Test Results Show 18% Reduction In Energy Consumption For 3 Speed Versus 1 Speed EV Transmission

SEP 22 2015 BY MARK KANE 83

Alex Tylee-Birdsall, Managing Director of Evolute Drives

Alex Tylee-Birdsall, Managing Director of Evolute Drives

Evolute Drive, a new company from the UK, intends to present its 3-speed MSYS electric vehicle transmission at the CTI Symposium in Shanghai (16-18 Sept) – and a paper entitled ‘Next Generation Development – MSYS 3-speed EV Transmission’ on 18 Sept at 16:45 in session D.

According to the press release, prototype of MSYS tested independently in a B-class demonstrator vehicle at the MIRA facility achieved up to 18% reduction in energy consumption over the NEDC test cycle compared to a single-speed gearbox.

18% is a significant improvement (even more than the expected 10-15%). But we believe that real world range will increase by less value as the energy savings concerns only the drivetrain specifically.

About the MSYS:

“The cone clutches used in MSYS allow much greater torque transmission density than a wet multi-plate clutch, providing over four times the torque capacity within the same package size. Recent developments include minimising torque oscillation during engagement to ensure good and consistent shift feel, through the management of concentricity of the assembly.

The presentation will also describe efficiency improvements obtained through a novel twin-mode lubrication system. The lubricant flow rate to the clutches is increased only during shift events, when greater cooling is required, by a simple variable distribution system. At other times the flow rate is reduced to minimise energy requirements.”

“Production-intent prototypes of the MSYS transmission should complete their testing during 2016 and validated production units are scheduled for sign-off around mid-2017.”

Alex Tylee-Birdsall, Managing Director of Evolute Drives said:

“The results, obtained at the MIRA facility in the UK, endorse our previous expectations of a 10-15 percent improvement when a single-speed drive is replaced by our MSYS transmission. Reducing the energy required by an EV leads to a corresponding improvement in range, which is still a key issue for many EV users.”

“MSYS allows full torque power shifts to be made but requires no energy to hold the transmission in gear, which improves system efficiency. The key to the technology is the separation of the two functions provided by a synchroniser (friction and latching), while enhancing the friction capacity so it can be used to temporarily drive the vehicle.”

Single-speed drive is a brilliant solution for EVs, but 18% more efficient sounds swell too.

There are concerns about reliability and maintenance of EV transmissions that we are unable to settle until someone introduces a non-performance electric car with two or three gears in volume.

There is another side of the equation, which we can handle better. For cars like the Nissan LEAF, 18% is like about 4 kWh more usable energy. At contractual $500/kWh, let’s say batteries would cost $2,000 total. Weight of additional batteries and MSYS will be similar, so manufacturers considering more gears must decide whether to offer a larger pack or a multi-speed transmission – for $2,000? Nissan recently choose to offer some 6 kWh more for total 30 kWh.

Detailed specs:

“E-Machine Type    Axial Flux YASA motor
E-Machine Power    55kW continuous (100kW+ for 60s peak)
E-Machine Max Torque    200Nm @ 4000 rpm (limited by power electronic)
Transmission Ratios
(3 speed)     1st – 9.93:1
2nd – 7.11:1
3rd – 5.08:1
Gear Shift    Hydraulically Actuated Powershift Technology
Driveline Efficiency    98% Transmission, 95% Motor, 97% Power electronics, 91% Overall
Lubrication System    Dry Sump (Light Oil Spray)
Park Lock    Integrated Plunger Type with Electrical Actuation
Powertrain Weight    55kg Prototype Unit (wet) 45kg Production Intent (wet)
Installation Length    366mm Prototype Unit 320mm Production Intent
Cooling System    Pump and In-built Sump Radiator
Options    Output disconnect for e-AWD application”

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83 Comments on "Test Results Show 18% Reduction In Energy Consumption For 3 Speed Versus 1 Speed EV Transmission"

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jelloslug

That seem really high considering the losses in a transmission. The motor they used has a much lower output than even what is in a Leaf so I would really question if it could even hold up over time.

RexxSee

Tesla already solved the problem with two differently gearred motors.

