GM-VOLT : Chevy Volt Electric Car Site

[ad#post_ad]A significant focal point of the Chevrolet Volt launch debriefing that I attended focused on detailing the inner workings of the car’s electric drive unit. This has been dispersed across the Internet often inaccurately and to much controversy that’s rather unwarranted.

I was one of a handful of journalists that attended a presentation by Larry Nitz, GM’s executive director of EVs and hybrids, in which he fully explained the way the system works.

The system was first designed in mid-2007 at which point GM decided to build what up to then was only a concept Chevy Volt. The patent was applied for around that time, and only two weeks ago the company was advised the patent was awarded.

The key components are the 111 kw electric motor, the 55 kw electric motor/generator, and the 62 kw 1.4 L gasoline engine.

The core element is the large electric motor which always turns the driveshaft. The car is always electrically driven. The motor turns the sun gear of a planetary gearset which itself is then connected to the driveshaft through two sets of gears set at a 7 to 1 combined gear reduction ratio. In this state of driving the generator is used to only recapture kinetic energy during motor braking and coasting which is then fed back into the battery. It is grounded to the crankcase by one of three clutches.

The next drive state occurs when the car is still in EV mode, but reaches around 70 mph. At that point the 111 kw electric motor begins to spins too rapidly and loses efficiency, around 6500 rpm. To improve efficiency the system kicks in the smaller 55 kw electric motor to operate in parallel. GM thought a lot about this element and considered instead adding a second gear, but figured they could simply use the generator because at these speeds, “it’s not doing anything, ” said Nitz. “It’s just along for the ride.”

It does so by releasing a second clutch, disengaging the ring of the planetary gearset from its formerly fixed position against the case, which then causes coupling of the generator into the ring gear of the planetary. The parallel input from the smaller motor then allows the RPMs of the larger motor to be reduced, improving the overall efficiency of the system. By allowing the second motor to participate, engineers gained an additional 1 to 2 miles of electric range.

The third state of the system occurs when the battery state of charge drops to a 20 to 25% state of charge, and extended range or charge-sustaining operation commences. There is still a buffer in the battery used to handle the dynamic responses of the vehicle in this mode.

At low speeds, the gas engine comes on board and spins the generator motor simply to produce electricity sufficient to supplement the battery and supply the electric motor. The engine is locked to the generator through a third clutch, and the ring gear stays grounded to the crankcase. GM calls this a weak one motor series that is battery dominant with the engine in the background picking up the average amount of energy the vehicle needs.

The fourth and controversial state commences when the vehicle reaches speeds of 70 mph while in extended range mode.

As in EV mode the ring gear is decoupled from the case by the clutch and the smaller electric motor is once again allowed to operate in parallel with the large motor, increasing the system’s efficiency. The difference here is that the smaller motor is still being turned by the engine and not electricity. Thus the engine becomes coupled with both electric motors and all three work together to turn the driveshaft. Thus the gas engine participates in turning the wheels mechanically although indirectly. The generator is decoupled from the ring gear again when speeds drop back below 70 mph.

Thus although the engine generator can participate in mechanically driving the wheels it never does so directly or in isolation, at all points in time the large electric motor is the main driver of the wheels.

By adding this element, engineers were able to improve fuel efficiency by 10 to 15%.

There has been considerable blogospheric controversy over this as this appears to contradict GM’s previous statements that the engine never drives the wheels. Nitz said GM had to be coy about this element due to intellectual property reasons, and now that the patent has been awarded can finally be more transparent.  He still says there is no solitary direct mechanical drive because to do so would require a clutch to the sun gear decoupling the 111 kw electric motor, something that doesn’t exist and doesn’t happen.

Does this element play a major role? It depends how often you drive over 70 mph and extended range mode.

Next question. How important is it to you?

See a video of Mr. Nitz’ whole presentation here.

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[ad#post_ad]GM is taking the next critical step to position itself competitively in a future of electrified automobiles.

Vice Chairman Tom Stephens is announcing today that GM is expanding its in-house core competency to include the design and manufacture of electric motors. This will make the company the first major US automaker to mass produce its own electric motors.

Electric traction motors are a critical component for both hybrid and electric cars. Stephens likens them to the combustion engine, and the battery to the fuel tank. “In the future, electric motors might become as important to GM as engines are now,” Stephens said.

Doing this development and production in-house will allow the company to improve quality and reliability while at the same time reducing costs.

The first vehicle to launch with a GM-built electric motor will be the next generation rear-wheel drive 2-mode hybrid expected to arrive in 2013.

“Electric motor innovation supported the first wave of automotive growth a century ago with the electric starter, which eliminated the need for a hand crank, and revolutionized automotive travel for the customer,” said Stephens. “We think the electrification of today’s automobiles will be just as revolutionary and just as beneficial to our customers. Electric motors will play a huge role in that.”

GM has already gained considerable experience designing and building electric motors during the last seven years, and over that time has spent $44 million dollars quietly building up expertise and competence.

The new electric motor production project will receive an investment of $246 million which will go towards converting the Baltimore Transmission plant in White Marsh, Maryland into a mass production high volume electric motor plant.

GM says it will build some but not all of its electric motors, but also claims their expertise will better help them better understand the supply chain and to become better customers for buying some motors from outside suppliers.

