## Electromagnet with 30mA

## Electromagnet with 30mA

(OP)

Hi,

I'm a kind of "crazy inventor", and have now certain kind of "break through" invention on my mind .

I have surfed hours on the web, finding answer what one can get for electromagnet with 30mA and 50-100 turns coil if you can freely select the core material and the shape of core. I have not found the answer. Because the answer is easy to be given for a prfessional, I hope some of you could give it!

"what one can get" equals, more or less to, how big force can be gotten!

Thanks!

Tapio

I'm a kind of "crazy inventor", and have now certain kind of "break through" invention on my mind .

I have surfed hours on the web, finding answer what one can get for electromagnet with 30mA and 50-100 turns coil if you can freely select the core material and the shape of core. I have not found the answer. Because the answer is easy to be given for a prfessional, I hope some of you could give it!

"what one can get" equals, more or less to, how big force can be gotten!

Thanks!

Tapio

## RE: Electromagnet with 30mA

## RE: Electromagnet with 30mA

## RE: Electromagnet with 30mA

thread340-141078

thread340-132216

If you are looking for the equation for force across an airgap:

Force (in Newtons) F = B

^{2}*A/(2*?_{0})where B is the flux density in the airgap (Tesla)

A = area of pole face (or area of airgap in direction perpendicular to flux) (m

^{2})?

_{0}= permeability of free space (=4*pi*10-7)i.e. all in SI units

If you assume a typical flux density in the airgap of 1.0T, you can rewrite this equation as:

force/area = 0.4N/mm²

BUT - to get a flux density of 1.0T for an airgap of 1.0mm, rearranging the equation for reluctance of an airgap (given in one of the above threads) to give ampere-turns:

NI = B*g/?

_{0}where g is the airgap (in meters)= 800 Ampere-turns

Multiply that by 2 (say) to account for reluctance in the rest of the magnetic circuit (>2 if you have another airgap elsewhere) gives 1600Ampere-turns.

I'm afraid you only have 1.5 to 3 A-t from you initial post, so the force you can expect is going to be tiny,

something like less than 1microNewton per mm².

## RE: Electromagnet with 30mA

Let's continue this threat.

How about if I'll use a permanent magnet as an anchor? So the actual force cames from permanent magnet, and the electromagnet is only used as a controller?

Is there any, even hypothetical, way to increase the 1microNewton per mm2 with that kind of construction?

Thanks for your previous answers!!!!!

## RE: Electromagnet with 30mA

http://www.beikimco.com/appguides/actuators.php

Perhaps as you require only a very small displacement, you could employ a step-down geared system.

## RE: Electromagnet with 30mA

try to describe the problem well enough to help finding

a solution.

Plesae read FAQ240-1032

<nbucska@pc33peripherals.com> omit 33 Use subj: ENG-TIPS