Voltec drive unit has four basic modes of operation
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Thread: Voltec drive unit has four basic modes of operation

  1. #1
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    Default Voltec drive unit has four basic modes of operation

    I liked their description...because it breaks it down fairly simply info *four* modes...I was not trying to raise the controversy again and bring out the haters/trolls.

    a) http://www.designnews.com/article/51...Efficiency.php

    Electronics Boost Chevy Volt's Efficiency - The Chevy Volt is more than a green vehicle. It's a smart, seamless driving machine that in some cases exceeds the performance of gas-burning cars.
    Charles J. Murray, Senior Technical Editor, Electronics -- Design News, November 16, 2010

    <snip>
    Voltec drive unit now has four basic modes of operation: electric driving (low- and high-speed); and extended range driving (low- and high-speed).

    Here's a quick look at the four modes as described in the article [] are additions:

    Electric Low-Speed [in Charge-Depleting (CD) mode]: The simplest and most well-known of the Volt's four modes, this calls for the vehicle to use the charge from its 435-lb lithium-ion battery pack to power a 111-kW ac traction motor. When the traction motor turns, it transmits power to a sun gear in a planetary gear set, which turns the drive axle. Volt owners are expected to make heavy use of this mode - many will drive the car to work and back, charge it at night, and never use a drop of gasoline in the process.

    Electric High-Speed [in Charge-Depleting (CD) mode]: The Volt typically hits this mode at about 70 mph. Then, the supervisory controller splits the power between the large traction motor and a smaller 54-kW generator-motor (which is still operated by the battery). The planetary gear set blends the power from the two motors and sends it to the drive axle. Even as it switches to this mode, however, the Volt still isn't employing its internal combustion engine - and therefore still isn't burning any gasoline.

    Extended Range Low-Speed [in Charge-Sustaining (CS) mode]: When the battery's charge drops to an unacceptable level, the 1.4-â„“ I-4 engine makes its debut. At low speeds, the engine spins the generator-motor, which replenishes the battery.

    Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split. It calls for power to be delivered through the big traction motor and through the smaller generator-motor. Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency."
    <snip>
    Sidebar:
    So is it an EV? Or a hybrid? To be sure, there's no direct connection between the gasoline-burning engine and the Volt's planetary gear set. Rather, the engine delivers power to the vehicle's generator-motor, which relays it to the ring gear of the planetary gear set. The bottom line is it's not a direct mechanical connection in the manner of a conventional gas-burning car, but the generator-motor arrangement is similar to that of a Toyota Prius, which is a true hybrid.

    Still, GM insists the Volt should still be considered an EV. "It's clearly an electric vehicle," says Pamela Fletcher, global chief engineer for the Volt and for GM's plug-in hybrid electric powertrains. "You can accelerate from a stop to 100 mph and have the engine never come on. You could take the internal combustion engine out of it, and it would drive just fine. But if you took the battery out, it wouldn't drive."

    b) Another excellent article with pictures (thanks WOT and others):
    Chevy Volt Delivers Novel Two-Motor, Four-Mode Extended Range Electric Drive System; Seamless Driver Experience Plus Efficiency
    http://www.greencarcongress.com/2010...-driver-e.html

    c) Deep dive videos: http://www.youtube.com/results?searc...rain+Deep+Dive
    Last edited by scottf200; 10-10-2012 at 10:40 AM. Reason: Add CD and CS standard language; added sidebar and initial haters/troll remakrs

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    I do not like this explanation at all. Misleading at best and wrong in at least one case. Examples follow (and it's not just semantics):

    “At low speeds, the engine spins the generator-motor, which replenishes the battery.”
    I think it is more correct to say: At low speeds, the engine spins the generator-motor. This provides electrical power directly to the traction motor. It also periodically charges the depleted battery just enough to maintain a small reserve for higher power needs, such as hard acceleration.

    “Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set.”
    Now this is just completely wrong. It should say (and herein lies the controversy they refer to): Unlike the other modes, however, this one calls for the internal combustion engine to transmit power directly into a ring gear in the vehicle's planetary gear set.

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    Quote Originally Posted by Shaft View Post
    I do not like this explanation at all. Misleading at best and wrong in at least one case. Examples follow (and it's not just semantics):
    Now this is just completely wrong. It should say (and herein lies the controversy they refer to): Unlike the other modes, however, this one calls for the internal combustion engine to transmit power directly into a ring gear in the vehicle's planetary gear set.
    If you believe the diagrams posted earlier the ICE does not transmit power "directly" into the ring gear but is connected to the motor/generator which in turn is connected to the ring gear. So the ICE, motor/generator and ring gear are connected mechaically as a unit. Then Yes the ICE provides power mechanically to the planetary but thru the motor/generator route.. The question I have and have raised before: does the motor/generator also at this time generate electrical power(from ICE motive power) to drive the large motor? It could very well if the ICE had more power than was required to drive the ring gear at the requested RPM.
    VIN 483 Took Delivery 01/12/11
    (Xzlon = Lives in the forest)

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    How does this explination match-up with this description by GM powertrain engineer Pamela Fletcher? Seems to me the two have some conflicting descriptions.

    http://www.youtube.com/watch?v=343-N...eature=related

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    Quote Originally Posted by Xzlon View Post
    The question I have and have raised before: does the motor/generator also at this time generate electrical power(from ICE motive power) to drive the large motor? It could very well if the ICE had more power than was required to drive the ring gear at the requested RPM.
    It has to, otherwise the 110KW main drive motor has no source of power and it would be a purely ICE driven machine.

