Air Gap

A low permeability gap in the flux path of a magnetic circuit. Often air, but inclusive of other materials such as paint, plating material, plastic, etc.

In a linear solenoid, often the dominant part of the air gap is the distance between the front end of the actuator (plunger) and the bottom end of the solenoid (end core), also referred to as the STROKE.



Ampere Turns

A term that relates to the force produced by the solenoid or electromagnet which is the product of the current passing through the coil multiplied by the number of turns of wire inside the coil.

The force of a solenoid is generally defined as Ampere Turns which resembles a graph that changes its value as the stroke changes.

For each device the value of Ampere Turns is limited by the Duty Cycle.




The moving part of a solenoid. In a linear solenoid this part is also referred to as the plunger.




Same as Ampere Turns.




The spool, usually made of plastic, on which the magnet wire is wound.



Duty Cycle

Duty cycle is the ratio of "ON" time over the "ON + OFF" time ("TOTAL" time) for any one cycle of operation. Duty cycle is usually expressed in percentage.

For example, the duty cycle of a solenoid being cycled "on" and "off" at the rate of 2 seconds ON and 18 seconds OFF is 2/(2+18)= 1/10 or 10%.

The duty cycle for a unit being left in the ON position for an extended period of time (depending on the size of solenoid this could be ranging from a few seconds to a few minutes) would be considered 100% or CONTINUOUS.

As the duty cycle of the application becomes smaller, the allowance for the input power increases. This is because the device is allowed to cool down in between ON times. The increase in input power will result in an increase in force generation.

The specifications in this catalog generally show the force values for duty cycles of CONTINUOUS (100% or C), INTERMITTENT (50% or I), LONG PULSE (25% or L) and PULSE (10% or P).




Life of a solenoid is greatly affected by how it is used in the application as well as the environment in which it is used. Generally excessive friction and impact or an excessive operating temperature may result in a reduction in the life of a solenoid.

To maximize the life, the power input, side load, stroke and attached load as well as the amount of dust or dirt should be kept to a minimum.

It is best, whenever possible, to use a linear solenoid in a vertical position to allow minimum side load due to plunger weight. In addition, this may allow the dust and other particles that have been generated during the operation of the solenoid to fall out of the plunger/bearing gap.



Magnet Wire

Magnet wire is a copper or aluminum wire covered with thin insulation. It is used in the construction of solenoids and electromagnets among other applications. The wire itself is most often copper, but aluminum wire is not uncommon. The insulation material is usually made of thin enamel.



Maximum ON Time

The maximum length of time a solenoid or an electromagnet can be left in the ON position at a given power input. Exceeding this value may cause damage to the device due to overheating.

Maximum ON time overrides the Duty Cycle. The actual ON time of an application should not be longer than the ON time allowed for the operating duty cycle.

For example, if in an application the duty cycle is 25% and the allowed ON time is 10 seconds, while the actual ON time is 15 seconds, then a longer duty cycle, perhaps 50%, should be considered to ensure that the allowed ON time is not exceeded.




The moving part of a linear solenoid.




The distance a plunger must travel before it is stopped.

The starting point is usually defined by the external components within the mechanism outside the solenoid whereas the end (stopping) point is within the solenoid when the plunger reaches the bottom of the solenoid and cannot go any further. This is for both pull and push type linear solenoids.

In general, the force initially developed by a linear solenoid (starting force for both pull and push types) is dependent upon the stroke; i.e., the longer the stroke, the smaller the force.

Most solenoids listed in our catalog have "non-captive" plungers (unless specifically noted as having a "Captive Plunger"). This means that the plunger is free to move outward within the solenoid until is is totally removed from the body of the solenoid. (See "Solenoid Construction" for more details.)


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