RexxSee

I wonder if a transmission-like effect could be achieved simply by adding and fiddling with the wiring of the motor? Software controlled naturally…

RexxSee

A kind of CVT motor…

miggy

The Outlander PHEV was the first with twin motors and two differently geared motors for all wheel drive.

Bill Howland

Huh?? 98% gearbox efficiency is fantastic. Unless you know the scale of the gearing used, and what “Nema Class” it is running on, that’s just unoriented conjecture.

I notice in my volt, the efficiency drops off unless I start V E R Y S L O W L Y off the line from a standing stop. This transmission, or others like it, should get the motor into its efficient speed range more quickly and keep it there most of the time.

The Voltec rather does some of this already as a CVT, by bringing in the second dynamo when the speed of the first motor is getting too high.

Djoni

I just don’t see 18% gains here.
Total claim efficiency of 91% isn’t 18% better than what we actually have.
The gain seems to be only in the inverter at 97% it probably beat the 90-95% usual numbers, but all of that have to be proven with independent testing.

SJC

A motor may have 90% peak efficiency, but that is not the efficiency across all operating modes. Taking off from a stop takes a large current and has lower efficiency.

Stimpy

A transmission for my EV? That’s a big NO THANK YOU!

Bill Howland

You must not drive a volt. Or an ELR, Or several other PHEV’s that have cvt’s.

Mark C

Back in the day, we converted a ’66 Impala from a powerglide transmission {2 speed} to a turbo 400 {3 speed} and liked the car so much better. Much faster acceleration and better gas mileage driving in town.

It’s always seemed reasonable to me that a multi speed transmission would allow far less starting torque to get the car/truck from a standing start up to driving speed. And if that’s the case, better range should follow.

jelloslug

There is a huge difference between the torque delivery of an electric motor and an ICE. Your experience made the car stay in the usable torque band of the engine longer than the old transmission did. Since the types of motors that are used in EVs don’t work that way the benefits don’t really add up.

Bill Howland

No offense but it sounds as though you are talking through your hat again. Both the GEN 1 and 2 versions of the volt have changeable ratio ‘transmissions’ in them. They also have much more modern motors in them than the 120 year old stuff Tesla has always used.

Pushmi-Pullyu

“Much more modern”? You mean, like the sun and planet gear used in the Volt, which was patented by James Watt in 1781… 234 years ago?

Nah… you’re just trolling.

Bill Howland

In my humble opinion, you have nothing to contribute here. Several knowledgeable people here are annoyed by your lack of intelligent responses, almost all of which are not germane.

Pushmi-Pullyu

It’s certainly not impossible that a production, highway-capable plug-in EV might benefit from having a transmission. But let’s see them demonstrate that they can build one that will stand up to daily use for years.

As many of us know, Tesla tried to use a two-speed transmission in its first car, the Roadster. But after trying two different transmissions developed by two different vendors, they gave up because neither transmission could stand up to daily use.

If (as jelloslug says) the MSYS prototype doesn’t even use a motor as powerful as that in the Leaf, then that’s a pretty strong indication it can’t stand up to the stresses of real-world EV driving in a consumer car.

Bill Howland

More nonsense. You ever hear of a Volt? One has gone well over 200,000 miles. Without a transmission changeout.

ffbj

A well made transmission can last the life of the car if you take care of it.

Pushmi-Pullyu

@ Bill Howland:

Seriously, you think the Voltec powertrain is even remotely similar to an ordinary transmission?

Dude! You really should attempt to learn at least something about a subject before expressing an opinion.

Bill Howland

I’ve designed drives successfully with decent longevity and efficiency. You seem to think, reading between the lines of your commentary, that you think that technological advances only occur within the auto industry. It is rather insulting for the village idiot to tell someone who has successfully made things he knows nothing.

Pushmi-Pullyu

Bill Howland said:

“It is rather insulting for the village idiot to tell someone who has successfully made things he knows nothing.”

I couldn’t agree more.

Cavaron

Mh… better efficiency means less energy consumption. But an additional transmission means more moving parts that can break. I think I would choose a bigger battery instead.

liberty

add a second motor like Tesla in the D, chevy in the volt, and its win win.

I don’t think the old 3 speed or even 8 speed is a good solution on modertn plug ins.

1-speed – simple, reliable, inexpensive
D – AWD and more efficiency
2 motor with universal gear = electronic cvt, best gear always.

