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From what I've read, that wouldn't be relevant for an electric vehicle, since there is no transmission. Or that might only be for the Tesla.
by scroy 12y ago
From what I've read, that wouldn't be relevant for an electric vehicle, since there is no transmission. Or that might only be for the Tesla.
- zyxley 12y agoLiterally the entire reason for the transmission for a combustion engine is to make the relatively high minimum speed of an internal combustion work for lower road speeds, with the pleasant side effect of increasing torque at low speed. Electric motors have no need for one, because they have both variable speeds and generally tremendous amounts of torque to start with.
- Gracana 12y agoElectric motors tend to have wide useable rpm ranges, but their efficiency varies across the range, so a transmission is still useful. Scroll 2/3 of the way down this page to see a representative brushless DC motor performance curve, for example: http://www.johnsonelectric.com/en/resources-for-engineers/automotive-applications/motion-technology/ec-motor-brushless.html http://www.johnsonelectric.com/en/resources-for-engineers/au...
- mikeash 12y agoAC induction motors (typically what's used in electric cars) have a pretty flat efficiency curve. For example: http://powerelectronics.com/motion-systems/motors-efficiency-and-adjustable-speed-drives http://powerelectronics.com/motion-systems/motors-efficiency... There would be some minor efficiency gains from having multiple gears, but it's probably small enough that it would be hard to overcome the extra losses from having a more complex transmission. Note that technically electric cars do have a transmission. The motor wants to spin much faster than the tires, so you want a reduction gear to let them both live in the ranges where they're happy. It's a single-gear transmission, though, on every electric car I'm aware of.