Alternating Current Circuits SAMPLE. Learner Workbook. Version 1. Training and Education Support Industry Skills Unit Meadowbank. Product Code: 5632

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1 Learner Workbook Version 1 Training and Education Support Industry Skills Unit Meadowbank Product Code: 5632

2 First published in August 2012 by Training and Education Support, Industry Skills Unit, Meadowbank Level 3, Building J, See Street Meadowbank NSW 2114 This work is copyright. Any inquiries about the use of this material should be directed to the publisher. New South Wales Technical and Further Education Commission 2012 ISBN FEEDBACK We value your opinion and welcome suggestions on how we could improve this resource manual. Keep in mind that the manual is intended to help students learn and is not a text book. Send your comments and suggestions to: Program Manager Training and Education Support, Industry Skills Unit, Meadowbank Level 3, Building J, See Street Meadowbank NSW 2114 Ph: Fax:

3 Table of contents Introduction Alternating Current Quantities Vector/Phasor Diagrams Single Element a.c. Circuits RL Series a.c. Circuits RC Series a.c. Circuits Revision, Consolidation and Assessment RLC Series a.c. Circuits RL, RC and LC Parallel a.c. Circuits RLC Parallel a.c. Circuits Power in an a.c. Circuit Power Factor Improvement Revision, Consolidation and Assessment Three Phase Systems and Harmonics Three Phase Star Connections Three Phase Four Wire Systems Three Phase Delta Connections and Star-Delta Connections Energy and Power Requirements in Three Phase Systems Revision, Consolidation and Assessment Review Questions - Answers Sample Theory Assessment 1 - Answers Sample Theory Assessment 2 - Answers Sample Theory Assessment 3 - Answers TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

4 Risk Assessment Terminology Supervision Level: D Direct This means the personal supervision of a learner, at all times, on a direct and constant basis, within visual contact and/or earshot. Constant basis refers to the continuous supervision of tasks being performed for the first time and until skill is demonstrated for the complexity of the task and work environment. G General This means the learner does not require constant attendance of the supervisor but requires personal contact with an experienced worker on a recurrent basis when working. Periodic supervision means being under instruction and direction for tasks being formed with checks and test being made prior to the commissioning of apparatus/equipment. B Broad This means the learner does not require constant supervision but requires personal contact with an experienced worker on at least a regular/ occasional basis when working. Occasional supervision means being under instruction and directino with checks being carried out on completion of multi-tasks. Risk Classes: A high risk Potential death or permanent disablement. B medium risk Potential serious injury/illness and temporary disablement. C low risk Potential minor injury, no lost time. Page 6 of 417 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

5 1. Alternating Current Quantities Purpose In this section you will learn about the electrical quantities associated with an a.c. waveform and how to use the cathode ray oscillosscope (cro) to measure a.c. waveform parameters. You will also learn how to apply trigonometric methods to solve electrical problems associated with a.c. waveforms. Objectives At the end of this section you should be able to: state and apply the sine, cosine and tangent ratios of a right-angle triangle use a scientific calculator to find the sine, cosine and tangent of any angle define the term alternating current and list its main advantages compared to direct current list basic applications for and identify the wave shapes for d.c, square, triangular and sine wave voltages and currents sketch a sine wave and show on the waveform the rms, peak to peak and the peak voltages as well as the period of the waveform calculate from a drawing of an alternating waveform the maximum value, peak to peak value, period and the frequency calculate the instantaneous electrical values from a sinusoidal waveform given the maximum electrical values and angle/time through which the wave has passed define the terms crest factor and form factor for a sinusoidal a.c. wave form. correctly adjust the controls of a basic cathode ray oscilloscope (CRO) to obtain a trace on the screen use the calibrate function of a CRO to check the calibration of the instrument measure voltage levels of a d.c. and an a.c. signal using a CRO use a CRO to determine the phase difference between two sinewaves. Technical Information You will find the information to undertake this section in the following references. At least one reference text should used. References Jenneson, J.R., 2010, Electrical Principles for the Electrical Trades, 6 th Ed., McGraw-Hill, Sydney. Hampson, J., 2011, Electrical Trade Principles - A Practical Approach, 2 nd Ed., Pearson Education, Sydney. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 7 of 417

6 Phillips, P., 2012, Electrical Principles, 2 nd Ed., Cengage Learning, Melbourne. Batty, I., 1997, More Electrical Principles, Prentice Hall, Sydney, Chapters 6, 7 and 8. Lowe J.F., Electronics for the Electrical Trades, 4 th Ed., McGraw Hill, Sydney, Unit 1. Van den Bergen, B., 1995, Mathematics for the Electrical Trade, TAFE Publications, RMIT, Melbourne, Chapter 6. Page 8 of 417 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

7 Student Exercises Student Exercise 1.1 Complete the table below. Student Exercise 1.2 Angle θ Sin θ Cos θ Tan θ A sine wave has a maximum voltage of 340 volts. Determine the instantaneous value of voltage at angles of: (a) 45 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 9 of 417

8 (b) 120 (c) 270 Student Exercise 1.3 A sine wave has a maximum current of 20 A and a frequency of 50 Hz. Determine the instantaneous value of current after: (a) 6 ms (b) 9 ms (c) 15 ms. Page 10 of 417 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

9 Student Exercise 1.4 For the waveform of Figure 1.1, determine the: (a) peak-to-peak value (b) period (c) frequency Figure 1.1 Student Exercise 1.5 A sine wave has a maximum voltage of 340 V. Determine the rms value of voltage for the sinewave. Student Exercise 1.6 An appliance plate shows that the a.c. current drawn by the appliance is 10 A. Determine the maximum current value for the appliance. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 11 of 417

10 Student Exercise 1.7 For the CRO display of Figure 1.2 determine the following: (a) (b) (c) (d) peak-to-peak voltage peak voltage periodic time waveform frequency Channel A (or 1) vertical gain Channel B (or 2) vertical gain = 1 V/DIV = not considered Time base Answers = 0.1 ms/div Figure 1.2 (a) (b) (c) (d) Page 12 of 417 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

11 Practical Exercise 1.1: Using a Cathode Ray Oscilloscope Task To learn the basic procedures for setting up the cathode ray oscilloscope (CRO) controls. Equipment Your teacher will provide you with the specifications of the equipment to be used. Safety Function generator (an audio signal generator can also be used) Dual trace cathode ray oscilloscope (CRO) Specification All voltages are dangerous - stay alive by working dead. Follow correct isolation procedures. Isolate circuits before connecting and disconnecting. Circuit components may become hot when connected into a circuit. Follow material handling safety procedures at all times. Risk Assessment Identify any hazards, list the supervision level (D, G or B), list the risk class (A, B or C) and list control measures required in the table below: Hazard Identification Supervision Level Risk Class Control Measures TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 13 of 417