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CHAPTER SOLENOIDS, CONTACTORS 5.0 TABLE OF CONTENTS 5.1 INTRODUCTION 1 5.2 FAILURE MODES 3 5.3 FAILURE RATE OF SOLENOID ASSEMBLY 5 5.3.1 Temperature Multiplying Factor 6 5.3.2 Application Service Factor 7 5.4 FAILURE RATE OF CONTACTOR ASSEMBLY 8 5.5 REFERENCES 16 5.1 INTRODUCTION This chapter includes the procedures for estimating the reliability of solenoids and contactors in their intended operating environments. Solenoids are used to control the motion of other mechanical components such as valves and actuators. The most accurate method for predicting the failure rate of these assemblies is to sum the failure rates for the individual parts that make up the assembly. Procedures for estimating the failure rate of valves and actuators and the parts comprising these assemblies such as springs and bearings are contained in various chapters of the Handbook. In the event the solenoid is part of a relay, Section 5.4 of this chapter contains the procedures for estimating the failure rate of the contactor assembly. Solenoids are electromechanical devices that convert electrical energy into mechanical motion. Generally this motion is used to move a load a specified distance or rotational angle within a specified time. Linear magnetic solenoids usually produce motion by pulling a plunger into the coil when energized. They can also be equipped with a push rod mounted to one end of the plunger providing a pushing motion when energized. The plunger of the solenoid assembly, also known as the armature, is made of ferrous material to increase magnetism or permeability. Rotary solenoids convert axial motion into a rotary stroke. Component parts of a solenoid include a coil to carry current and generate ampere turns, an iron shell to provide a magnetic circuit and a movable plunger to act as the working element. Component parts of example linear and rotary solenoids are shown in Figure 5.1. Electrical current is supplied to the solenoid coil that is wound tightly Solenoids, Contactors 5_<| Revision E

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