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Tesla Plaid. Two options for three-motor drive layout



Elon Musk promised to provide a 3-motor version of the configuration for Model S, X, Roadster and Cybertruck, but has not yet said how it will look. In theory, there are 2 options for a possible device, and I propose to consider them.

Option number 1




The first option is a circuit where two electric motors at the rear do not have mechanical communication with each other. There is no differential in the rear axle, and its role is played by electric motors, changing the speed on the drive wheels programmatically.

This arrangement of electric motors allows you to implement the control function of the thrust vector of the wheels. This means that in addition to redistributing wheel revolutions in a turn, electric motors can “direct” the electric vehicle’s thrust vector along the desired path by accelerating individual wheels.

Many companies are now engaged in the development of an electric drive with “vectorization” of wheels, but there are few examples of three-engine electric vehicles with a rear “vector” axis of two engines.

One of the most suitable examples of Tesla ... is the Magna E1.



The E1 prototype introduced in 2017 was created to demonstrate the capabilities of separate rear-wheel drive.

This electric car is the usual Tesla S, but with an unusual drive.

Magna installed 3 engines in the car, each of which produces 188 liters. with. which of course is smaller than the Tesla Model S P100D, and at first it might seem like a deterioration in an electric car. Indeed, the power is less, which affects the direct areas of acceleration, but thanks to the “vectorization” of the rear wheels, the car has become more stable in cornering, which allows you to drive with a minimum decrease in dynamics.


In 2018, Magna re-introduced the same electric car, giving it the name etelligentDrive. The purpose of creating this system was to offer it for installation to small car manufacturers wishing to reduce the cost of developing their own electric vehicle.

Magna specializes in creating components and various systems for auto manufacturers and does not plan to produce its own electric car.

The main and probably the most interesting question for this drive is the price.

Here, so far you can focus only on the example of a 3-motor “vector” electric drive for the rally cross-country E.




Thus, STARD plans to supply sets of this drive at a price of € 194,000 for the rally 2020. The

electric drive , as in the case of Magna, will consist of 3 motors, where there is one motor on the front axle and two on the rear. The difference in power and internal arrangement of the kit.

Power - 450 kW (1100 Nm), and inside the back there are 2 electric motors, 2 inverters, 2 planetary gearboxes and a complete cooling package for the Entrire system in one compact cast aluminum housing.

The performance of the STARD electric racing car will be impressive when you consider that in terms of torque the powertrain is capable of gaining a maximum of 0 to 90% in about 32 milliseconds, and electric motors give out up to 14,000 rpm.

In addition to Magna and STARD 3, the motors were tested in BMW and Audi.

In BMW, a prototype was created on the basis of the 5 Series for testing a set of three Power BEV engines. To power the electric drive, a 45 kW h battery was installed in the machine.



The Power BEV power plant has a maximum power of 530 kW (720 hp) and about 1150 Nâ‹…m, which allows the car to accelerate to 100 km / h in 2.8 seconds.



Audi has built a three-engine concept PB18 e-tron for testing , and this year it plans to release this car in a limited series.
When describing a separate drive “one motor - one wheel”, it is seldom when you find mention of the disadvantages of this circuit.

In Porsche Engineering, when testing a 4-motor prototype, there are several shortcomings.

  • it turned out that the great advantage of electric motors is their quick reaction time, sometimes it can lead to undesirable side effects (vibration).
  • it may happen that individual motors cannot transmit the available power, and it will be necessary to reduce this figure for the second engine in a pair.

Perhaps that is why a circuit with 3 motors has now been developed, which reduces the influence of these two drawbacks by half ... but also reduces the potential benefits of a vector drive.

Option number 2




The second option is a scheme where two electric motors at the rear work through the differential in different modes (sequentially or in parallel).

The first example of such a drive is the ESKAM project (Elektrische SKalierbare Achsantriebs Module).



The ESKAM project (electric scalable bridge, Elektrische SKalierbare AchsantriebsModule) in Germany is funded by the German Federal Ministry of Education and Science (BMBF) and jointly implemented by 11 partners (Ebm Erich BĂĽchele Maschinenbau GmbH; Technical University of DĂĽsseldorf, Electrical and Electrical Machines; Groschvpog AG; Automotive Group GmbH; Aalen University of Applied Sciences, General Engineering; Metallurgical Plant Wilhelm Funke GmbH & Co. KG; REFU Elektronik GmbH; Salzgitter Hydroforming GmbH & Co. KG; University of Stuttgart, Institute of Power Electronics and Electric Drives (ILEA); Wilhelm Vogel GmbH Antriebstechnik ; and the Fraunhofer Institute for Machine Tools and Molding Technologies (IWU).

The aim of the project is to limit the weight of the drive to 100 kg. To do this, it is necessary to connect several high-speed electric motors with the corresponding gearboxes and combine them in a common housing - in other words, reduce the size of the drive using the so-called high-speed electronic machines. To solve this problem, electric motors without rare earth metals were used.



