A classic three-phase 7 horsepower motor can easily be over 100 pounds and is designed to run around 1800 rpm. This higher power density motor delivers this kind of horsepower at almost 5 times the speed. It has different applications and windows of operation so it isn’t an apples to apples comparison. However, the developers do appear to win the bragging rights for the most energy dense motor commercially available.
Launchpoint Technologies website says, “With a total weight of only 1.4 pounds, this motor produces 7 horsepower at 8400 rpm with 95 percent efficiency. At 5 horsepower per pound, this motor has a higher power density than any other motor on the market.”
There are countless applications for this kind of motor such as improvements in battery life in electric cars, electric bikes, electric-powered aircraft and the list goes on.
What makes this advancement possible is the use of the Halbach Array, which is a clever organization of the polarity of multiple magnets to create a very strong field on one side while almost totally negating the field on the other. Here is an old discussion on the Halback Array on Energetic Forum with some references: Halbach Array
Here is an early demo of the Launchpoint Technologies Halbach Array motor:
A very interesting benefit of the Halbach Array is that it defeats Earnshaw’s Theorem which says, “states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges.”
For example, if you took a ring magnet and had another magnet on a shaft in side of that ring magnet, you wouldn’t be able to get it to stay right in the middle even if you spin it – if you were trying to create a magnetic bearing for example.
However, with the Halbach Array, you can. With the clever arrangement of the polarities of various permanent magnets, you can indeed get a magnet to spin inside of this field and maintain stability in the middle without it sticking to any particular spot.