Đang tải... (xem toàn văn)
Electrician's troubleshooting and testing pocket guide
[...]... Electrician’s Troubleshooting and Testing Pocket Guide This page intentionally left blank Professional Want to learn more? We hope you enjoy this McGraw-Hill eBook! If you’d like more information about this book, its author, or related books and websites, please click here CHAPTER 1 Analog Test Instruments T raditional meters used by electricians and technicians for field testing and troubleshooting. .. terminal in turn and making the measurements Next, open the breaker and measure the insulation resistance between terminals by putting one lead on one terminal and the other on the second for a twoterminal breaker; for a three-pole breaker, check among poles 1-2, 2-3, and 1-3 Testing Safety Switches and Switchgear Completely disconnect from line and relay wiring before testing When testing manually... speed 20 Footcandle Meter A footcandle meter consists of a photosensitive element and a meter that indicates the average illumination of a room or other space in footcandles Typical footcandle meters can read light intensity from 1 to 500 footcandles or more To use the footcandle meter, first remove the cover Hold the meter in a position so the cell is facing toward the light source and at the level... from ground to terminals and between terminals When testing electrically operated switches check the insulation resistance of the coil or coils and contacts For coils, connect one megger lead to one of the coil leads and the other to ground Next, test between the coil lead and core iron or solenoid element Testing Ground Resistance Figure 1-13 shows the simplest method for testing the resistance of... for most testing, 1 Copyright © 2007, 2000, 1996 by The McGraw-Hill Companies, Inc Click here for terms of use troubleshooting, and maintenance purposes However, there are still many older analog meters in use, and a working knowledge of these diagnostic tools is useful to electricians and technicians This chapter briefly describes the various types of analog electrical meters and instruments, and how... connecting to and testing various types of equipment The following sections provide general guidance for common types of troubleshooting tests Testing Power Cables Figure 1-10 shows how to test cable insulation using a megger After both ends of the cable have been 13 1-10 Testing power cable disconnected, test the conductors one at a time, by connecting one of the leads to the conductor under test and connecting... terminals P1 and C1 of the megohmmeter to the ground under test, and terminals P2 and C2 to an all-metal underground water-piping system If the water piping covers a large area, its resistance should be very low (only be 17 18 1-13 Direct method of earth-resistance testing a fraction of an ohm) Thus, the megohmmeter reading will be that of the earth or grounding electrode being tested Miscellaneous Testing. .. leads to the conductor under test and connecting the remaining conductors (within the cable) to ground and then to the other (ground) test lead Testing DC Motors and Generators Disconnect a DC motor and a DC generator from its load Then attach the negative test lead of the megohmmeter to the machine ground and the positive lead to the brush rigging Measuring the insulation resistance in this manner indicates... current readings To minimize this problem, try to avoid using 3 clamp-on ammeters close to transformers, motors, relays, and contactors Ammeter Applications Ammeters are useful for troubleshooting various electrical components by indicating a change in electrical value Many examples and troubleshooting charts found throughout this book But here are two simple examples of ammeter applications Three-phase... indicator—similar to the “ting” of an air gauge and gives only approximate voltage readings 1-8 Testing fuses with a voltmeter 12 1-9 Common types of voltmeters Megohmmeters The megohmmeter (commonly called a megger in the field) is used to measure the resistance of insulation in megohms (thousands of ohms) Test results indicate the presence of dirt, moisture, and insulation deterioration Megohmmeter instruction . Electrician’s Troubleshooting and Testing Pocket Guide includes updated information vii Copyright © 2007, 2000, 1996 by The McGraw-Hill Companies, Inc. Click here for terms of use. on testing and troubleshooting. Exam Preparation Guide, and Handbook of Electrical Design Details. Copyright © 2007, 2000, 1996 by The McGraw-Hill Companies, Inc. Click here for terms of use. Electrician’s Troubleshooting and Testing Pocket. class="bi x0 y0 w0 h0" alt="" Electrician’s Troubleshooting and Testing Pocket Guide ABOUT THE AUTHORS H. Brooke Stauffer is Executive Director of Standards and Safety for the National Electrical