Those all seem like better chioces for verious cars than a 3 speed, unless that 3 speed is inexpensive.

ffbj

It does seem the thrust is away from going with a transmission by improving in other areas as you note.

Bob

Sounds like it cost and weigh the same as the batteries it safes… And batteries are getting cheaper and lighter very fast.

jelloslug

Exactly. It might allow you to use a smaller motor but at what expense? I’m sure a 55kw B Class is not going to be very fast at all.

kubel

It weighs close to 100 lbs (not including motor) and I would imagine cost would be $1000 or more. I doubt the 18% figure, but let’s assume it’s true and a 2016 LEAF could get 18% more range if one of theses were installed…

How many kWh worth of batteries can you get with 100 lbs or $1000, and would that give 18% more range? Seems like it would be very close.

I think I would rather keep the simplicity and just have a bigger battery. If we have to replace batteries AND transmissions at 5-8 years, it’s going to make for a very expensive car to maintain.

Ryan H

Great, let’s add more things to our EVs that can break and need regular service… pass.

HVACman

The Gen 2 Voltec twin-motor design, with each motor optimized for a specific speed range + allowing for CVT type behavior to widen the “sweet spots” for each speed band, makes transmissions like this 3-speed obsolete before they even hit the market. I wouldn’t be surprised if GM goes with the twin-motor concept for the Bolt.

DonC

Almost guaranteed the Bolt will have a single reduction gear. It’s more efficient than the Volt setup.

HVACman

I’m still not convinced there isn’t a good case for a twin motor concept in a pure EV, too. GM made much of the fact they were able to reduce motor costs with the twin motor (one uses inexpensive ferrite magnets, one just a little rare-earth) and optimize torque/speed characteristics for each.

Reducing costs + squeezing 10% or more net motor efficiency is a huge gain relative to the extra 2-3% loss from another planetary gear set. With the integrated power electronics concept of the Gen 2 Voltec transaxle, the differential cost between one inverter and two also diminishes.

I don’t know that an off-the-shelf Gen 2 Voltec drive (less ICE) would make sense for an EV, but the concept, mass-produced, still looks attractive.

GSP

That is what GM did for the Spark EV. It has an extremely efficient 1-speed reduction with only one planetary set needed due to the 400 ft-lb motor. Less gear meshes equals greater efficiency.

The Spark electric drive unit looks big enough to use in the Bolt as is, saving GM the cost of developing and tooling another one.

GSP

larry4pyro

I believe one of the main design goal for both the gen 1 & 2 Voltec transmissions is to keep the electric traction motor operating in an RPM range where it’s efficiency is at the highest. Gen 1 did it by using MGA to turn the planetary gear set to allow the traction motor, MGB at optimum RPM. Gen 2 uses two motors for traction, each designed for maximum efficiency at different RPM ranges. Using a different motor to gain 5 or 6 % better efficiency doesn’t really make much sense except for the fact that they could both be made to operate together when maximum performance is required.

IMHO 18% efficiency gain sounds quite high. The electrical efficiency charts published by GM suggests that operating the motor in its sweet spot is beneficial, but not by that high of a margin.

Pushmi-Pullyu

HVACman said:

“The Gen 2 Voltec twin-motor design… makes transmissions like this 3-speed obsolete before they even hit the market.”

I don’t think anyone would claim this MSYS transmission is appropriate for the more complex powertrain of a PHEV. This is intended for BEVs only.

Even a simplified diagram of the Volt’s gearing (more than just a “transmission”) shows it’s more complex than a single-gear BEV’s powertrain:

ModernMarvelFan

That Voltec diagram shows a single planetary gearset.

Often a single speed gearbox also uses a single planetary gearset as well due to its compact design.

DonC

An 18% gain in efficiency would be phenomenal, a equivalent huge bump in the battery size, but it seems very overstated.

