Solenoid, armature length

Status
Not open for further replies.

ccurtis

Well-Known Member
It is well established that the axial force on a solenoid armature is an inverse, exponential function of the distance that the armature protrudes from the coil. This is because of the air gap that exists and changes with that distance.

So, I'm wondering if I make the armature longer than the coil length, protruding out both ends of the coil, but offset from center, does that helps to increase the initial force on the armature since the armature always fills the hole in the coil (no air gap) and the force seeks to center the armature?
 
Would an armature like that even move? An armature that is all ready in the coil would only become magnetized wouldn't it?
 
I think the armature will tend to centralise itself in the energised coil, so that the push-pull effects of the protruding parts will cancel each other out.
 
alec_t said:
I think the armature will tend to centralise itself in the energised coil, so that the push-pull effects of the protruding parts will cancel each other out.
Click to expand...

I may have misunderstood the description, but I took it as the armature was already centralized in the coil, with equal lengths extending out of the coil.
 
I read the OP to mean it doesn't necessarily protrude by equal amounts at the two ends.
 
alec_t said:
I read the OP to mean it doesn't necessarily protrude by equal amounts at the two ends.
Click to expand...

Yes, that is correct. I envision the armature protruding out one end more than the other end initially. I do expect the armature will center itself. My question is about the force of the pull, whether is be greater with an armature so designed compared to typical armature that does not fill the core of the coil, initially at least. I tend to expect the force will be greater, but am somewhat doubtful since I don't know of any solenoids constructed with over length armatures.
 
Last edited:

Guess I'm dense. How can an armature stick out of both ends of a coil without going completely through the coil? An armature that is already through the coil is not going to move.
 
shortbus= said:
Guess I'm dense. How can an armature stick out of both ends of a coil without going completely through the coil? An armature that is already through the coil is not going to move.
Click to expand...

Maybe I am dense and the armature will not center itself because it will not move if it already fills the hole in the coil?
 
If the armature is fully under the coil it will not move. regardless if it is partially centered or not.
Max.
 
ccurtis said:
Maybe I am dense and the armature will not center itself because it will not move if it already fills the hole in the coil?
Click to expand...

Exactly. If the armature is already through the coil, what will cause it to move? It will just make the armature magnetic, as long as the coil is energized. There needs to be a part of the armature that isn't within the coil, to cause movement.
 
Status
Not open for further replies.

Similar threads

Force on armature in soleniod if it is a magnet
Replies
4
Views
6K
Colin
C
A
Solenoid questions...
Replies
6
Views
2K
alec_t
magnetic field generated by circular current loop with N turns and solenoid
Replies
2
Views
2K
MrAl
M
what is so strange about triangle with length of sqrt(2) and circumference of circle?
2
Replies
24
Views
6K
MrAl
M
S
Solenoids: Turns, Current, Voltage, and general confusion all around
Replies
9
Views
27K
MrAl
M
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…