We have a full range of single coil, dc and ac and dual coil dc solenoids.
Single Coil Solenoid
A solenoid is a device that converts electrical energy into mechanical work. Solenoids are made up of a free moving steel plunger that sits within a wound coil of copper wire. When electric current is introduced, a magnetic field forms which draws the plunger in. The exposed end of the plunger can be attached to equipment, and when the solenoid is activated, the plunger will move to open, close, turn on or turn off that equipment. Single coil devices are generally safer to use since the current required is low, but single coil devices are bulky.
Dual Coil Solenoid
To allow a solenoid to be held energized for long periods of time without overheating, two separate coil windings are used instead of one. The first coil operates at a high current level to provide maximum pull or push. The second coil simply holds the plunger in place after it has completed its stroke. Since the current required to hold the plunger in place is low, Dual coil solenoids can be energized continuously without overheating. This design concept results in a highly compact solenoid approximately 1/2 the size of a comparable single coil unit. After energizing and pulling the plunger, the pull coil must be turned off as soon as possible to prevent overheating or burnout.
Solenoid Selection Factors
- The pull or push force required to move the plunger and load from a de-energized or non-voltage position to an energized or voltage induced position.
- The force required to hold the plunger and load in its energized or voltage induced position.
- The total distance or stroke the plunger travels when the solenoid is energized.
- All solenoids are affected by temperature. The hotter the solenoid, the less work it can do because the copper coil wire resistance changes.
- Low voltage also reduces the solenoid’s work output.
- Location : Although the solenoid is designed to operate in harsh environments, locations with excessive heat buildup and constant exposure to liquid and particulate contaminants should be avoided.
- Brackets : Must be sufficiently strong to handle solenoid pull force, vibration and shock inherent in the application.
- Alignment : The solenoid should be mounted so as to permit the plunger to be linked in a direct line to the load. Misalignment causes side loading and resulting friction reduces the available force.
- Solenoid position : The solenoid should be oriented with the plunger pointed vertically down or at some downward angle, to avoid collection of contaminants in the plunger bore.
For the internal switch to automatically disconnect the high current pull coil, solenoid linkage systems must allow the plunger to move completely into solenoid body and bottom out without binding. Failure to bottom out will cause an internally switched solenoid to burn out and an externally switched solenoid to drop out.
Plunger travel should also be checked and limited to the solenoid rated stroke.
To minimize voltage loss and resulting force duration, the proper wire thickness based upon total wire length from battery to solenoid and current rating of the solenoid, should be used.
A partially discharged battery will result in malfunction of dual coil solenoids, due to insufficient, but still high energizing current, which prevents the energizing coil from switching off, thus causing burnout.
To protect solenoids from permanent damage due to overload and overheating, a well designed system will always include an overload protection device such as a slow blow fuse or a slow acting circuit breaker.
Solenoids pull and hold cannot be tested when the solenoid is fitted on the equipment, since the setting of the variety of linkages used may also contribute to frictional and force losses. Removing one solenoid and replacing with another will change the settings of the linkages and does not indicate that the first solenoid is faulty.