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A current article at The Autopian raised an attention-grabbing level in regards to the Kia EV9’s electrical motor. In contrast to most electrical motors, it may change its winding configuration on the fly, successfully doing the identical factor as shifting gears in an ICE automobile. However, to clarify how superb this expertise is, we have to first clarify what transmissions in ICE autos (and a few EVs) do.
Why ICE Automobiles (& Some EVs) Have Transmissions
If you already know loads about combustion engines, transmissions, rear-ends, and wheel sizes, you’ll be able to most likely skip this part. For everybody else, I’m going to clarify within the easiest phrases potential what a transmission does in order that we will examine it to what Kia’s electrical motor does.
Briefly, an ICE automobile’s engine isn’t like an electrical motor the place you’ve gotten on the spot torque out there proper from the get-go at zero RPM. An ICE doesn’t even work at zero RPM, and has to idle when the automobile stops to forestall stalling out. At actually low or excessive RPMs, combustion engines should work inside a reasonably slim band of effectivity, also known as the “power band.” Consider it like pedaling a motorcycle with just one gear ratio; you’d wrestle to begin shifting, and when you’re shifting, you’d both spin out if the gear is just too low, otherwise you’d barely transfer if it’s too excessive. An ICE that’s at too low of an RPM will wrestle to maintain working or get broken.
That is the place the transmission is available in. It’s just like the a number of gears in your bike, permitting the engine to function in its best vary whereas the automobile can go from standstill to freeway speeds. By having numerous gears to select from, the combustion engine can at all times be within the vary of speeds the place it’s comfortable and doesn’t break.
However, to get the very best efficiency and fuel mileage, ICE autos are beginning to include increasingly gears. Fashionable engines do have some flexibility by way of ultimate RPM because of applied sciences like variable valve timing, however getting the entire symphony of pistons, rods, crank, cams, lifters, and injectors to all harmonize across the purpose of creating energy or getting good mileage is loads simpler if you could find the proper tempo.
Some have as many as ten speeds in order that the engine will be not simply in a cheerful vary, however fairly near the best RPM. However, with all of those additional gears comes additional components that may break, finally reaching the purpose of diminishing returns for upkeep, reliability, and value of operation.
Some Electrical Automobiles Have Transmissions, & For Comparable Causes
The common EV nerd who isn’t aware of automotive expertise will let you know that EVs don’t want a transmission. The one-speed gear reducer does the job fairly effectively as a result of fashionable electrical motors work effectively throughout a really big selection of speeds. They’ll work from zero RPM to effectively over 10,000 RPM with out taking harm. Mechanically talking, they’re actually easy, and have solely two shifting components (the rotor and the stator), so there isn’t a fancy symphony to seek out the proper tempo for.
However, an electrical motor’s versatility and suppleness doesn’t imply that it’s obtained the identical energy and effectivity throughout its complete vary of RPMs and pedal positions (torque). There are specific torque and RPM conditions the place an EV’s motor makes energy much more effectively than others, offering for higher vary. There are additionally RPMs and torque conditions the place the motor tends to carry out higher than others.
For that reason, there’s actually no purpose EVs can’t profit from a transmission. Some automakers put easy 2-speed transmissions in manufacturing EVs (the Porsche Taycan is an efficient instance), and other people changing ICE autos to electrical have usually mounted an electrical motor as much as a guide transmission. Jeep has even constructed some electrical automobile prototypes with guide transmissions, which might be enjoyable for lovers.
The actual purpose most EVs don’t do that isn’t that it wouldn’t be good. It’s extra about value financial savings and protecting issues easy. Automakers constructing EVs with a number of drive models have even managed to supply the advantages of a transmission by giving the entrance motor a special gear ratio than the rear one, after which having the pc “shift” between the motors to get higher vary in several conditions. So, the necessity to have the ability to “shift” could be very actual, even for Tesla.
Kia’s Motor Can Shift Its Effectivity Curve With out A Transmission Or A number of Drive Items
Kia managed to discover a artistic workaround for the necessity to shift RPMs to maintain the electrical motor in a pace vary the place it will get probably the most effectivity. And the corporate’s engineers did it with out including in any additional shifting components, like gears or further drive models.
You must learn the entire article at The Autopian in order for you full particulars, however briefly, Kia’s motor is like two motors in a single. Ship the facility into one set of wires, and a you’ve gotten a “wye” motor. Ship the facility into a special set of wires, and you’ve got a “delta” motor. Briefly, the wye configuration tends to work higher at low speeds, whereas the delta configuration is best for larger automobile speeds. It implies that one motor can behave like two completely totally different motors with out the price of an additional drive unit, additional gears, or the rest.
“Shifting” the EV9’s motor is fairly easy: the automobile’s pc sends the facility down totally different wires. Not solely would a driver not want to consider it, they’d most likely not discover in any respect. Throughout my week with an EV9 press automobile, I had no concept something was occurring to ship higher efficiency or vary. It occurs at about 45 miles per hour, with no indication, controls, or shift shock.
The additional advantage is that, just like the Hyundai Ioniq 5 (made by the identical producer), the motor may also be used to transform 400 volt charging to larger voltages to cost the automobile sooner.
This idea of shifting between totally different modes has been round for industrial motors for a very long time, however till just lately, they weren’t very cost-effective to do in EVs. By working with the proper suppliers and benefiting from decreasing semiconductor prices, Kia has managed to carry the idea to the EV world and make it work even higher.
Featured picture by Jennifer Sensiba.
