Shaping The Solenoid Force Curve

Designing the proper solenoid actuator to meet a specific application involves more than just gathering information on required force, stroke and voltage. While these characteristics are certainly the most important, information such as ambient temperatures, environmental conditions and mechanical life required are also necessary in determining suitable performance perimeters for the solenoid being designed.

Solenoid Force CurveA key factor to consider when designing a reliable solenoid actuator is the force vs. stroke performance of the solenoid. Force generation is a function of power input. However, the stroke required also plays a critical role. The solenoids shown in the image to the left each have the same ending hold force once completely energized. The larger solenoid’s stroke is 25mm vs. 3mm for the smaller unit. To achieve the same pull force across the longer stroke, the solenoid’s size must increase to compensate. It may be possible within limits to maintain the size of the solenoid by increasing the power input to get the same force over the longer stroke. However, this can lead to excessive heat generation and increased cost for higher power electronic controls.

When designing the force and stroke characteristics of a solenoid, it is important to understand the point in the stroke where the maximum force of the solenoid will be needed. Just as a compact car and SUV can both carry loads, each has a limit that is tied to a corresponding cost (use of fuel). Solenoids are somewhat the same. Femm PlotMany times the solenoid specified for an application is for the highest force at the longest stroke. This leads to using a larger solenoid than is necessary resulting in increased costs and significant amounts of energy being wasted.

Mapping of the “load” force curve of the application will provide the critical data needed for a more precise design of the solenoid force curve to meet the actual load force at any point along the stroke. This is commonly referred to as “shaping the curve”. Utilizing magnetic analysis software, the design engineer can analyze multiple configurations of magnetic components, non-magnetic components and air gaps in a relatively short time. Design consideration is given to permeability of materials, physical size and configuration of the magnetic and non-magnetic components as well as reduction of air gaps in the flux path. The final design goal is to provide the maximum flux density at strategic points along the stroke length to “shape” the force curve to meet the requirements of the application force. “Shaping” to the most efficient combination of force vs. stroke provides the best optimized solenoid design for size, power consumption and costTypical Solenoid Force Curve.

While we have focused on the significance of “shaping” the force vs. stroke performance of the solenoid, this is just one important factor to consider in the custom design of a reliable solenoid actuator. Environmental factors, mechanical life requirements as well as performance issues pertinent to the specific application must all be considered in the solenoid design. Many times features designed to accommodate mechanical life or environmental requirements such as seals and bushings can adversely affect the “optimized” force vs. stroke performance. Care must be taken when incorporating these features in the solenoid design so that the performance will not be adversely affected.

If you are looking for more information on solenoid force curves, contact our Technical Team to discuss your current or future project needs. TLX Technologies has successfully helped customers improve efficiency, reduce product size and lower power consumption for their applications.

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