The Spark EV is probably the most efficient drive train out there. It’s 80% efficient on the NEDC cycle and 92% efficient on the US06 Cycle. The 18% increased efficiency claim is only for the NEDC. We don’t know about US06. But it seems highly unlikely that even the NEDC claim would hold up. Not all single reduction drive trains are the same, and claiming an 18% improvement without specifying the base drive train isn’t very meaningful.

shane

Tesla tried this with the Roadster, but ran out of time to get the technology right – and reverted to a single speed system. Can we please keep an open mind about this? If a multi-speed system can enhance efficiency, then it will use less KWHs/yr to drive any distance. Isn’t that a good thing? Numerous studies have projected efficiency gains by going from single speed to multi-speed transmissions in pure EVs – but noone – so far – has demonstrated a cost/weight/volume competitive package. Maybe this is it – maybe it isn’t – but can we please keep an open mind to technology improvements.

Dag Johansen

Yeah, I’m skeptical. I suspect that improvement is exaggerated. And if you reduce it to a more real world level, it would seem easier to just increase the battery size.

shane

If I recall electric motor design theory right, they still have regions in the speed/torque map where they have more and less efficiency. If a multi-speed transmission can keep it on it’s optimum efficiency point more of the time, it enhances the efficiency of the system. (You need to look at the overall system, not just each component – AND, having a multi-speed transmission may enable better optimised electric motors if they don’t need to cover an extremely wide speed range). I admit I might be wrong on some of the details, but let’s keep ALL options open to increase the value proposition of electric cars.

Pushmi-Pullyu

There is no question that in theory, a multi-speed transmission could increase the energy efficiency of a BEV. The question is whether that can be achieved in practice.

Here’s an example: In theory, the rotating design of the Wankel engine should make it more energy efficient than a traditional reciprocating cylinder design. But in practice, increased friction in the Wankel design almost completely wipes out the efficiency gain, while making the engine more difficult — and hence more expensive — to design and manufacture.

“In theory, there’s no difference between theory and practice. In practice, there is.”

shane

By all means – ANY technology will need to go through extensive testing before reputable companies will risk their reputation. And, as I said before this option will need to demonstrate to Tesla/GM or whoever’s engineers that it adds value to the car vs. other options. Part of that will be demonstrating the NET gain after considering weight/cost/volume and maintenance cost tradeoffs. Noone said automotive design, test and production was easy.

Kaleb

I would much rather have a dual-motor AWD EV with each axle having a different fixed ratio–one with a lower ratio for acceleration and one with a higher ratio for cruise. Software then selects the motor and driveunit with the best ratio for given conditions.

Dag Johansen

So you want a Tesla.

storky

Who holds the patent on planetary gear-based Constantly Variable Transmissions? These are clutch-less, the gears are always in mesh, there is no significant surge or plunge in torque as the ratios change and have a proven record of reliability. Why not pay the royalty and have a superior transmission?

Pushmi-Pullyu

Patents only last 20 years. Was the design you’re talking about developed less than 20 years ago? If not, then it’s public domain and no patent applies.

Someone out there

18% sounds much. I can see EVs having two gears if they are designed to go very fast. One daily drive gear and one to achieve a higher top speed. We know from the Brammo Empulse that gearboxes doesn’t really do much for normal driving.

ModernMarvelFan

For most EVs, 2 gears are all you need.

SparkEV Driver

As an owner of an Empulse R, I can say the gearbox does a lot for the bike. I get better low end acceleration and a higher top end. The question for the Brammo is that for the same weight and cost, could that have been better accomplished by a larger motor, controller, and higher draw battery back.

I enjoyed the Brammo more than the Zero SR, hence my purchasing decision, but that was not just the transmission.

18% increase sounds huge, it will be interesting to see what independent studies show.

Someone out there

That’s just a post-purchase rationalization bias. If the gearbox did have an impact the Brammo would have far better stats than the Zero while having basically the same raw specs but it doesn’t.