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    Quote Originally Posted by larry4pyro View Post
    How does this explination match-up with this description by GM powertrain engineer Pamela Fletcher? Seems to me the two have some conflicting descriptions.

    http://www.youtube.com/watch?v=343-N...eature=related
    Appears to me that Pamela's discription is exactly what I stated. The last diagram she shows also shows a transfer of electric power from the generator/motor to the main motor and battery and since the arrows are double ended, back to the motor/generator from the battery. All bases are covered in this arrangement that has all sections of the drive participating at once. And the software is sophisticated enough to operated the crossovers seamlessly. A Marvel!!!
    VIN 483 Took Delivery 01/12/11
    (Xzlon = Lives in the forest)

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    Quote Originally Posted by scottf200 View Post
    I liked their description...because it breaks it down fairly simply info *four* modes...I was not trying to raise the controversy again and bring out the haters/trolls.

    http://www.designnews.com/article/51...Efficiency.php

    Electronics Boost Chevy Volt's Efficiency - The Chevy Volt is more than a green vehicle. It's a smart, seamless driving machine that in some cases exceeds the performance of gas-burning cars.
    Charles J. Murray, Senior Technical Editor, Electronics -- Design News, November 16, 2010

    <snip>
    Voltec drive unit now has four basic modes of operation: electric driving (low- and high-speed); and extended range driving (low- and high-speed).

    Here's a quick look at the four modes:

    Electric Low-Speed [in Charge-Depleting (CD) mode]: The simplest and most well-known of the Volt's four modes, this calls for the vehicle to use the charge from its 435-lb lithium-ion battery pack to power a 111-kW ac traction motor. When the traction motor turns, it transmits power to a sun gear in a planetary gear set, which turns the drive axle. Volt owners are expected to make heavy use of this mode - many will drive the car to work and back, charge it at night, and never use a drop of gasoline in the process.

    Electric High-Speed [in Charge-Depleting (CD) mode]: The Volt typically hits this mode at about 70 mph. Then, the supervisory controller splits the power between the large traction motor and a smaller 54-kW generator-motor (which is still operated by the battery). The planetary gear set blends the power from the two motors and sends it to the drive axle.Unlike the other mode, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency Even as it switches to this mode, however, the Volt still isn't employing its internal combustion engine - and therefore still isn't burning any gasoline.

    Extended Range Low-Speed [in Charge-Sustaining (CS) mode]: When the battery's charge drops to an unacceptable level, the 1.4 liter I-4 engine (ICE) makes its debut. At normal speeds the engine spins the generator-motor, which provides power for the main drive motor and also replenishes the battery to an acceptable charge level.

    Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split as in the above high speed (CD) mode, but goes one step further. It calls for the Internal Combustion Engine to be connected to the smaller motor-generator and mechanically provide further power directly to the ring gear in the vehicle's planetary gear set while at the same time generating electric power to drive the main electric motor.>
    Sidebar:
    Scott2000,
    I suggest the drive mode descriptions be edited to something like the above editing I have made.
    Last edited by Xzlon; 02-03-2011 at 12:06 PM.
    VIN 483 Took Delivery 01/12/11
    (Xzlon = Lives in the forest)

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    Quote Originally Posted by Xzlon View Post
    Scott2000,I suggest the drive mode descriptions be edited to something like the above editing I have made.
    Can you put your edits in [] so I know what changed? It was a little hard to pick up at several glances. I also change the format in my original post to show it is a quote from the article and where I added []'d info.

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    Quote Originally Posted by scottf200 View Post
    Can you put your edits in [] so I know what changed? It was a little hard to pick up at several glances. I also change the format in my original post to show it is a quote from the article and where I added []'d info.
    Basically I just tried to clarify the extended range descriptions to make them more concise
    VIN 483 Took Delivery 01/12/11
    (Xzlon = Lives in the forest)

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  12. #10
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    Quote Originally Posted by Thread Title
    Voltec drive unit now has four basic modes of operation ?
    ALWAYS DID!
    But the one caveat I is the controversial 2 motor combined mode where ICE is contributing torque to the ring gear (though C2 and C3) is only used when torque demand is relatively light at speeds above 36mph. Under high demand it switches to "pure" series 1-motor electric mode with the power demand handled by the 5 5kW generator and RESS "in tandem" and it operates in this fashion all the way up to maximum speed!
    WOT




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    Last edited by WopOnTour; 12-21-2013 at 02:17 PM. Reason: Added "zoomed view" of powerflow modes

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