieved. (13 marks)
c) Explain the difference between Maximum Permissible Speed and Maximum Response Frequency when selecting an encoder for a process. (4 marks)
d) Why is grey code commonly used with absolute encodes? (4 marks)
