Sep 5, 2019 7:15:01 PM
- CGX car nut
- Rennteam Master
- Loc: NWI , United States
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- Registered on: Aug 17, 2011
- Reply to: Wonderbar
Re: Porsche Mission E...the future of Porsche?
Wonderbar:Good information, thanks...
Thanks. One will supplement any technical information on the new Taycan as the information becomes available. It is interesting to compare the electric machines, note it is not motor since all of these devices recuperate electricity as well as provide tractive forces, between Porsche and Tesla.
Tesla originally utilized an AC induction machine, hence its name Tesla, for the inventor of the AC induction machine. While an AC induction machine has high low RPM torque output it has several shortcomings including a costly-to-fabricate copper rotor and decreased efficiency from generating two separate magnetic fields.
Tesla addressed the shortcomings with the Model 3 machine, which is a 3 phase AC 6 pole permanent magnetic switched reluctance machine that is more efficient than the induction device since it only needs to generate one magnetic field. However, switched reluctance machines, which are about 50 years older technology compared with the induction machine, has problems with torque rippling, which can be controlled with permanent magnetic placement and inverter design.
The Porsche Taycan utilizes a third machine design, the permanent magnet synchronous machine, which of course, has other tradeoffs and benefits. However, recall that Porsche has conducted significant research in EV design with its 918 and 919 projects. A couple of distinct differences with the Porsche EV is the use of hairpin wiring, increasing stator wiring densities to stabilize the magnetic field of the machine as well as provides better cooling characteristics than those designs that rely on round wire wrappings. Hairpin wiring designs require additional fabrication costs which increase product price but this is the same type of design used on the LeMans winning racecar where the utmost efficiency was demanded.
Porsche also introduced a two-speed transmission on the rear axle. While some details remain undisclosed, the transmission uses two clutches with the two gear gearset to decrease acceleration times while increasing efficiency during high speed cruising. Another benefit of this system is that the rear machine cane be disconnected from the rear axle by opening both clutches to reduce parasitic inefficiencies from the rotating mass of that machine's rotor. This makes the Taycan a front wheel drive car for most of its high speed cruising regime. It is a similar strategy employed by Audi with its latest Ultra Quattro approach for its ICE cars.
Inverter design is yet another topic; however, not much is disclosed on the approach, beyond the 800 volt battery pack taken by Porsche. One can be assured that Porsche's approach is, with high probability, derived from its motorsports activities.