Pete Savagian is GM’s Engineering Director, of Hybrid Powertrain Systems.  He notes that electric motors are made up of a few core elements, including steel, wire, magnets, bearings, mountings, and cooling systems.  H explains that it is important to optimize these elements to create motors that have high power density, low cost, and excellent longevity and performance. Reducing noise, vibration and harshness is another major tactic for improving customer satisfaction.

This new electric motor core competency and assembly plant adds a new thrust towards the goal of electrification of the automobile in addition to GM’s already operational Brownstown Volt battery pack assembly plant.

Make no mistake about it, this time the electric car is here to stay.

Chevy Volt Powertrain

[ad#post_ad]It may surprise you that considering how important the Volt is to General Motors, the company does not build its electric motor.

Clearly GM played a major role in designing and engineering that motor as it appears to be unique in the industry. It is actually composed of two motors.  The more powerful one acts as the primary driver traction motor, and the other acts as a generator to retrieve kinetic energy during braking and coasting. At times, if needed, both motors can act in parallel, and the system has an electronically limited 111 kw maximum output (150 hp).

The company supplying the Volt motor to GM is unknown. “We haven’t announced that yet,” states Volt spokesperson Rob Peterson.

GM is very serious about the future of electric cars, and doesn’t plan to source its motors indefinitely.

According to a report in USA today, later this month GM will be announcing plans to build or operate its own plant to build motors for electric cars. This announcement will possibly take place at the Washington DC Auto Show which opens on January 27th. Likely the DC initial market announcement will be made then as well.

GM already has opened its own battery assembly plant. Electric motors, according to GM vice chairman Tom Stephens is the “second leg of the stool” for electric cars.

The third leg is the power electronics that control the manner in which the battery and the motor interact.

Stephens didn’t specifically say if GM plans to build those in house as well, but presumably they will.

“Electric motors, batteries, power-control electronics — you need core expertise in those,” he told USA Today.

Source (USA Today)

Mike Allen is the senior automotive editor for Popular Mechanics. In a new article he seems to take issue with Detroit’s strategy that plug-in hybrid vehicles have powerful powertrains. He is in fact taking aim at the Volt.

He invokes images of the famous VW (hippie) microbuses that had 40 hp engines, and recommends that PHEV’s would be better off emulating them.

He recommends PHEVs use a 10 hp microgenerator that could propel highly aerodynamic cars at 60 to 70ph when the battery is drained, and be able produce heat, so that energy of heating the car won’t have to be drained from the battery.

We don’t know the final specs of the Volt’s on-board ICE , but we do know it will be a ‘family zero’ 1.0 L engine with 3 or 4 cylinders turning a 53 kW generator. Of course, the electric drivetrain motor is powerful, giving 0 to 60 of 8.5 seconds and peak speed of 100 mph.

GMs argument is that people still want to maintain and enjoy powerful driving, even when going electric. Allen counters that it may be time for a change in driving expectations in this more energy economical world, aka the VW microbus analogy.

So do we think it would be better to have a smaller on-board microgenerator presumably paired with a less powerful electric engine?

I don’t know about that, but I like the picture that came with the article (above) of the Cont/A123 li-ion prototype pack being raised into the Chevy Volt prototype mule.

Source (Popular Mechanics )

Argonne lab grew out of the Manhattan Project, portions eventually looking at the peaceful uses of the atom. Then the mission became to look at things that are threats to competitiveness of the U.S. economy. The biggest threat right now is recognized as the importation of and dependence on petroleum, with the biggest use being transportation. So Dr. Hillebrand’s lab looks at technology that will enhance displacement of the use of petroleum, and this represents about 10% of Argonne’s overall activity.

His lab is 80% funded by DOE, and 20% through contracts with individual companies. His lab relates to the big three automakers though FreedomCAR, a consortium working to coordinate government and industry resources and efforts. Ideas and challenges, data and information are shared. Some competitive things are not shared, but may be for some individual entities through confidential contracts. In some cases they work with foreign companies as exceptions if they have a technology that will benefit the U.S.

The lab enables the car companies by relating to groups the companies cannot, such as in making fuel economy standards, or giving them access to U.S. grid data. He significantly notes that people should not charge electric cars during the day, that it should not even “enter people’s minds” to top off the battery during the day. He tells us that charging the Volt will have the same current draw as running two plasma TVs for 6 hours. He cautions about maintaining a “slow slide” to the electric car to not overwhelm the grid.

He thinks it could take about 15 years to get to a 5% penetration of the auto fleet by plug-ins.

We talked about GM and the Volt, the idea began 2 years ago. Like everyone else who is very knowledgeable, he is convinced about how real and realistic the program is, and how committed engineers are truly involved.

We also discussed an interesting method Mike Duoba in his lab developed to calculate fuel economy in electric range extended cars like the Volt. In this method the car is driven repeatedly through federal city cycles (6 miles) until the ICE kicks in, then it is driven one more. The fuel economy would then be calculated as the amount of gas used divided by the miles and controlling for electric consumption.

ANL’s site: (LINK)

Part 2 of the interview will be forthcoming

I just had the chance to speak with Nick Zielinksi about the most recent Chevy Volt developments including among other topics, the rationale for recent executive restructuring and a discussion about highway driving range. See video below:

[flash http://www.youtube.com/watch?v=Qk0YOekzhNI]