Electrical Troubleshooting

Table of Contents

Chapter 1: Troubleshooting with Electrical Schematics

Topics: Symbols; Elementary diagrams; Power control and motor-starting circuits; Identifying conductors; Control panel layout; Sequence of operation

Learning Objectives:

• Identify a control relay on an electrical schematic.
• State the NEC requirements for fuses in ungrounded conductors.
• Explain component numbering on electrical schematics.
• Explain how conductors in a motor-control circuit are identified.

Chapter 2: Troubleshooting with Building Drawings

Topics: Architectural drawings; Installation diagrams; Electrical symbols on blueprints; Substation and power-installation drawings; Circuit tracing

Learning Objectives:

• Name the kinds of drawings used by electrical specialists.
• Identify electrical symbols commonly used for building diagrams.
• Describe a one-line diagram.
• Discuss the different types of drawing characteristics.

Chapter 3: Troubleshooting Control Circuits

Topics: Control-circuit functions; Conditions of protection; Troubleshooting pushbutton, sequence/control, motor, and overload circuits

Learning Objectives:

• Explain how severe three-phase voltage unbalance affects a three-phase motor.
• List the advantages of inherent protection.
• Explain how undervoltage release works.
• Describe how to troubleshoot a motor circuit.

Chapter 4: Troubleshooting Combination Starters

Topics: Using relay-troubleshooting charts; Latching-relay and timing-relay checks; Replacing relay coils; Troubleshooting control circuits, starters, and relays

Learning Objectives:

• List the reasons why a magnet coil burns or short-circuits.
• List the steps in troubleshooting a defective motor.
• Explain how a mechanical latching relay works.
• Explain how an electronic timing relay operates.

Chapter 5: Troubleshooting Control Devices

Topics: Reversing controllers; Using a checking-sequence chart; Autotransformer starters; Multi-speed motor starter controls

Learning Objectives:

• Demonstrate how to reverse the rotation of a three-phase induction motor.
• Explain the function of limit switches in reversing-motor applications.
• Describe how to use a checking-sequence chart.
• Select the best starter for use where it is undesirable to put a heavy load on the power supply.
• Explain how to change the speed of a squirrel-cage motor.

Chapter 6: Troubleshooting Special Controls

Topics: Selenium rectifiers; Testing rectifier diodes and three-phase rectifiers; Control-system logic; Static control; Time delay element

Learning Objectives:

• Explain the effects of age on a selenium rectifier.
• Name the protective devices used in electrical systems and pneumatic systems.
• State the definition of a bistable device.
• List the functions of a static control device.

Chapter 7: Troubleshooting DC Motors

Topics: Commutator discoloration; Brush sparking; Open winding; Vibration; Bearings; DC motor controls; Drum controllers

Learning Objectives:

• List causes of electrical and mechanical vibration in a dc motor.
• Explain how oil saturation affects brushes in a dc motor.
• Explain how maximum bearing operating temperature is determined.
• List problems in the motor control that can cause sudden or unexpected changes in motor speed.
• Explain how to salvage a water-soaked motor.

Chapter 8: Troubleshooting AC Motors

Topics: Grounded stator windings; Short-circuited and reversed phases; Open circuits; Incorrect voltage connections

Learning Objectives:

• Identify various kinds of three-phase motor failures.
• Demonstrate how to conduct a balanced-current test on a three-phase, Y-connected winding.
• List the symptoms of a reversed phase in a three-phase winding.
• Explain how to identify external leads that have become defaced.
• Demonstrate how to test for an open circuit in a split-phase motor.

Chapter 9: Troubleshooting Lighting Systems

Topics: Troubleshooting fluorescent, incandescent, mercury-vapor, and HID lamps; Low-voltage switching; Remote control; NEC requirements

Learning Objectives:

• Explain group replacement of lamps.
• Explain the function of a ballast.
• Describe an indication of normal fluorescent lamp failure.
• State the circumstances under which the number of relays used in a switching circuit may be a limiting factor.
• Explain how disconnecting hangers work.

Chapter 10: Saving Time in Troubleshooting

Topics: Tracing circuit problems; Equipment changes and modifications; Motor-location file

Learning Objectives:

• Name and describe the elements of a sequence of operation.
• List the features that must appear on an elementary wiring diagram to make it comply with JIC standards.
• List the steps in troubleshooting a new machine.
• List the information to be included in a motor location file.
• Select the best method for identifying a motor.

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