ModernMarvelFan
Wow, I am just shocked at how “close minded” EV supporters are at having a multi-speed gearbox considering how many people here are “early adopters”. Electric motors have far broader torque curves than ICE engine (wider efficiency band), but it still runs out of RPM. So having a 2 speed or even 3 speed is what will make the driventrain more efficient, especially if you want low end performance and high speed efficiency. It is simple math. But the concerns are basically coming down to increased complexity, cost and durability (the often cited Tesla issue). So, let us discuss each. 1. Complexity. The complexity of a 2 speed transmission or even 3 speed are greater than 1 single speed. That is just a fact. But the question is how much more complexity? A 2 speed/single clutch design is actually very simple, potentially only 2 planetary gearset (as opposed to 1 planetary gearset in the single speed) and 1 clutch. Manual transmissions can be make for very powerful cars and can be very reliable over time. So the slight increased parts count and complexity compared with the overall system is really minimal. Combined with the efficiency curves, it can be controlled… Read more »
Pushmi-Pullyu

ModernMarvelFan said:

“The multi-speed transmission can absolutely be made reliabily even with the higher torqure of the electric motors. The often cited Tesla case is a result of rushed design, lack of funding and specific design requirement.”

You’re expressing opinion as if it were fact. Here’s the actual fact: No modern production BEV uses a multi-speed transmission, despite the competition for greater range. So we have pretty solid evidence — not mere opinion — that several different auto makers have decide that a BEV works best with a single-speed fixed gear ratio.

ModernMarvelFan

NOT you again..

Beside Tesla, how many of the so called “modern BEVs” have more than 100 mph top speed with only single speed gearbox?

Tesla only achieved that thru a much larger battery. It is max torque is reached at around 43mph. Its max HP is reached at around 71mph due to gearing. That means that after 71mph, the efficiency of the electric motor is dropping fast.

If Tesla wants 170mph top speed or higher as it can easily support with its battery size, it needs another gear!

Someone out there

Because it doesn’t make sense for a car like the LEAF to be able to go faster than 100 mph. It’s not a race car, nobody has any interest in going 100 mph or more on any sort of regular basis in such a car.

RexxSee

Oh no! Not you again!?!
The much bigger battery of today will very soon be low end material.

Djoni

Well, here you totally missed the point.
Formula E does have gear boxes, but it seems some of the team are going to reduce the numbers of gears this year or at least are trying to.
Just check that and update your info:
http://gas2.org/2015/09/15/williams-boosts-formula-e-battery-power-170-kw-season-2/

Inverter duty driven electric motor can have so much constant torque and power curve if you have the battery to supply all the power that a gear boxes is something rather obsolete that doesn’t provide the advantage claim here for civilian car.
Racing is something totally different as some team could spend thousands of dollars to gain a second or so each lap.
But even there, shifting even electronically, make you lose time.
Everyday driving in traffic, not so much.
I mean, not at all.
With that in consideration 18% efficiency is very doubtful.

Bill Howland
“Not YOU again”, hehe… That guy is usally wrong on electrical opinions, (more than half the time), and now he’s a self-styled big expert on mechanical engineering problems. These people expressing opinions have no knowledge of the various characteristics of the various types of motors available, nor why they act that way. The only ‘orientation’ they have is that Tesla couldn’t get a 2 speed manual gear box to last more than 3 months in a roadster. I more than a little suspect the 14,000 rpm pinion gear and bearings were contributory, but cars have successfully been made with manual transmissions for 1 or 2 years, at least. More like 1 or 2 centuries. Tesla in general has problems with gears as was shown with their “murmuring gearboxes’. They also have problems with doors, mainly with the S, but all the doors tesla needlessly redesigned for the roadster didn’t work. The one lotus door they left unmodified still worked. THis doesn’t mean cars can’t have doors, since apparently only Tesla has trouble with them. So their experience is nothing to hang one’s hat on. Without knowing the “Class” of operation of this new gearbox, I’m not commenting on its longevity,… Read more »
ffbj

I think there is point to questioning as evidence the fact Tesla could not do it right, and thereby concluding it can’t be done.
It was just expedient at the time, to just bypass the problem, as too time consuming to perfect. Does that mean it will not work, no.
But contrariwise it does not mean it will be a better solution, as there will still be trade offs. I am inclined to think an overdrive solution, as you suggest, might be something for the upcoming Roadster to consider.

Pushmi-Pullyu

Bill Howland said:

“That guy is usally wrong on electrical opinions, (more than half the time), and now he’s a self-styled big expert on mechanical engineering problems.”

I have never described myself as an “expert” on any subject related to EVs. Not ever.

On the other hand, one certainly doesn’t have to be an expert to know quite a bit more than a troll who claims to have designed automobile powertrains, yet clearly is lacking in understanding of basic engineering principles.

