Tesla Roadster – Motor and Transmission
- December 29th, 2009
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Motor
The roadster is powered by a 3-phase, 4-pole electric motor, producing a maximum net power of 248 hp (185 kW). Maximum torque is 200·ft-lbf (270 N·m), obtained at 0 rpm and almost constant up to 6,000 rpm, a common feature of electric motors and one of the biggest differences (from the performance point of view) with internal combustion engines. The motor is air-cooled and does not need a liquid cooling system. The Sport Model introduced during the 2009 Detroit Auto Show includes a motor with a higher density, hand-wound stator that produces a maximum of 288 hp (215 kW). Both motors are designed for rotational speeds of up to 14,000 rpm, and the regular motor delivers an efficiency of typically 90%, or 80% at peak power.
Transmission
Starting in September, 2008 Tesla Motors selected BorgWarner to manufacture gearboxes and began equipping all Roadsters with a single speed, fixed gear gearbox (8.2752:1) with an electrically-actuated parking lock mechanism and a mechanical lubrication pump.
The company previously worked with several companies, including XTrac and Magna International, to find the right automatic transmission, but a two-gear solution proved to be too challenging. This led to substantial delays in production. At the “Town Hall Meeting” with owners in December, 2007, Tesla announced plans to ship the initial 2008 Roadsters with their interim Magna transmissions locked into second gear limiting the performance of the car to less than what was originally stated (0–60 mph (0–97 km/h) in 5.7 seconds instead of the announced 4.0 seconds). Tesla also announced it would upgrade those transmissions under warranty when the final transmission became available.[22][33][61] At the “Town Hall Meeting” with owners on January 30, 2008, Tesla Motors described the planned transmission upgrade as a single-speed gearbox with a drive ratio of 8.27:1 combined with improved electronics and motor cooling that retain the acceleration from 0–60 mph (0–97 km/h) in under 4 seconds and an improved motor limit of 14,000 rpm to retain the 125 mph (201 km/h) top speed.[62] The upgraded system also improved the maximum torque from 200–280 ft·lbf (270–380 N·m) and improves the Roadster’s quarter mile times.