Brushless Homopolar Generator/Motor

History & Challenges

The homopolar generator/motor is an updated version of the original Farady disc, it is simple in design but inherently inefficient due to two main factors; generates very low voltages with high current (with only a disc as a current collector so multi turns couldn’t be used to increase the voltage), contact brushes required (so relatively high resistance at low voltage isn’t good and arcing/noise issues with high current draw). Some brilliant minds further improved it including Nikola Tesla (my hero!) with the ‘Dynamo Electric Machine’ and George Forbes with the ‘Forbes Dynamo’. For further reading see wikipedia.

Moving forward almost two hundred years to the present day, for the last couple of years I always liked to ponder on ways to improve it which might make it viable as a motor or generator for modern day uses. Then one night I think I visualised a solution.

Two issues with the original design need to be resolved; 1. to be able to provide a rotor that doesn’t require electrical contact. This can be performed by using a magnetic rotor. 2. is to have a multi turn winding. Both of these changes mean we need to change the motion of the magnetic field from circular motion (which we know doesn’t induce EMF, see Faraday’s paradox) to radial motion, and this might be possible.

A solution I think, to create a magnetic field moving in a radial motion would be to take two pieces of plate made of ferromagnetic material (electric steel or something similar), and to cut out 50 % of the material to give a kind of spiraling vortex pattern in each plate, a bit like the below picture.

Then one of the plates needs to be flipped over to spiral in the opposite way, when placed on top of one another you would get an interference pattern similar to the below picture.