If I understand correctly, the force (F) versus stroke (x) curve for a solenoid which is open ended (there is no plunger stop in the middle) is something like the curve below:
The plunger is forced to the center of the solenoid where the forces balance and net 0, so there's presumably a point at the axis intersection. I'm interested in what happens at small displacements on either side of x=0.
From informal testing, I believe this is a function of the proportion of plunger length to solenoid length. From my tests done with a plunger which is ~double the length of the solenoid, the peak force occurs when an end of the plunger is aligned with the end of the solenoid as shown:
When the plunger is further inserted there is still a net force acting to pull the plunger to be centered in the solenoid, but it is a smaller force.
My theory is that the force profile in this case is actually something like:
Where the width of the transition region x= +/- ℓ is proportional to how much longer the plunger is than the solenoid. Are my observations above generally expected/sensical? Can I adjust the slope of the transition region by varying this dimension relationship?
I'm also interested in how linear the force curve region of x = +/- ℓ is. How can I predict this region?
Thanks!
