Electromagnet 12v vs 24v

Hi :slight_smile:

So I am working on a project where I have to pick and place a metal part.
The electromagnet is connected to a 24v robot.

The metal part weights 260g.

My problem is that when using the 24v electromagnet when there is no power connected to the electromagnet the magnet is still holding the item. This does not happen when I am using a 12v electromagnet. Both magnets have a carrying capacity of 20N.

What is causing this, and can it be fixed?

Hope you guys can help :slight_smile:

What is causing this, and can it be fixed?

It is called residual magnitiasm. It is the magnets core becoming permanently magnetised.

Cures are not to run the magnet so hard, you seem to be doing that running it at 12V.
Or demagnetisation of the core. This is best done by reversing the field briefly with a H-bridge. However that might not work and you might have to reverse the field rapidly and repeatedly while at the same time reducing the current to zero.

Remanance and retentivity are other words for this (anything beginning with 'r' seems to be used), one
of the parameters you can measure from a hysteresis plot of a ferromagnetic or ferrimagnetic material.

The electromagnet is clearly either using the wrong metal for its yoke (soft iron is the best material for
low remanance IIRC), or very overpowered for the task.