Bill Howland

I’ve never made, nor claimed to make any automotive mechanical designs. I have made other ‘drives’ both mechanical and electrical. But you go out of your way to be insulting, with the HOPE that you can ‘convince’ the uninitiated. Its an old political game.

It would be refreshing if you could come up with an independent thought not out of wikipedia that happened to be correct. As it is, you are just doing needless mental masturbation.

MMF definitely hit a responsive chord when he said “Not You again”.

Nate

Interesting ideas on both sides.

My non expert opinion, fwiw:

Simplicity of the current BEV’s are a selling point for many.

Going over 100mph is not a big selling point for myself, and I suspect a lot of people.

Increasing range is a selling point. However, it seems flawed if the only focus to achieve that is relying on battery price and capacity improvements. Sure, charging infrastructure could improve to compensate but it seems wasteful to have to depend on that as well. Do all homes have the capacity for higher amp installations installations? Increasing miles of range per minute charged with the existing L2 home evse’s people have (and other public L1, L2, and L3 sites already out there) should also be an objective.

Bill Howland
“…Increasing range is a selling point. However, it seems flawed if the only focus to achieve that is relying on battery price and capacity improvements. Sure, charging infrastructure could improve to compensate but it seems wasteful to have to depend on that as well. Do all homes have the capacity for higher amp installations installations? Increasing miles of range per minute charged with the existing L2 home evse’s people have (and other public L1, L2, and L3 sites already out there) should also be an objective….” Well, while far from perfect, my so-called GEN 1 (meaning old-fashioned) 2011 Volt and 2014 ELR usually are very efficient. As far as infrastructure goes, I only occassionally use 220 volts to charge them at home, using instead the default charger bricks that come with the car at 8 amps. The new National Electrical Code requires a dedicated 20 amp recepticle at each garage stall. Assuming a 2 car garage, 2- 20 amp recepticals could charge FOUR volts at the default rate (16 amps per outlet). So, contrary to needing any new ‘infrastructure’, any new houses have the capability to charge several volts at a time. Even a diminutive patio house with a 1… Read more »
Pushmi-Pullyu

ModernMarvelFan said:

“NOT you again..”

Funny, that was my reaction to seeing your post…

“Beside Tesla, how many of the so called ‘modern BEVs’ have more than 100 mph top speed with only single speed gearbox?”

Well, if we say a top speed of 84 MPH or more, rather than arbitrarily cutting it off at >100 MPH just because that’s three digits, then aside from the Tesla Roadster we get:

Tesla Model S
Tesla Model X
BMW i3
Nissan Leaf
Toyota RAV4 EV
Kia Soul EV
Volkswagon e-Golf
Renault Zoe
Renault Fluence Z.E.

…and every one of these (correct me if I’m wrong) uses a single speed gearbox.

Oh, and the Wrightspeed X-1, a prototype EV racecar, has a transmission locked into a single speed. Also AC Propulsion’s tZero, but perhaps that doesn’t count since it was effectively the prototype for the Tesla Roadster.

Now, the Formula E racecars do use either a 3-speed or a 5-speed transmission, but I doubt anybody is claiming they are more energy efficient!

ModernMarvelFan
Pushim-Pullyu said: “Funny, that was my reaction to seeing your post…” I was hoping for you since you were the one that replied to my post with your usual response that often lack technical substance. Do we need to revisit our exchange on the complexity of the transmission or do I need to re-educate you again on electrical wiring vs. temperature? But those are beside the point. Now, let us discuss the topic at hand here. What you have listed are the cars with somewhat artifically chosen top speed of 80ish mph top speed. Those speed are choosen because 1. they are above normal US legal speed limit. 2. the single gear transmission gear required to have enough low end performance. All of those things you listed are perfect examples of why the single speed transmission is the problem. Sure, they aren’t racing and sufficient for “commuting”. But the problem is that due to extra short gearing used for the low end torqu, the efficiency of most of those motors drop signficantly at highway speed. That is where it would be very helpful to have a much lower rpm on the motor by having an additional gear. I am NOT… Read more »

At what speed (RPM) and torque load can 18% efficiency increase be expected?

ie: at low speed city driving, or with higher speed freeway driving.
Perhaps a simpler & cheaper option is looking at what (fixed) gear ratio best matches typical usage.

