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New, efficient motor design

Discussion in 'Future Vehicles' started by lklundin, Nov 12, 2016.

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  1. lklundin

    lklundin Member

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    One Danish and one Norwegian technical publication are describing a new variant of the Switched Reluctance Motor (SRM)
    called the U-core SRM, developed and patented by the Technical University of Aalborg, Denmark.

    The U-core refers to the (for example 3 pairs of) U-shaped stators, which hold the DC-powered windings.

    A new power electronic controller had to be developed, to properly switch the DC between the different
    pairs of windings, in a BEV this controller will connect directly to the battery, without need for a DC to AC inverter.

    Unlike previous SRM designs, the U-core variant gives the motor both less ripple in the produced momentum and increased efficiency over a wide working range.

    Other advantages:
    Uses no rare earth metals, reducing price and risks in supply chain
    Uses less copper in a stator mount, making for a more compact and cheaper design

    Disadvantage:
    Less produced momentum making the motor mostly useful in a multi motor design,
    e.g. as front engine that can work mainly during high speed cruising, or in a one motor per wheel design.

    A 160 mm thick and 310 mm diameter prototype delivers peak torque of 106 Nm at 35 kW power, a power density of 2.9kW/L and an efficiency peaking at 94%.

    English description:
    CIPED | Compact Intelligent Powerful Electric Drivetrain for EVs

    Danish:
    http://ing.dk/artikel/danske-forskere-vores-elmotor-oger-elbilers-raekkevidde-med-fem-procent-188165

    Norwegian:
    Ny dansk motorteknologi kan gi elbiler lengre rekkevidde
     
  2. WarpedOne

    WarpedOne Supreme Premier

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    So, under 5% improvement in range compared with the most inefficient electric motors out there.
    Progress is good but electric motors are already so good that such 'news' just raise FUD how existing tech is somehow not good enough.

    Shut up and build the batteries. There ain't enough of them.
     
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  3. lklundin

    lklundin Member

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    Let me help you out with a few misconceptions:
    1) The demand for and research into batteries and into motors is orthogonal, the advent of one more motor design will thus not impede the production of batteries.
    2) Improved batteries increase the range of a BEV and/or reduces its price. So does an improved/simpler motor. Even a crude google translate of the headlines of the linked reports will communicate the expectation that this improved motor design will increase the range of BEVs.
    3) To really make transportation sustainable, a cheaper BEV than the Model 3 will be needed. For that an efficient, cheap, simple motor made from just iron and (reduced amounts of) copper will be useful.

    So maybe you should reconsider who is spreading FUD - and probably even what that acronym actually means.
     
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  4. david_42

    david_42 Member

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  5. lklundin

    lklundin Member

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    Right. Naturally, I cannot know if Tesla or anyone else would ever have an interest in this design. However, if it were to be used in a one motor per wheel vehicle, as I mentioned, the torque could be transferred via a shaft avoiding the drawbacks that you mention. Replacing a single axle + motor with two shafts + two motors would have the advantage of torque vectoring, and controlling those two motors electronically would not be hard.
     
  6. Brando

    Brando Active Member

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    Obviously, a long road from lab to production.
    Consider recent history of Tesla starting with AC Induction Motor (controller software no small accomplishment)
    and now model 3 using PMAC Induction Motor - PM=Permanent Magnetic - right??
    Anyway, seems Tesla very concerned about efficiency and will/is watching all electric motor developments I'm sure.

    PS - Tesla mentions using torque steering on Roadster 2020 (2 rear and 1 front motor) as I remember.
     
  7. Rowan256

    Rowan256 Member

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    Another downside is that it can't be used as a dynamo any more, which is often very usefull for a car.

    It would be very nice for boats, garage doors, perhaps even planes and name it, just not for cars.
     
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  8. Brando

    Brando Active Member

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  9. R.S

    R.S Active Member

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    #9 R.S, Feb 8, 2018
    Last edited: Feb 8, 2018
    Like most SRMs it still lacks the power density. It's good for a SRM, but probably hand wound with all the tricks pulled to make it as good as possible.

    To have a comparison:
    A very good IPM from Siemens, with the same diameter but twice as thick can achieve 260 kW and 1000 Nm continuously. Now not all synchronous machines are that good, but that's what's achievable.

    This motor has 17.5 kW continuously. If you scale it up to twice the size, it's still less than 15% of the power density of the Siemens motor.

    A regular IPM would have less power density than the Siemens Motor. Probably only have of it. Still that's 3 times as much power in the same volume.

    So I don't think it will find a lot of use in cars. Multiple motor cars(3-4) are a luxury and it has too little power for that and it's not powerful enough for a single motor vehicle.

    Maybe as a secondary motor in an AWD EV.
     
  10. R.S

    R.S Active Member

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    A SRM can work as a generator as well. You don't need magnets in the core.

    I guess it's a bit harder to imagine, since reluctance is harder to grasp as a concept, but if an electric machine can work as a motor, it can also work as a generator, by definition.

    But it won't work if turned off, you need to bring up reactive power, which again is a hard concept to grasp. Basically you need current flowing in the windings to induce a negative voltage, which therefore is a regenerative power.

    Switched reluctance machines are actually sometimes used as generators, they have for example been used in some wind turbines.
     

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