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Questions about Magnets Answered

Can an electro magnet have more gauss than a neodymium of the same size? 

I was just thinking about robots and advanced prosthetics. One issue with them is they require rather bulky motors to get the lifting and holding capacity we often require. So if power wasn't an issue and you could make a small elecro magnet that has more gauss/a stronger magnetic field than a neodymium magnet. Than we could make strong and smaller motors. 

Just a thought. Discuss!


I think the approach should be different

You say you need bulky motors because of the power required and want to compensate with stronger magnetic fields.

IMHO this is contra-productive.

Take a winch for example: although the motor is quite strong, the main work is done by the planetary gearbox.

If you combine a high speed motor with a worm drive and suitable gear reduction the size of the motor would be much smaller than standard solutions using stepper motors.

The position info can be taken from standard anlge or or rotaion sensors instead through the stepping of the motor.

Just a suggestion though....

I've been thinking on this subject for a bit. If you search online you can come across some interesting projects related to electromagnets. One of which is the Rodin Starship Coil, who some claim has a boosted field. However, most literature on this lacks a lot of citation and experiment comparing normal coils to their rodin coils.

Another issue is the need to shield neodymium magnets from each other. If you clustered a bunch of permanent magnet actuators together (like muscle fibers), they would all stick to each other and make it very difficult to operate.

Lastly, if you want to really use biomimicry to design new artificial motors, you'll need to give up on magnets. Muscle cells employ the attraction of static charge, the same thing that makes your hair stick to a balloon. I've always wanted to experiment with using the triboelectric effect to make new kinds of actuators. Time is short however!

Good luck with your experiments.


4 years ago

Mmmm.... so this is sort of a multiple part question and answer.

Generally speaking, the answer is that electromagnetic coils produce magnetic fields much stronger then any permanent magnet. Since current isn't necessarily limited to spacial confines, pushing current is an easy way to consistently and repeatedly boost magnetic field.

However, when you start looking at a smaller scale, this breaks down somewhat, and not just due to heat. I'll try to explain, but this is not my forte.

Electromagnetic windings conform roughly to the following formula:
B = Magnetic flux density Vector
L = Loop height
m = Magnetic constant
N = Number of turns
i = Current

As the dimensions get smaller, the smaller the loop height and/or the number of turns are. ferromagnetic material does not have that sorta constraint. The magnetic constant, and thus the magnetic flux density, is naturally large.

Finally, you'll notice that current is a variable in the above equation. A permanent magnet produces it's magnetic field without an electrical current. If conserving electricity is a concern, permanent magnets are not a bad thing. This is true in small scale stuff, and in applications where a battery is too heavy.


I guess you would need to experiment with the kind of core material and wire winding combinations. I only heard of small devices like earphones that use rare earth metals for magnets, maybe when scaled up to muscle size they are relatively strong?

HDD also use rare earth magnets in their motors and for the read/write head. A rare earth magnet the size of your fist will crush bone if it's caught between the magnet and a large metal object. I would be interesting to build a motor that uses electro magnets rather than your typical rare earth or farite magnets. Not only would it give you more control over the motor but if the electro magnet could create a stronger field than a typical magnet could then the motor would be stronger and faster.

Guess it's time to wake some winding jigs and see what i can come up with and compare to rating of rare earth magnets of the same size.

Traction motors are typically "separately excited" , with wound field coils.