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Electric Motor choices - rethinking AC induction motors

Discussion in 'Technical' started by Bianco, Oct 10, 2008.

  1. Bianco

    Bianco New Member

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    When discussing the electric motor for an EV or Hybrid, the main two talked about are either Permanent Magnet, or 3-phase AC Induction. Both have drawbacks.

    The "3" phase motor has now expanded to include a new "Multi-phase" AC induction motor that can operate in ways that a 3-phase cannot.

    Example, if using a standard 3 Phase AC electric motor
    Option 1 (Alternator) – High speed, Low torque HS/LT
    Option 2 (Starter) – Low Speed, High torque LS/HT
    Option 3 (Combo) – must be “oversized” to provide both HS/LT & LS/HT (and is therefore more expensive)

    The new multi-phase motor/drive, called Chorus Meshcon, co-opts the harmonics that limit motor performance and that typically cause motor heating. This means a Chorus multi-phase motor can generate far more ‘burst’ and ‘startup’ torque than its conventional brethren, up to ten times the torque of a comparable electric motor. And this torque is the type that is needed for only 10-15 seconds at a time and then only on rare occasions, like when going from a dead stop to joining the highway.

    This improved “torque” is key to rethinking the use of an AC induction motor in hybrid or electric vehicles. Chorus Meshcon accomplishes this greater startup, or ‘burst,’ torque by changing both the layout and the software of a standard AC induction motor, with the software "reconfiguring" the motor on the fly, which enables it to smoothly change from behaving like a high-torque low-speed motor to behaving like a low-torque high-speed motor - all without the need for efficiency-robbing physical gearing. This motor effectively provides a ‘Virtual Transmission’ between high speed/low torque operation and the opposite

    More information on this electric motor can be found at Chorus Motors plc.

    Also, Delta Airlines is going to be putting this motor on their Boeing 737NGs starting 2010 (www.Wheeltug.com)
    The press release can be found here

    This motor also provides some other advantages such as simplifying the cooling system (can be air cooled) and simplifying the transmission, saving both weight and expense.
     
  2. doug

    doug Administrator / Head Moderator

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    Can't decide if this is spam or not. Certainly appears to be directed advertising.
     
  3. TEG

    TEG TMC Moderator

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    Looks like Spam, but I vote it is enough on topic to belong here.
     
  4. mt2

    mt2 Member

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    Agreed. It's written like a press release and Bianco seems to have joined and posted this one post right away. But it's on topic and of interest, so... Oh! I'm so conflicted.
     
  5. domenick

    domenick Nerd

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    I've been wondering about these guys for some months now. I was hoping some one a bit smarter (or a lot smarter) than me would chime in with their thoughts.
     
  6. vfx

    vfx Well-Known Member

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    Tesla has motor patents and may be happy with them but another EV maker might want to investigate this tech.
     
  7. trev0006

    trev0006 Banned

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    #8 trev0006, Dec 11, 2008
    Last edited: Nov 17, 2009
  8. doug

    doug Administrator / Head Moderator

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    Is this a spam account? I deleted trev0006's last post as spam since the username is similar to many others we've gotten spam from.
     
  9. Joseph

    Joseph Member

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    That's a brilliant idea.

    (maybe this also reveals how desperate the air lines are to save a buck or two; at least it's progressive)
     
  10. eamon12345

    eamon12345 New Member

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    Difference between neodymium motors are

    Our presumed spammer says thusly:


    Can someone give a rundown of how the vehicle maker goes about choosing the motor for an EV? You have the Prius with neodymium-iron-boron permanent magnet motor and the tesla roadster using a 3-phase 4-pole induction motor.

    What differentiates the two?

    Thanks
     
  11. TEG

    TEG TMC Moderator

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    The answer is rather involved.


    • Costs.
    • Efficiency at various RPMs.
    • Torque characteristics.
    • Complexity of controller design.
    • etc.
     
  12. vfx

    vfx Well-Known Member

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  13. vfx

    vfx Well-Known Member

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    07MOTOR_CA0-popup.jpg
     
  14. TEG

    TEG TMC Moderator

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    Does anyone want to elaborate more on this question?

    Tesla uses AC induction motors. So does the RangerEV.
    But some other EVs like the original Rav4EV and Leaf use permanent magnet motors.
     
  15. Eberhard

    Eberhard #421 Model S #S32

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  16. vfx

    vfx Well-Known Member

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    How about why does Tesla use an AC motor?
    Brushless and ....?
     
  17. Alfred

    Alfred Member

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  18. stopcrazypp

    stopcrazypp Well-Known Member

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    #20 stopcrazypp, May 3, 2011
    Last edited: May 3, 2011
    http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors

    I think most here probably have read the above article before, but just a quick summary.

    AC Induction:
    + Average efficiency possibly higher (magnetic and conduction losses can be traded off)
    + Better for performance (losses don't necessarily grow with size)
    - Control more difficult (maybe more development costs)

    Permanent Magnet / AC Synchronous / DC Brushless:
    + Peak efficiency higher (Unity power factor vs 85% for induction)
    + Rotor cooling easier
    - Magnets expensive/supply constrained (e.g. China's control)
    - Magnetic losses increase with machine size (bad for performance)
    - Difficult to handle because of strong magnet

    Looking at motors of modern vehicles, PM seems to dominate by a huge margin. Some of these use stock PM motors from companies like UQM. Given the results I think it may be that PM motors are actually cheaper or made in higher volume.

    I think the results also give credence to induction being better performance (probably higher power density). The MINI-E has 150kW (204hp) vs the Active E 127 kW(170hp). The Model S will probably get 300kW with a single relatively small induction motor, while the Fisker needs to use dual UQM 150kW PM motors to get 300kW.

    Looking at future high performance EVs with synchronous motors, they all use multiple motors:
    Audi E-tron Frankfurt 4 motors for 230kW total (57.5kW each)
    Audi E-tron Detroit 2 motors for 150kW total (75kW each)
    Mercedes-Benz SLS AMG E-Cell 4 motors for 392 kW (98kW each)

    AC Induction:
    MINI-E
    Tesla Roadster
    Tesla Model S
    Think City

    PM/ AC Synchronous / DC Brushless:
    BMW ActiveE
    BYD F3DM
    Chevrolet Volt
    Coda Sedan
    Ford Focus EV
    Fisker Karma
    Mitsubshi iMIEV
    Mercedes-Benz A-Class E-Cell
    Nissan Leaf
    Renault Fluence Z.E.
    Smart ed
    Tata Intica Vista EV
    Toyota Prius PHV
    + pretty much all hybrids and HFCVs
     

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