Electrical Troubleshooting

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.