It seems electric motors just needed a push to present amazing technical developments. And that this push came from electric cars. Now we see new concepts fairly often, such as the Magnax motor or the plastic electric motor showed recently and this one, which comes from Texas and Linear Labs. It is called HET, or Hunstable Electric Turbine. And it claims to offer at least two times more torque density than the current top permanent magnet motors in the market.

That is just for starter. Linear Labs also states it has three times more power density and delivers 10 percent more range. The engine would also use 30 percent less copper. And that happens precisely due to the advantages the new motor design offers, according to the company.

Linear Labs calls the HET a “3-dimensional circumferential flux 4 rotor machine”. That begins to explain the differences it has from a regular motor. First of all, it uses four rotors instead of just one or two. 

The stator is fully involved in what the company calls a “magnetic torque tunnel”. With four sides, all of them have the same polarity. And they are “active torque producing areas” that are all in the same direction of the movement.

Linear Labs Present The HET, A Revolutionary Direct-Drive Motor

In other words, “the structure of the HET ensures that all of the magnetic field interactions are fully involved in the production of torque”, according to the company. And that makes it much more efficient at lower RPMs than a regular motor.

What is really innovative about this engine is that, when it needs more power and higher RPMs, it just uses an “electronic transmission” to generate that without losses. And that happens precisely due to the additional rotors.

Linear Labs Present The HET, A Revolutionary Direct-Drive Motor

The main one goes inside the stator and the magnetic torque tunnel. The second one has the form of a plate and is placed on the same axis, apparently fixed to it, but before the main rotor. The third one is similar to the second. 

In the video, it appears both before the main rotor, close to the other plate, and after it, what makes more sense as a rotor meant to seize that side of the magnetic torque tunnel. The last rotor covers the other three and the magnetic torque tunnel. 

Linear Labs Present The HET, A Revolutionary Direct-Drive Motor

The “electronic transmission” consists of mechanically moving the end rotors so that it creates “field weakening”. “By weakening the magnetic fields, excitation speed will increase as torque drops”, states the company.

This is what allows the HET to be good both at low or high RMPs. Normally, induction motors achieve that by reducing the excitation. Permanent magnet motors do that with D axis current injection, basically an opposing current. In both cases, there are drops in efficiency.

Linear Labs Present The HET, A Revolutionary Direct-Drive Motor

According to Linear Labs, their way of creating field weakening avoids that efficiency problem and improves it instead.

That electronic transmission allows a 48-coil, 8-pole, 6-phase HET to simulate three, two or one phases by grouping them. “With the power pulses overlapping rather than being sequential, torque pulsations are noticeably absent and for a given current level, torque is also much greater than conventional machines,” claims the company.


It is possibly due to this system that Brad Hunstable, founder and CEO of Linear Labs, states in this video that the HET is the safest electric motor in the world. According to the executive, it can still work in case some coils are damaged.

Linear Labs also states the HET can work in lower voltages to deliver longer ranges. That’s something similar to what Toroidion promises for its future cars, with the same appeal to safety in case of crashes.


The company has recently obtained $4.5 million in seed funding. If it proves its claims, it will probably see new investors really soon, for the many applications the new electric motor is said to have. And eventually more efficient electric cars as well.

Sources: Linear Labs via Jalopnik and New Atlas

Gallery: Linear Labs Present The HET, A Revolutionary Direct-Drive Motor

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