What’s a solenoid coil?

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A solenoid coil is a wire wound tightly around a conductive core with a hollow center, creating an electromagnet used for linear motion to switch or drive devices. They can be replaced if damaged, but some are sealed, like automotive starter solenoids.

A solenoid coil is a wire wound tightly around a conductive core with a hollow center. When an electric current is passed through the coil, a magnetic field is created, effectively forming an electromagnet. In most solenoid applications, this magnetic potential is used to do some kind of work. In most cases, the energy provided by electromagnetic energy is translated into a simple linear motion to switch or drive a variety of devices. Solenoid coils are generally modular units that can be removed and replaced if necessary, although sealed units are quite common as well.

Solenoids are among the simplest and most widely used forms of linear drive devices and are entirely dependent on the principles of electromagnetic energy for their operation. At the heart of any solenoid is the solenoid coil. This part of the solenoid consists of a tightly wound coil of wire that is normally wound on an insulated coil. The coil is placed on a conductive core typically made of a ferrous metal that forms the body of the electromagnet. In the most common configurations, the metal core is made with a hollow center designed to accommodate a spring-loaded armature or plunger.

When an electric current is passed through the solenoid coil, an electromagnetic field is induced in the core. This pushes the armature against the spring tension toward the center of the core, thus supplying the linear motion that activates whatever device the solenoid is connected to. When the electrical supply ceases, the field collapses and the spring pulls the armature out of the core again. However, not all solenoids work in a straight line; Rotary types represent other methods of harnessing the electromagnetic potential of the solenoid. However, the principles of the solenoid coil and its function remain the same no matter how the electromagnetic forces are applied.

Most solenoid coils operate in a closed environment, and since they generate a fair amount of heat, the chance of the coils burning out is a constant possibility. For this reason, many devices equipped with solenoid coils feature a modular construction that allows the coils to be replaced if they burn out or otherwise become damaged. In some cases the device may even be fitted with a coil of a different voltage rating if the need arises. However, some solenoids feature coils and cores that are sealed in a closed unit. One of the more well known sealed variants is the automotive starter solenoid used to engage the starter motor gear.

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