Ring magnet sliding on iron core solenoid actuator

[xrcv]

Hi everyone, I have lots of (potentially dumb) questions about this "project" I'm working on. It's a voice coil actuator, but with things a bit reversed. Here's how a regular voice-coil actuator is constructed:

The rod that is inside the coil is a magnet and the outer cylinder continues the magnetic path, sort of like an axial horse-shoe magnet. The coil and magnet push or pull each other, based on polarity..

I already ordered a magnet, but in the meantime I found some cheap ring-magnets, still axially polarized, and I'm wondering how well this would work:

I actually already did this experiment with two coils - one loose to slide and one fixed and they did repel or attract each other nicely along the iron bar. With the ring magnet, I suppose the ring and the iron rod inside the ring magnetic fields will move in opposite directions, i.e the iron bar will be "closing" the magnetic field of the ring magnet.

So, then the coil produces a magnetic field and it's either in the same, or in the opposing direction of the field in the rod inside the magnet, moving it left or right..

What I was first wondering is about saturation...If the magnetic field of the magnet saturates the iron rod in it, the magnetic field created by the coil won't be able to "pass" through that point. Is that correct? Or am I wrong?

Can one of the magnetic fields "overpower" the other, so that no linear motion will be efficiently produced? Also, what if I close the magnetic path of the iron rod, would this require less power to produce the same force?

Also I found a thread here:https://www.physicsforums.com/threa...ally-magnetized-permanent-ring-magnet.867355/

that said if the ring magnet is long, the magnetic field near the center will be almost zero. I suppose with an iron rod inside, this is not the case?

Will the force of the movement be linearly proportional to the length of the magnet?

Guess I should just test it, but thought I'd ask before ordering the magnets.

 

[eljose79]

Hi there,

Thank you for sharing your project with us. It sounds like you have some interesting ideas and questions about using a ring magnet in a voice coil actuator. I'll do my best to address your questions and provide some guidance.

Firstly, using a ring magnet instead of a cylindrical magnet in a voice coil actuator is definitely possible. However, there are some factors to consider that may affect the performance of the actuator.

Regarding saturation, you are correct that if the magnetic field of the ring magnet saturates the iron rod inside, it may limit the effectiveness of the actuator. However, this will depend on the strength of the magnet and the size of the iron rod. It's possible that the iron rod may not saturate at all, or only slightly, which would allow the magnetic field of the coil to pass through and produce movement.

In terms of one magnetic field overpowering the other, it is possible for the magnetic fields to cancel each other out if they are in opposite directions. This could potentially limit the effectiveness of the actuator. It's important to carefully consider the strength and orientation of both the ring magnet and the coil to ensure they work together effectively.

Closing the magnetic path of the iron rod may indeed require less power to produce the same force. This is because the closed path allows for a more efficient transfer of energy between the magnet and the coil.

Regarding the thread you found about the magnetic field inside a long ring magnet, this is correct. The magnetic field near the center of a long ring magnet will be close to zero. However, with an iron rod inside, the magnetic field will be affected and may not be zero. It's difficult to say exactly what the field strength will be without knowing the specifics of your setup.

As for the force of the movement being proportional to the length of the magnet, this will also depend on the strength of the magnet and the size of the iron rod. In general, a longer magnet may provide a stronger magnetic field, but it's important to consider all the other factors as well.

In summary, using a ring magnet in a voice coil actuator is possible, but it's important to carefully consider all the factors that may affect its performance. I would recommend testing different configurations and measuring the force produced to determine the most effective setup for your project. I hope this helps and good luck with your experiment!