How Bugatti's New Electric Motor Bends Physics

The engineering of Bugatti's new hypercar pushes the boundaries past what we thought was possible, and despite Bugatti being known for its record-defining combustion engines, the electric side of the all-new Tourbillon is one of the most impressive I have ever seen. The details on their systems aren't openly available to the public, but they have provided some hints that I was able to follow. In this video we'll see some of the incredible engineering of the electric motor and battery that, in the words of the new CEO, helps the vehicle to seemingly bend physics. The path this vehicle is carving for electric propulsion goes far beyond hypercars, and what we'll look at today will be revolutionary for electric flight and much more. Despite the analogue instrument cluster being built by a Swiss watchmaker, the Tourbillon's design is straight from the future. It's also very, very fast, but unlike its predecessor, the Chiron, its powerful engine isn't turbocharged. Instead, over one-third of its phenomenal 1,800 horsepower, or 1.3 megawatts, comes from the electric powertrain. The naturally aspirated V16 engine is augmented by three electric motors, fed by a 25kWh battery. Two of the motors are at the front behind each wheel, with the third at the rear axle. They spin at an unbelievable 24,000rpm and together generate 800 horsepower. To see how this is possible and why it's so impressive, I picked up this old electric motor for us to have a look at. If we look inside this permanent magnet synchronous motor, we can see the rotor which rotates and the stator which stays stationary. The rotor has permanent magnets that want to stay aligned, or synchronized, to the rotating magnetic fields generated by the copper coils in the stator, which act as electromagnets. You can see this in a simplified animation, that shows how the electromagnets on the outside change their state in a rotating pattern to spin the permanent magnets in the middle. As these magnets spin faster and faster, they want to fly out and break free of the rotor, similar to a coin on a spinning plate, or how you feel pushed to the car door as you drive around a corner or roundabout. The forces these magnets feel pulling them outwards gets bigger and bigger as they spin faster, but importantly, this force increases exponentially. This means going from, for example, 1000rpm to 2000rpm, increases the force by 4 times instead of 2 times, and going from 20,000rpm to 24,000rpm increases the force by 50%. This means the Bugatti motor has to withstand unbelievable stresses wanting to pull it all apart. So what are Bugatti doing to overcome these challenges? Well, from what I could find, there's a few tricks they could be using to strengthen their electric motors. The first is one we've seen before, which is to wrap the rotor in strands of carbon fibre. This is done like wrapping string around a spool under tension, then setting the strands in an epoxy. This video shows Sandy Munro examining one from the Model S Plaid. Although this carbon wrap gives significant increases in strength to the rotor, I suspect there might be another trick at play. One possibility is similar to what a team from the University of New South Wales in Sydney have developed. The double-tied arch bridge system is a structural concept that strengthens the arch ribs of a single-tied system using secondary tension tie. Owing to the secondary tension tie, it spreads out the stresses and allows for stronger bridges. When applied to an electric motor, this unique design allows it to withstand higher speeds For the University of New South Wales, this meant achieving a staggering 100,000 RPM in their tests. So that's how the Bugatti Motor could be achieving the mind-blowing speeds without the rotor pulling itself apart. But how are they powering the three of these that they have on board? Of course, from a state-of-the-art battery pack, which has some extra tricks up its sleeve. But before looking at that, if you want to design motors of your own, or anything from propellers to cup holders for that matter, you need to know about today's sponsor Onshape. Onshape is a professional-grade computer-aided design software that is completely free for all makers and hobbyists, forever. It's even free for engineers and companies for six months so they can properly try it out. You can set up everything in two minutes without any downloads and start making stuff straight away, like I've done for so many projects now. Because Onshape is built with a cloud-native architecture, it enables features such as real-time collaboration, seamless integration with mobile and tablet use for iOS and Android, and built-in product data management. The GitHub-inspired collaboration means teams can work more efficiently as new designs can be created without disrupting the main design before being merged in later. File sharing is also as simple as just sending a link, just like the ones down in the description. Onshape is continuously adding new features, so make sure to get a free account and start creating whatever you can think of using onshape.pro.0 which is also down in the description. Now back to Bugatti's new state-of-the-art battery pack. It delivers 800V which is incredibly impressive and up there with the Porsche Taycan, but what's more impressive is how much power it can deliver from its relatively small 25kWh. This 25kWh is about a third the size of a Tesla Model 3 battery, but can deliver over 600kW of power, enough to power a small English village for all of about 2.5 minutes. This ability to provide a huge amount of power from a relatively small battery is referred to as a high power density. What stops a lot of battery packs having higher power densities is either the cell chemistry, or more likely the cooling system, which can't cool down the cells enough without them overheating. The cell chemistry used by Bugatti is likely a specially designed lithium iron phosphate cell, similar to those used in Rimac's record-breaking electric hypercar, the Nivera, or even the extremely power-dense lithium titanate. However, as an engineer that works on the thermal management of electric motors and batteries, I was naturally more interested in how they keep these cells cool. This is where their direct oil cooling system comes in. Instead of trying to cool down the cells by using a coolant liquid that's in a ribbon or a plate that touches the cells, direct oil cooling immerses the battery cells completely. For this to work, a special dielectric oil must be used, meaning it doesn't conduct electricity, so the batteries don't short-circuit. The reason immersion cooling works so well is that the oil can make contact with much more of the battery cells, allowing it to take heat away from it more quickly. Over the years, I've seen a number of research battery packs using dielectric fluids that surround the battery cells to keep them cool, like this one from the University of Warwick on their electric motorbike. However, I haven't seen immersion battery cooling in a production vehicle before. That being said, I have seen something similar being done in electric motors where they use dielectric oil directly onto the windings. Across the world, there's actually a lot of interesting research being done on immersion cooling of batteries. American firm Cargill found that compared to the commonly used contact cooling systems, immersing the battery cells in cooling oil lowered the maximum temperature by 26%. Results showed an incredible 76% reduction in temperature variance across each cell, which is good for safety and lifespan. The innovative science and technology company 3M have also been working on different fluids for use in, among other things, immersive battery cooling, called Novec Engineered Fluids. These are thermally stable, non-flammable, and low toxicity fluids that have shown to be a more environmental option than oil. With all these advancements, immersive battery cooling could become the norm for many ultra-high power applications like hypercars or electric flight. But it is currently more expensive and complex, and could add additional weight to the cooling system. However, it's an area of active research the Bugatti are putting into action. I hope you enjoyed this video and as you're still watching, please consider subscribing. It's free and helps the channel a lot. You might also enjoy some of my other videos, like this one on the genius of contra-rotating propellers. And make sure to check out Onshape using my link onshape.pro.0 and start designing anything. And as always, thanks for watching.