Understanding Motor Controls 3rd Edition

Book Preface

Note from the Author

I have taught the subject of motor control for over 30 years. I have tried different methods and found that some are more successful than others. Understanding Motor Controls is the accumulation of this knowledge. I am sure other methods may work equally well, but the methods and information presented in this textbook have worked the best for me.

My goal in writing this textbook is to present the subject of motor control in a way that the average student can understand. I have three main objectives:

• Teach the student how to interpret the logic of a schematic diagram.
• Teach the student how to properly connect a circuit using a schematic diagram.
• Teach the student how to troubleshoot a control circuit.

Understanding Motor Controls assumes that the student has no knowledge of motor controls. The student is expected to have knowledge of basic Ohm’s law and basic circuits, such as series, parallel, and combination. The book begins with an overview of safety. A discussion of schematics (ladder diagrams) and wiring diagrams is presented early. The discussion of schematics and wiring diagrams is intended to help students understand the written language of motor controls. Standard NEMA symbols are discussed and employed throughout the book when possible. The operation of common control devices is presented to help students understand how these components function and how they are used in motor control circuits. Basic control circuits are presented in a manner that allows students to begin with simple circuit concepts and progress to more complicated circuits.

The textbook contains examples of how a schematic or ladder diagram is converted into a wiring diagram. A basic numbering system is explained and employed to aid students in making this conversion. This is the most effective method I have found of teaching a student how to make the transition from a circuit drawn on paper to properly connecting components in the field.

Understanding Motor Controls also covers solid-state controls for both DC and AC motors. Variable frequency drives and programmable logic controllers are covered in detail. I explain how to convert a ladder diagram into a program that can be loaded into a PLC. The book contains many troubleshooting problems that help the student understand the logic of a control system. Circuit design is also used to help the student develop the concepts of circuit logic.

Understanding Motor Controls contains 16 hands-on laboratory exercises that are designed to use off-the-shelf motor control components. A list of materials and suggested vendors is given for the components used in the exercises. The laboratory exercises begin with very basic concepts and connections and progress through more complicated circuits.