The Californian Lucid Motors is one of the most recent companies added to the industrial automotive scene, however quickly managing to attract attention thanks to the development of futuristic solutions in the all-electric mobility sector. The Air, the only model developed so far by the US company, presents itself as Tesla’s direct rival on the high-performance luxury electric market. Among the many distinctive features of the Air, the extremely compact powertrain stands out, thanks also to the ability of the engineers of Lucid Motors to be able to integrate the differential directly inside the motor generator rotor. The March issue of the magazine edited by Society of Automotive Engineers includes an interesting interview with key figures from Lucid Motors, which revealed more details about the Air’s unique powertrain.
The Lucid Air can count on two electric motors located on the two axes, for a maximum combined power of 805 kW, equivalent to approximately 1080 horsepower. Furthermore, on the EPA driving cycle, Air recorded an autonomy of 830 km, a result of the synergy between the multiple integrated solutions on board, as highlighted by Peter Rawlison, CEO of Lucid Motors: “This milestone is not due to a single factor. It derives from the attention paid to the design of the various systems, earning single percentage points in each area “. Among the many advantages, the Air excels in particular in terms of aerodynamic performance, with the incredible Cx of 0.20, in line with the recently published figures also by Mercedes on the new EQS. To achieve similar aerodynamic penetration values, the engineers of Lucid Motors have done everything possible to guarantee maximum freedom to the aerodynamic department, going to contain the external dimensions without necessarily sacrificing the volumes inside the passenger compartment. Large space was therefore obtained through a design approach aimed at maximum compactness of the powertrain. This shows the organic design of Lucid Motors, in which the powertrain is not aimed solely at the maximum efficiency of the electric transmission, but also at the complete vehicle package, also taking into account the aerodynamic requirements.
Hence the Californian company’s desire to develop its own powertrain at home, as illustrated by Peter Rawlison: “You can’t just buy the technology we have. If I had simply wanted to make another car, I would have trusted suppliers. A lot of new electric vehicle startups or established manufacturers just buy parts. But where is the value of a company that simply buys engines, for example? For some parts of course, we have no intention of reinventing the wheel: Bosch makes a great i-boost braking system; Akebono makes great brakes, while Pirelli and Michelin provide us with excellent tires. But we need to understand the whole system and what the bottleneck is. If we had someone else making the inverter for us, there would always be something we couldn’t control and therefore we couldn’t optimize the whole package. With our technologies we are architects of our destiny“.
Going into the merits of the powertrain, the Air is provided with a 926 Volt battery and a capacity of 112 kWh. However, the main attention was paid to the motor-inverter-transmission package, as explained by Rawlison: “The battery is just the tank for electric cars. The motor and inverter are more important to improve autonomy and efficiency. We have a more efficient engine than any other. We have a more aerodynamic car ”. The Lucid Air has two guide modules, one for each axis. Each module includes an inverter, motor generator and transmission, thus obtaining a remarkable power density. At the rear, the module is also rotated 90 °, so as to lower the external profile so as not to take up space from the luggage compartment without having to impact the external aerodynamics. The big news lies in the differential obtained inside the rotor of the permanent magnet electric motor. The solution was described by Rwalison as a “Single rotational inertia system”referring to the advantage of removing the mechanical couplings with an external differential and with them the efficiency losses linked to the gears.
Although Lucid Motors hasn’t released any pictures or details of their differential crafted inside the rotor, the chief engineer Erich Bach explained the approach behind this solution: “We realized that the center of the rotor was the most logical space for the differentialbecause the center does not generate torque, it is typically a dead mass inside the laminated core ”. Inside the rotor there is thus a differential which, being placed upstream of the reduction gears, works at high speeds but low torques, facilitating downsizing compared to a traditional component. Two shafts emerge from the internal differential on which i are directly affixed planetary gearboxes for the multiplication of the torque, also integrated inside the driving module.
Compactness is also achieved through the design of the cooling circuit. The differential lubrication oil is in fact also used to cool the engine stator. “We found space for the engine cooling channels directly alongside the copperwhere the heat is generated “, Bach explains. “No one else has developed such an engine cooling system, because they thought it would unduly weaken the magnetic field. However, we have cultivated a magnetically dead zone, as we call it, which does not contribute to torque generation. We cool faster than any other. This comes from the simulations we conducted entirely in-house“. In addition to the cooling circuit and the differential, the engine position sensor is also integrated inside the driving module. “It’s all optimized for efficiency. It is not possible to achieve the efficiency we had set for simply by turning to an external supplier. A supplier would not have had the idea of integrating the position sensor with the rotor shaft“. Overall, the single drive module can deliver up to 500 kW of power, equivalent to 670 horsepower, per weight of 74 kg.
The Lucid Air powertrain thus places itself at the forefront of the electric market. There is now great anticipation for future Lucid Motors products, of which Pure, an alternative version of the Air, is expected by the end of the year.
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