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The Electric Scooter: The New Choice for Urban Mobility

Electric mobility promises to become one of the most successful, emission-free solutions for urban areas, ensuring low pollution, low power consumption, simple use, and fast movement. This is confirmed by the growing interest by manufacturers in projects such as KTM.

Harald Plöckinger, a KTM executive board member for production and business development, recently told motorcyclenews.com: “We believe in electro-mobility on two wheels… We are convinced that electric mobility can succeed in urban areas.”

The new generation of electric scooters offers an interesting solution to the issue of recharging the lithium battery. These e-scooters use the energy of the braking system (regenerative braking), which increases their autonomy. USB connectors allow users to connect their mobile devices. There is also flexible support for iPhones, thanks to an app that allows you to turn your iPhone into a mobile information center.

I'm working on a project for the qualification of high-reliability power MOSFETs. The idea is to use FETs as part of a three-phase H-bridge that serves as the core of the motor drive circuitry. Here is a quick overview of some of the important parts.

The bridge is made of three switch branches (A, B, and C). Each branch has two switches (upper and lower). The output (center point) of each branch drives one phase of the electric motor. The two switches of one branch are never turned on simultaneously; this would open a direct path between the DC voltage source (36V) and the ground. Obviously, this would create a very high disruptive current flow (shoot-through). To give an idea of the magnitude of this current, the mean value of the RDS-ON of the MOSFETS is 10mΩ. The current that would flow into the branch, in case of simultaneous turn on, would be:

This is certainly dangerous current value, even if it is a pulsed current.

The path between the DC voltage source and the ground is closed by two switches belonging to two different branches or phases. Current flows from an upper FET to one phase of the motor. The current flows out of a separate phase to the corresponding lower FET to ground. Within the motor, it flows to the corresponding motor brush, through the commutator, and into one rotor winding. The rotor windings can be thought of as rectangular windings that are free to rotate in a fixed magnetic field provided by permanent magnets.

Note that the construction can be reversed — the windings can be fixed as part of the motor stator, and the permanent magnets can be part of the rotor.

A Hall effect sensor senses the position of the rotor. This sensor is part of the control circuitry that determines when the transistors in the three-phase H-bridge turn on and off.

The Hall effect sensor converts the position of the rotor into a voltage signal that is the input of a microcontroller unit that drives the H-bridge. Here is a view of the motor control subsystem.

The e-scooter is an interesting example of electric mobility. This fast-growing technology is very promising for big companies that produce electric vehicles. Have you ever tried an e-scooter? What do you think of electric mobility? Do you think it is a way to reduce pollution in urban areas?

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25 comments on “The Electric Scooter: The New Choice for Urban Mobility

  1. RedDerek
    September 25, 2013

    Just curious why the push for a 3-phase versus a dc motor for the eBike? I am new to the eTransportation method in terms of the electronics and just looking for answers.

  2. Davidled
    September 25, 2013

    Well, in the winter season, tire might be changed to prevent the slip of road. And also, similar to vehicle, engineer might add suspension system which can be adjusted to either soft or hard by switch.

  3. etnapowers
    September 26, 2013

    The reason is mainly because at the beginning these system had been supplied by an AC source that is 3-phase

  4. etnapowers
    September 26, 2013

    Yes I agree on this point, engineers are just working to add some interesting features like the switch you mentioned and for example an array of solar panels to store input charge for the e scooter

  5. samicksha
    September 26, 2013

    Although i dont have much experiance with e-vehicle, but yes i curious understand more on recent devolopment of Fuel Cell and Hybrid, also we in India face problem as high costs and power grid which have contributed to slow sales.

  6. etnapowers
    September 26, 2013

    I think that the actual limitations to this technology will be overtaken if the governance will realize the positive economic impact of electric mobility

  7. Brad_Albing
    September 26, 2013

    @RedDerek – besides etnapowers' answer, the 3-phase motors pack more power per unit of weight. Or higher efficiency, if you want to look at it that way.

  8. Brad_Albing
    September 26, 2013

    @DaeJ – Not sure if you've ever driven a 2-wheeled vehicle (eiher motorized or human powered) in the snow and ice… it's not fun. It can be dangerous — hard to get proper control when slipping and sliding around.

  9. Vishal Prajapati
    September 27, 2013

    I think EV is the next big thing for sure. It is the most promising and clean technology for mobility. Its commercial implementaion has happened in India already. It is best suited for atleast small city rides for sure. I recently met one of the marketing guy from leading EV manufacturer. He had a concern over battery life and its cost. These two are the driving factor of the entire profit making business. At last they has come to a decision to start manufacturing carbon foam batteries instead of Lithium Batteries because of its price benefit.