Examples of scaling of the ESKAM electric drive. To keep production costs low, the technologies used should be equally suitable for small and large series.

The first prototype was created in 2016.

Structurally, the solution looks like a symbiosis of two electric motors with a gearbox and power electronics in a common housing. This improves energy efficiency and productivity, and also reduces the weight and cost of the drive. The use of fast-rotating electric motors in combination with suitable transmissions also helps to reduce the weight and volume of the system. The housing for integrating the entire drive is made in a lightweight cast version of magnesium, which meets the special requirements for cooling or thermal load of drive components. The four-wheel drive module for the front and / or rear axle consists of two oil-cooled electric motors with gears and electronics. With an output of 2 x 35 kW, it provides maximum torque of up to 2 x 55 Nm at a speed of 6700 rpm. Thanks to gearboxes with gear ratio i:= 19 each drive wheel can reach more than 1000 Nm. “But it is also possible to use the drive module in small series of new vehicles, for example, in urban vehicles or, as planned, in medium-capacity urban vehicles that can deliver up to 1.5 tons of goods with delivery.

The rated speeds of the engines used are from 10,000 to 20,000 rpm. Choked by electronics, this engine reaches a maximum power of 35 kW at speeds up to 20,000 rpm. Since the maximum power for the driving cycle in the upper speed range (> 17,000 rpm) is no longer completely required, this electronics design assumes that the maximum power can be reduced from 35 kW to 29 kW. With modified components in electronics, the maximum power can not only be kept constant, but can be increased even up to 54 kW. The axis module has numerous advantages, such as high power density and very high torque. For drivers, this means very fast acceleration.While most electric motors have a speed of approximately 10,000 to 15,000 rpm, the ESKAM engine (from Groschopp) has a speed of 20,000 rpm with a maximum torque of 45 N · m (33 lb-ft) and 32 kW (43 h.p.).

To save energy, Groschopp plans to increase the amount of active iron used from 150 to 250 mm. “This corresponds to an increase in productivity of up to 50 percent,” emphasizes Wolfgang Pflug. “However, in order to transfer this extra power to the wheel, amplifications are needed in the gearbox and the electronics.”

The ESKAM electric drive uses high-speed synchronous motors with electric excitation and electronic commutation with a squirrel-cage rotor (EEEK).

Production costs for the final drive module will be from 1,000 to 2,000 euros, which is significantly lower than the current average price in excess of 5,000 euros. With components common on the market, the cost budget remains so small that the cost of producing an entire axis for serial production of 10,000 units will be significantly less than 3,000 euros.

The next potential manufacturer of "dual" electric drives is Gravitron.

This company has developed 3 prototypes of such a drive.







There are amateur electric "twin-engine".


As in the first version, in addition to projects and prototypes, in 2020 there will be real examples of mass-produced electric vehicles with 2 motors on one axis.

The first sports electric car from Aston Martin - Rapide E, has a long development history and in the initial plans was to have separate electric motors with "vectorization of the moment", but for many reasons this did not happen.



Instead of separate electric drives, two synchronous electric motors with a total output of 612 hp were installed in the Rapide E. and 950 Nm on the rear axle, which work through the differential in series.
, , , .
Further analogies with Tesla do not end there.

So the developers are proud of the elasticity of the electric drive: from 50 to 70 mph (80-113 km / h), the electric car accelerates in just one and a half seconds.

How can you not recall the Mask with his promise of super acceleration thanks to Plaid?

And also at Aston Martin they promise that Rapide E will be able to run one lap of the Nurburgring in combat mode, while maintaining the performance of the electrical system, which is somewhat reminiscent of the main problem of the sports Tesla on the same track due to overheating of the electric drive.

There is a truth and a main difference - the maximum circulation of Rapide E will be only 155 cars, and this is largely due to the unwillingness of the company to develop this project further, since having the main drawback in the form of a base base for an electric car, the body of a gasoline car is difficult to optimize the location of the main units. It is easier to create a full-fledged electromobile platform for this purpose.

But for Tesla, there is most likely no problem with installing a third engine when using an analogue of the Rapide E drive, and therefore the logical question arises - “will Musk take risks with a separate wheel drive according to option No. 1, if it gives better handling and not acceleration (when that in Tesla just for better manageability they are developing the SpaceX package?).

Or he will take option No. 2 for better acceleration, solving the problem of overheating of the electric motor, and improving the reliability of the drive (failure of one engine is not a failure of the entire drive). And here, of course, it is important to remember that the first who applied the drive with vectorization - Nissan, did not build a single electric car with such a drive for sale, but instead in 2020 showed an electric drive system with vectorization without a separate drive ( e-4ORCE ).

PS - Cars with ICE also had options for driving wheels with engines according to the first and second options.

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