The 1959 Handbook of Power Resistors (3rd Edition), compiled by H.F. Littlejohn Jr. and published by the Ward Leonard Electric Company, is a comprehensive technical manual focused on the design, construction, and application of power resistors. Drawing upon over 50 years of practical experience, the handbook aims to provide engineers, technicians, and students with an in-depth understanding of power resistor technologies and their performance characteristics.

📘 Overview

This 195-page manual is structured into eight detailed sections:

1. General Resistor Considerations – Covers foundational principles such as Ohm’s Law, Kirchhoff’s Laws, and the fundamental functions of power resistors.

2. Materials for Resistors – Discusses construction materials, including resistive conductors, insulation, terminals, and protective coatings, along with their thermal and mechanical properties.

3. Types of Resistors – Provides detailed information on various resistor types developed by Ward Leonard, such as Vitrohm, Strip-ohm, Discohm, Ribflex, Edgeohm, Barohm, and Loopohm resistors, including their construction, mounting methods, ratings, and application data.

4. Criteria for Selection – Offers guidelines for selecting appropriate resistors based on factors like thermal capacity, voltage limitations, derating curves for different environments, and considerations for abnormal operating conditions.

5. Standard Types and Sizes of Resistors – Details standard resistor types and sizes, including specifications for various models like Axiohm, Vitrohm Tubular, and Strip-ohm resistors.

6. The Making of a Vitrohm Resistor – Explains the manufacturing process of Vitrohm resistors, providing insights into production techniques and quality control measures.

7. Resistor Standards – Outlines industry standards, including those set by the National Electrical Manufacturers Association (NEMA), to ensure consistency and reliability in resistor performance.

8. Definitions and Useful Data – Includes a glossary of terms, conversion factors, and reference tables for electrical, mechanical, and thermal equivalents, as well as symbols used in power, control, and measurement.

The handbook serves as both a technical reference and a practical guide, reflecting the extensive experience of Ward Leonard Electric Co. in resistor design and manufacturing. It is particularly valuable for those involved in the selection and application of power resistors in various electrical and electronic systems.