Download Bridge Rectifier - Industrial Electronics - Past Exam Paper and more Exams Industrial Engineering in PDF only on Docsity! 1 Cork Institute of Technology Higher Certificate in Engineering in Electrical Engineering – Stage1 (National Certificate in Electrical Engineering - Stage 1) (NFQ – Level 6) Autumn 2005 INDUSTRIAL ELECTRONICS (Time: 3 Hours) INSTRUCTIONS: Answer Five Questions. All formula and calculations must be shown. Examiners: Mr. K. O’Connell Mr. M. Ahern Mr. R. Daly Q1 (a) Using the reference points in Fig. 1, explain the operation of the full-wave bridge rectifier circuit (without the capacitor) and indicate the polarity at the output terminals C and D. 6 marks ~ ~ D1 D4 D2 D3 230 V 50 Hz. 18 V C + A B C D Fig.1 (b) Calculate for the circuit: (i) the maximum voltage at AB; (ii) the peak voltage at the terminals CD. 4 marks (c) Show for the circuit fully detailed waveforms for: (i) the voltage at the terminals AB; (ii) the voltage at the terminals. 10 marks 2 Q2 (a) Construct a 5-column binary table with appropriate headings to represent the decimal numbers from 0 to 15. One of the columns must show the decimal. 5 Marks (b) Show how the expression: Q = (A • B • C) + (A • B • C) + (A • B •C) is implemented using logic gates 6 Marks (c) Show using logic gate circuit diagrams, how bit data A and B can be compared for: (i) A less than B, (ii) A equal to B, and (iii) A greater than B. 9 Marks Q3 (a) Draw a clearly labelled circuit diagram for an LED connected to a 24V d.c. supply and calculate the resistance required to limit the current in the LED to 50mA. Assume the LED operating voltage to be 3.0V. 4 marks (b) Redraw the circuit with modifications for connection to an a.c. supply of the same voltage. 3 marks (c) Show the graphical representation of a seven-segment display and the standard markings for each segment. 4 marks (d) Show by means of LED representation a common anode seven-segment display connected to a BCD to 7-segment decoder. 9 marks Q4 (a) Fig. 2 shows a circuit designed to operate the coil of a 12V relay when light to the LDR is exposed. Given a coil resistance of 300Ω, calculate the rated coil current and the minimum base current required for a collector current of this value. 6 marks (b) The resistance of the LDR varies from 2kΩ to 500kΩ from being exposed to light and covered, respectively. Calculate the approximate base current when the LDR is exposed to light. 5 marks (c) Calculate the voltage at the junction of R1 and R2, when R1 is covered and the base is disconnected from the junction. Explain using your calculated answer if the relay will de-energise with this condition when the junction is reconnected to the base. (Assume R2 = 5kΩ) 6 marks (d) Explain why the diode is connected across the relay coil. 3 marks