Bill Howland

Low Power factor induction motors at high freeway speeds exacerbates electronics losses with all the motors Tesla has used to date (120 year old induction designs).

More modern motors do not have Rotor bar current losses simply because they have no Rotor bar currents.

An overdrive, or other 2 speed transmission would get high speed tesla driving into a much more efficient range for the motor and the drive as a combined system.

Pushmi-Pullyu

Bill Howland said:

“Low Power factor induction motors at high freeway speeds exacerbates electronics losses with all the motors Tesla has used to date (120 year old induction designs).”

Here is some actual history to refute Mr. Howland’s attempts to spread bad memes:

Development of the modern EV powertrain dates from Alan Cocconi’s 1987 development of a greatly improved inverter (more properly described as an integrated motor controller incorporating an inverter), allowing an AC motor to develop high efficiency over a wide range of running speeds. Before that, EVs were generally powered by DC motors, which have a much narrower band of efficient running speeds, and do require a multi-speed transmission to reach highway speeds.

Alan Cocconi worked at GM when he developed his inverter; development of that lead to BEV prototypes which were developed into the GM EV1. After leaving GM, Alan Cocconi became a founder of AC Propulsion, which developed the tZero which was, effectively, the prototype for the Tesla Roadster, which kicked off the modern EV revolution.

While Mr. Howland may be technically correct to say AC motors are “120 year old” technology, that’s as irrelevant to modern automotive engineering as saying the gasoline-powered internal combustion engine dates to 1884.

Bill Howland

I succinctly, accurately, answered a question from Brian Henderson.

ModernMarvelFan

Bill,

you can’t have a technical discussion with people who have no technical background or knowledge.

ModernMarvelFan

I also agree with Bill’s comment.

Most of the motors would start to lose torque and hp at higher rpm due to back-emf issue which is directly related to RPM.

So, to sustain the rpm, a higher drive voltage would have to be supplied which leads to higher loss combined with higher back emf associated with higher rpm. By reducing the rpm at hwy speed, it will reduce back-emf signficantly.

Also, bearings would appreciate the reduction in speed combined with balancing of the motor drive shaft.

You shouldn’t see much difference in low speed when the electric motor are well within its max torque rpm (that is the point where the efficiency starts to drop).

Nathanael

Those “higher rpm” are typically well beyond legal road speeds, so it just doesn’t matter.

ModernMarvelFan

Tesla’s own P85 reaches max torque at 43mph. Is 43mph beyond legal speed?

Tesla’s own P85 reaches max HP at 71mph due to gearing, is 71mph much beyond legal speed? I believe most people would easily drive that today on the hwy.

The arguement here is about efficiency.

Also, premium sedans have much higher speed typically even though they are beyond legal speed in the US.

Bill Howland

Thanks MMF for the support. My point is, if you can slow an induction motor down, and make it take its power at .9 powerfactor, instead of, to use an extreme case, .45 power factor, you’ve just HALVED the current going through the motor windings and HexFets without changing the horsepower output of it. As far as resistance losses go, if you Halve the current you will QUARTER the losses.

They should do an efficiency chart of a Roadster or an “S” on the Autobahn.

Or, on all these drag races they love to do, do an efficiency chart during the first 2 seconds.

I bet it would be an eye-opener.

krona2k

I don’t think this will work out. Batteries are getting cheaper and energy densities are increasing. The added complexity of a multi speed transmission just doesn’t seem worth it.

ModernMarvelFan

battery improvement only helps the issue marginally.

It is the electric motor that is the problem. Higher density battery will allow a higher drive voltage which can overcome the back-emf limited max rpm issue. But it won’t reduce back-emf releated efficiency issue. That is a motor design limitation.

Tomdb

Anyone else realize that the test is in the NEDC cycle.

Requiring no where near 50kw so the motor will be inefficient no matter what gearing. Because the low torque required for the acceleration ramps in the test.

Testing with NEDC cycles gives no relevant comparison to real world driving, you can get a very but very long range with the NEDC cycle in any car. However this is never a real world comparison.

So the gain of 18% sound strange but can be easily explained by the NEDC driving cycle.