  10. samicksha
    September 27, 2013

    Yes one of the top challenge is Battery, because batteries in EV need to be able to hold massive amounts of charge to make the EV practical, EV could be less expensive if makers could ramp up production volume with economic cost on the other hand its not easy for makers to counsel consumers, keeping my self as consumer my first question would be how far can i travel with fully charged battery and this question need to be answered….

  11. David Maciel Silva
    September 27, 2013

    Is a trend for the future, electric vehicles ..

    I had the pleasure of knowing a model of Nissan, the LEAF, the big challenge is the cost of the battery is too high to be exchanged. Have you seen any solution for this problem?

    Below the link to the model:
    http://www.nissanusa.com/electric-cars/leaf/

    An alternative are also electric bikes, this will greatly help the environment but will require a readjustment to meet urban demand.

  12. samicksha
    September 28, 2013

    Thanx for the link Maciel, i am big time fan of Nissan and about leaf the best part here is they will give you 8 years battery warranty which i guess was much required to build customer network and confidence in EV.

  13. etnapowers
    September 29, 2013

    The battery is not the only key point for the success of emobility, I believe that a guarantee of reliability will be required to ensure this success.

  14. Netcrawl
    September 29, 2013

    Yes you're right reliability is also  a big concern, but for now the battery get the most attention, there's a great need for a highly innovative products that fits the requirements of hybrid and electric vehicles by reducing their electric consumption by almost 50%. 

  15. Netcrawl
    September 29, 2013

    The industry recognizes the growing potential of electrification of the vehicle propulsion system in meeting carbon emissions target and reduce oil dependency. Although e-mobility is on early stages but we're making huge progress when in comes to increasing battery capacity and cost.    

  16. jkvasan
    September 30, 2013

    The initial thrust needed from stationary position to moving could determine the capacity of the batteries. The initial load could be much more than that would be needed while in motion. It would be interesting to see how the internals of EV are empowered to take this on.

  17. etnapowers
    September 30, 2013

    The managing of the initial load has been optimized in electric vehicles and now it's comparable to that of non electric motors or even better, this is due to a immediate disposal of the power source in the start up phase.

  18. jkvasan
    October 1, 2013

    etnapowers,

    Is it because of some advanced feature incorporated in the motors? Kindly share more details.

  19. etnapowers
    October 1, 2013

    Exactly, there are some electric radar system that are being investigated to avoid collisions, these systems have to be reliable to ensure the overall reliability of the system

  20. WKetel
    October 2, 2013

    The initial load for a scooter is greater than the constant speed load, but not as klarge as it could be for the reason that the scooter must start off a bit gently. A maximum drive startoff could result in a spectacular wheel-stand, which is probably not the intent of most users. In addition, the pulses are current limited by the motor winding inductance, at least for some small period of time. power limiting through pulse width control will be very important in assuring safe operation and maximum battery charge life.

  21. RB3200
    October 9, 2013

    A major problem of battery operated vehicles is that the battery capacity plummets in a real cold climate area. I think for such areas the vehicle would need an alternative power source, perhaps a fuel cell (hydrogen?). For an electric vehicle that fuel cell should then generate electricity, unless it can only work with low efficiency when compared to a direct combustion driven engine with the same fuel. In that case the cold climate users would be better off buying a fuel cell vehicle, or at least a fuel cell powered plug-in motor block for the winter time.

  22. jkvasan
    October 15, 2013

    @Wketel,

    Could there be an accelerated power requirement at the start as the stationary vehicle presents a greater mass impact compared to a moving one? Once it starts moving, the momentum would aid further motiion while the power needed is just to maintian the motion , isn't it?

  23. WKetel
    October 15, 2013

    Jayaraman, yes, inertia is always present, and at startup it must be overcome. BUT not with a huge current draw, but rather 2x or 3 x the rolinh currentdraw. My point being that a rational start is not a huge horsepower event, but rather a gental accelleration.

  24. jkvasan
    October 18, 2013

    @Wketel,

    I am curious to know when the power drawn is at its peak. My guess is at the start and while the vehicle is stopping suddenly. Is it right?

  25. SunitaT
    October 29, 2013

    Electric scooters are plug-in electrical vehicles with 2 or 3 wheels that could be recharged from any exterior cause of electricity, and the voltage is stored on board in a rechargeable battery, which controls one or more electric vehicles to attain locomotion. Electrical motorcycles, as well-known from scooters, do not have a step-through frame.

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