Team Trev

5 responses so far ↓

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  Alessandro // 2010-02-07 at 08:07 | Reply

  Just curious,
  what’s the weight of the 25 kW DC electric motor?
  Isn’ t a 3phase AC electric motor lighter, more efficient and reliable, even less costly ?
  What about the life and the number of charge/discharge cycles of the lithium battery? Do you envisage to fully discharge it ?

  Good luck
  Alessandro (Pisa, Italy)

  • 

    teamtrev // 2010-02-08 at 18:06 | Reply

    Alessandro,

    The motor we used to drive from Darwin to Adelaide was a brushed DC motor, with a mass of about 40 kg. An AC induction motor would be lighter, more efficient and perhaps even cheaper, but requires a more complicated and more expensive controller.

    A permanent magnet brushless motor is smaller, lighter and more efficient again. We have recently replaced our entire rear end with the swing-arm from a Vectrix scooter. The swing-arm, motor, reduction gear, wheel and tyre have a mass of about 27 kg. The motor is a permanent magnet brushless motor. More efficient, more reliable, but more expensive.

    Our current (120 km range) lithium ion polymer battery has an estimated life of 250000 km. The new battery will be larger, and have an even longer life.

    We have designed the car so that we do not (often) have to discharge beyond 80%.

    Peter

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  Alessandro // 2010-02-08 at 21:45 | Reply

  Thanks for your response

  Correct if I wrong,
  but as far I know an induction motor is far lighter than ANY dc motor (besides the right arguments about expensive controllers and so on)

  For example, the Tesla Roadster 3-phase, 4-poles AC motor is only ~ 30 kg but for a power of about 250 HP, much better (x 5) than the power density you envisage. Moreover, it doesn’ t need any permanent magnet and thus rare earths resources that it’s very likely they run out in the short term

  Bye, Alessandro

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  teamtrev // 2010-02-09 at 12:47 | Reply

  You might be right about the mass of an induction motor. We should be comparing continuous power per mass, and it is not always easy to find the data. I was not able to find motor mass and continuous power figures on the Tesla web site. Brusa induction motors have continuous specific power of about 0.4–0.6 kW/kg. The Raser Technologies induction motor has 0.9 kW/kg. For permanent magnet machines, the UQM machines have continuous power density of 0.75–1.1 kW/kg. But there are large variations in specific power for both types of machine.

  Tesla has an article comparing permanent magnet motors and induction motors.

  Of course, Trev could use either type of motor. The difficulty for us was to find a low-mass, efficient motor that would operate at our chosen voltage (we were operating at 150 V, for historical reasons).

  Peter

• Small, beautiful, renewable energy cars « Antinuclear // 2010-02-10 at 08:44 | Reply

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