Bill Howland

When more and more electric cars turn up with transmissions in them, where is that going to leave all the “BIG EXPERTS” here who say it is impossible for an EV to have a transmission in it?

Companies have gone through the design and manufacturing effort. Don’t you think the thing to do is see why these companies see these devices as so compelling? If they are not needed , or not salable, why bother?

Djoni

Bill, nobody is saying it’s impossible.
But almost everyone is questioning the reason why.
Traditional car manufacturer have been using transmission since the beginning of making car.
But, as you may have note, no one seems to have integrated one in an EV.
If this alone doesn’t tell you they might have rule out this easy and well mastered option in EV because it not necessary, I don’t know what else will.
So unless they’re just all making the wrong decision, it pretty much sum it up.

Bill Howland
“People are questioning why” it is needed? Ok, a bit of background: Back in the heyday of EV’s (and street cars and electric trolleys), vehicles used SERIES-WOUND direct current motors which provided relatively efficient power utilization during startup even WITH power-robbing drop resistances, since the starting torque of the motor would follow the motor current, and the counter-emf voltage would rise, making the efficacious (some use effective, as a misnomer) voltage help the vehicle accelerated. Trolleys and electric trains used AC commutator motors, 25 hz here and mostly 16 2/3 hz in Europe, and ‘suffered’ the same benefits, with reactance drops causing lossless pressure drops, more than compensating for the problems using a ‘dc style’ motor on AC, which is why the low powerline frequencies were used. My information might be a bit dated, but I believe there is still a stretch of 25 hz used in the US. Buffalo was one of the last areas in the US to get rid of general power distribution at 25 hz, around the year 2000, however most new huge cruise ships have very low frequency ac motor drives for the main propeller(s). Small EV kits to this day still rely on DC… Read more »
Djoni

Yes, one simple gear reduction gearboxes does solve this behavior.
Today AC motor can come in three, six or nine phases, and we also over clock motors to 180 Hz in some application so it’s time to get a bit update on that also.
Also inductive and CEMF losses can be controlled to some extend by the inverter modulating the type of wave/frequency you feed the motor.
Even thought that three phases induction motor or permanent magnet seems to be the most chosen so far. (And, in my knowledge with single reduction gear)

Bill Howland

I’m answering the question as to why a 3 speed gearbox would be helpful on an induction motor, say a Tesla Roadster for instance.

Since an induction motor has no inherent torque multiplication as DC series wound motors do as I explained, for 0-whatever acceleration it would be more efficient if the motor could get up to a reasonable speed more quickly.

The second speed would be for normal driving.

The third (overdrive) speed would be helpful, since it would keep the motor speed lower, the powerfactor of the motor higher (which I was trying to explain before the Clown brought in the James Watt irrelevancy), and thereby, not only reduce motor resistance losses but also reduce Power Electronics Module losses due to the reduction of needless, unwanted circulating currents.

Nathanael

Unfortunately, the benefits of having a multi-gear transmission seem to be insigificant compared to the high upfront cost and high maintenance costs.

The torque without it is sufficient for all street-legal purposes, and the efficiency savings aren’t good enough to make up for the additional moving wear-and-tear parts.

Race cars are another matter; they still have transmissions.

Bill Howland

“Benefits… seem to be insignificant.”

Oh?

Topgear was, in my view, wrongly criticized for saying a Tesla Roadster would only go 58 miles.

The running joke I have with my friend Brian is that he PROVED my roadster would only go 58 miles with him driving.

A 3 speed transmission would greatly reduce those losses, and the handicap would only be a 2 % efficiency loss, and a carefully designed transmission can have less loss than the fixed gearing of the original roadster anyway.

The losses of the motor and electronic controller, at very low and very high speeds, are HUGE. A light weight, reliable gear box would do wonders.

Ever ride in a Chevy VOlt? Its noteworthy efficiency is partially due to its changeable gear ratios.

Bill Howland

Let me clear up an ambiguity in the paragraph above. Dc Series wound motors usually DOUBLE the torque, since for a doubling of current you also get double the field at the field coils, so with the armature current doubled you approach 4 times the torque. That’s why DC series wound motors were used in the first place. Acceleration is very ‘current efficient’, or you could call it, a ‘torque-multiplier.’