What is a Solenoid?

In essence, a solenoid is a cylindrical coil of wire acting as a magnet when carrying electric current. Trombetta’s Industrial Work Solenoids typically consists of the following main elements:

  • a cylindrical coil,
  • a steel or iron frame or shell,
  • a steel or iron plunger,
  • and optionally, a stationary magnetic pole/travel stop.

A magnetic field is generated within the industrial work solenoid by passing electrical current through the coil. The frame or shell surrounds the coil, providing a flux path. In effect, it focuses the magnetic field produced by the coil. The plunger, being made of highly magnetic material, reacts to the magnetic field by attempting to move to the center of the coil. The plunger will travel to the centered position unless stopped by a load which exceeds the industrial work solenoid's force capability or the plunger contacts the stationary pole/travel stop.


Solenoid FAQs

What do the Wire Colors Mean?
  • White - pull coil/high currrent
  • Red - hold coil/low current
  • Black - ground
What if I have a 2-wire Solenoid?
Non polarity sensitive. Either wire can be hooked up positive to ground.
What is the difference between a Pull or Push Solenoid?
Linear solenoids are designed to pull the plunger with sufficient force to move a connecting load. The same principle can be applied to perform push operation by adding a non-magnetic rod or push bar to the plunger and extending it through the opposite end of the solenoid.
What is Stroke?
Stroke is the airgap between the point where the plunger movement begins and where it seats against a stop. Solenoids will operate at any stroke up to maximum as long as the plunger is seated. Design for the shortest possible stroke for greatest efficiency and minimum wear to prolong service life. Maximum stroke is the longest distance you can effec­ tively operate the solenoid.
What is Force?
You need to make sure your solenoid ratings are appropriate for the worst case scenario. Force curves are in ideal conditions. Low voltage, temperature, side load, vibration can all reduce force output of solenoid including the life of the solenoid.


Force is measured as pounds over the travel distance (i.e.. 12 lbs at 1 inch)
Linkage Alignment Hookup?
The solenoid plunger and the load should be linked in a straight line. Plunger side force results in excess wear of the plunger, guide and a decrease in net force output and life of solenoid.
What is a Control Module?
Trombetta's control module functions as a high current remote coil switching/time delay relay system. When utilized with Trombetta's 3-wire solenoid, it provides a system that can upgrade applications that previously required an internally switched solenoid and/or elaborate wiring methods. Can also be used with 2-wire solenoids externally switched solenoids.
Duty Cycle?
Specifies the length of time a solenoid can be electrically energized and de-energized. There are three categories:
  • Continuous: solenoid on without interruption for long periods of time - usually 10 seconds or longer.
  • Intermittent: coil is ener­gized for a short time, usually not more than 5 seconds and allowing sufficient cooling time before the next operation.
  • Pulse: coil is energized just long enough for the plunger to seat and then must be allowed to cool sufficiently before the next operation.
Formula: ON time/(ON +OFF) time
Example: If a solenoid is energized 1 second out of 4 seconds, the duty cycle is 1/(1+3) = 1/4 or 25%
Rapid Cycling?
Normally, more heat is generated during the actuation period. When rapid cycling occurs, the increase in heat may be more than the solenoid can dissipate even for a continuous duty coil. This will result in reduced performance and could lead to solenoid failure.
Operating temperature?
Coils are designed for a temperature rise of 85 C maximum plus the ambient temperature resulting in total operating temperature. Insulation materials must be selected to provide adequate protection from overheating. Higher temperature insulations are available for extreme operating temperatures. Force measurements stated in our data sheets is when the ambient operating temperature is 25 C. When the temperature rises, the solenoid force becomes weaker. Please take this into consideration when selecting a solenoid.
Environment Protection?
Standard Trombetta units are designed to meet normal industrial application operating conditions. Additional protection of exposed surfaces may be required for unusual situations. Examples are humidity, water splash, oil immersion or spray, sand, dust, dirt, shock, vibration, and radiation.