Motor or solenoid without permanent magnets

Thread Starter

henradrie

Joined Feb 16, 2016
5
I'm trying to find a small motor or solenoid that does not have permanent magnets. I've searched for a while but can't find anything even though I'm sure it exists.

Does anybody know where I could find such things?

The solenoid or motor will be used next to a magnetometer so it can't have any permanent magnets affecting the measurements.
 

MaxHeadRoom

Joined Jul 18, 2013
19,667
Any induction motor does not have P.M.'s. You will have a hard time finding a DC motor with wound fields these days.
Most solenoids are wound, not PM.
Max.
 

GopherT

Joined Nov 23, 2012
8,012
I'm trying to find a small motor or solenoid that does not have permanent magnets. I've searched for a while but can't find anything even though I'm sure it exists.

Does anybody know where I could find such things?

The solenoid or motor will be used next to a magnetometer so it can't have any permanent magnets affecting the measurements.
As sortbus said, a magnetic field is a magnetic field whether it is from a PM or an electromagnet. Are you sure a PM-Free motor will solve your problem?
 

Thread Starter

henradrie

Joined Feb 16, 2016
5
@henradrie, Why would a permanent magnet be any different than the magnetic fields in a wound motor?
Because when a wound motor is turned off the magnetic field disappears and the magnetometer can get its reading. A permanent magnet is always on and will prevent the magnetometer from getting an accurate reading.
 

Alec_t

Joined Sep 17, 2013
10,685
Even without PMs, a motor is likely to have some magnetic remanence. Most steel objects are likely to be weak magnets too.
 

GopherT

Joined Nov 23, 2012
8,012
Because when a wound motor is turned off the magnetic field disappears and the magnetometer can get its reading. A permanent magnet is always on and will prevent the magnetometer from getting an accurate reading.
As long as they are not moving relative to the magnetometer will not cut through any magnetic lines of flux. A stationary metal object (or even magnetic object) should not be a problem. I interested in the details.
 

Kermit2

Joined Feb 5, 2010
4,163
But I too agree, the large mass of electric steel will behave like a weak magnet even with power off. I suggest you look into hydraulic or air, there may be non magnetic types in those forms
 

crutschow

Joined Mar 14, 2008
24,037
As long as they are not moving relative to the magnetometer will not cut through any magnetic lines of flux. A stationary metal object (or even magnetic object) should not be a problem. I interested in the details.
Magnetometers measure static fields.
No movement needed to measure the field.
 

Thread Starter

henradrie

Joined Feb 16, 2016
5
Thanks guys,

I found some solenoids that should work for my application. Even though there will still be some magnetic effects after the coil is turned off they are more manageable than permanent magnets. This should allow us to get accurate measurements of the earth's magnetic field even though we have to compensate.

The solenoids will be mounted on an instrument that goes underground with only one cable connecting it to the surface. All power and communication must be through this single cable. As much as I want to use air that isn't an option.
 
Top