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A latest article at The Autopian raised an fascinating level in regards to the Kia EV9’s electrical motor. Not like most electrical motors, it might probably change its winding configuration on the fly, successfully doing the identical factor as shifting gears in an ICE car. However, to clarify how superb this expertise is, we have to first clarify what transmissions in ICE automobiles (and a few EVs) do.
Why ICE Autos (& Some EVs) Have Transmissions
If you realize so much about combustion engines, transmissions, rear-ends, and wheel sizes, you may most likely skip this part. For everybody else, I’m going to clarify within the easiest phrases attainable what a transmission does in order that we are able to evaluate it to what Kia’s electrical motor does.
In brief, an ICE car’s engine isn’t like an electrical motor the place you have got prompt torque obtainable 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 stop stalling out. At actually low or excessive RPMs, combustion engines must work inside a fairly slender 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 simply 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 operating 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 most effective vary whereas the automobile can go from standstill to freeway speeds. By having plenty of gears to select from, the combustion engine can all the time be inside the vary of speeds the place it’s completely happy and doesn’t break.
However, to get one of the best efficiency and fuel mileage, ICE automobiles are beginning to include increasingly gears. Trendy engines do have some flexibility by way of very best RPM as a consequence 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 aim of creating energy or getting good mileage is so much simpler if you’ll find the fitting tempo.
Some have as many as ten speeds in order that the engine could be not simply in a contented vary, however fairly near the perfect RPM. However, with all of those additional gears comes additional elements that may break, finally reaching the purpose of diminishing returns for upkeep, reliability, and price of operation.
Some Electrical Autos Have Transmissions, & For Comparable Causes
The typical EV nerd who isn’t accustomed to 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 trendy electrical motors work effectively throughout a really wide selection of speeds. They’ll work from zero RPM to effectively over 10,000 RPM with out taking injury. Mechanically talking, they’re actually easy, and have solely two shifting elements (the rotor and the stator), so there isn’t a fancy symphony to seek out the right tempo for.
However, an electrical motor’s versatility and adaptability doesn’t imply that it’s received the identical energy and effectivity throughout its whole 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.
Because of this, there’s actually no cause EVs can’t profit from a transmission. Some automakers put easy 2-speed transmissions in manufacturing EVs (the Porsche Taycan is an effective instance), and other people changing ICE automobiles to electrical have usually mounted an electrical motor as much as a handbook transmission. Jeep has even constructed some electrical car prototypes with handbook transmissions, which might be enjoyable for fans.
The actual cause most EVs don’t do that isn’t that it wouldn’t be good. It’s extra about price financial savings and preserving issues easy. Automakers constructing EVs with a number of drive items have even managed to supply the advantages of a transmission by giving the entrance motor a unique 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” may be very actual, even for Tesla.
Kia’s Motor Can Shift Its Effectivity Curve With out A Transmission Or A number of Drive Models
Kia managed to discover a inventive workaround for the necessity to shift RPMs to maintain the electrical motor in a velocity vary the place it will get probably the most effectivity. And the corporate’s engineers did it with out including in any additional shifting elements, like gears or further drive items.
It is best to learn the entire article at The Autopian in order for you full particulars, however in brief, Kia’s motor is like two motors in a single. Ship the facility into one set of wires, and a you have got a “wye” motor. Ship the facility into a unique set of wires, and you’ve got a “delta” motor. In brief, the wye configuration tends to work higher at low speeds, whereas the delta configuration is best for greater car 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 car’s laptop 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 car, 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 greater voltages to cost the car sooner.
This idea of shifting between totally different modes has been round for industrial motors for a very long time, however till not too long ago, they weren’t very cost-effective to do in EVs. By working with the fitting suppliers and profiting from reducing semiconductor prices, Kia has managed to convey the idea to the EV world and make it work even higher.
Featured picture by Jennifer Sensiba.
