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Thread: Most efficient theoretical voltage and frequency for Induction motor.

  1. #1 Most efficient theoretical voltage and frequency for Induction motor. 
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    I'm part of a new electric vehicle manufacturer and though I've got some experience building EVs, I'm lacking much education that would help me understand why people use the motors, voltages and frequencies that they use. Setting aside the safety issue of electricity being able to more easily move through air and skin to cause damage to us, why don't we build EV motors that use 1000 volts? Even for trains, the most I've heard of (I'm no train expert either) is somewhere around 700 volts. I am also hoping to disregard batteries and motor controllers (in terms of availability) in the discussion and stick to motor efficiency. My electric motorcycle only runs at 120 volts and a huge portion of the total available power gets lost in the motor. What I'd like to do is come up with a motor that doesn't get hot.
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  2. #2  
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    Quote Originally Posted by owlexmyth View Post
    ....Setting aside the safety issue of electricity being able to more easily move through air and skin to cause damage to us, why don't we build EV motors that use 1000 volts? ....in the discussion and stick to motor efficiency. My electric motorcycle only runs at 120 volts and a huge portion of the total available power gets lost in the motor. What I'd like to do is come up with a motor that doesn't get hot.
    The dielectrical breakdown of thin insulating materials used in windings will limit voltages. You answered this yourself with the dielectric breakdown of air.
    Small electric motors are 80% efficient. Large ones 90%. This is much more efficicient than IC engines, much better torque characteristics also
    Electric motors run hot because the use of superior materials allows this, thus reducing cost, size and power consumption. They still run cooler than IC engines. One of the reasons ceramics are researched for motors and engines is to allow them to run hotter.
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  3. #3  
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    I have never looked into this, but I think most electric motors generate mechanical force because of the current flowing through coils of wires which create magnetic fields. When current flows through wires, there is resistance to the current flow which creates heat. I should think that the heat could also be used to create some sort of a desired use - In a gas engine it can at least be used to heat the interior when it is cold out, but much of the heat is just really wasted. Resistance dissapates usable power I think, and turns it into heat , but since heat is also an energy, could it not be used to create some sort af auxiliary steam force to also help to generate more mechanical energy?

    @ Owlexmyth, are you sure your electric motorcycle operates at 120 volts, and that the 120 volts is not just simply what is used to charge its batteries?
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  4. #4  
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    Quote Originally Posted by mayflow View Post
    Resistance dissapates usable power I think, and turns it into heat , but since heat is also an energy, could it not be used to create some sort af auxiliary steam force to also help to generate more mechanical energy?
    You need to study some science. In this case, thermodynamics is what you need to focus on. Google for it. Other terms of relevance would be "Carnot cycle" and "heat engine efficiency limits" etc.

    The bottom line: Not all energy can be turned into work.
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