Power in Flux

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Type: Posts; User: podolefsky

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    The encoder tells the controller the actual RPM...

    The encoder tells the controller the actual RPM of the rotor. Then the controller varies the field rotation frequency accordingly.

    On an induction motor, the torque is proportional to the...
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    Induction doesn't need to know position at all,...

    Induction doesn't need to know position at all, just RPM.
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    Yes! I love those efficiency maps. I wish every...

    Yes! I love those efficiency maps. I wish every manufacturer made them.

    It's also helpful to look at power vs rpm maps, that can be found here.

    Look on page 5 and imagine your cruising along...
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    Holy crap...this sounds like CONSENSUS. I...

    Holy crap...this sounds like CONSENSUS.

    I thought this day would never come...it is bittersweet.
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    Good point. That's sort of what I was getting at...

    Good point. That's sort of what I was getting at before, unless you have a UQM/Remy (or used a bicycle as the chassis), you're probably going to hit a performance wall at some point.

    So more...
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    Just the drive train and batteries. ...

    Just the drive train and batteries.



    yeah...I'm aware ;)
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    Yeah, that's kinda what I'm after...although I'd...

    Yeah, that's kinda what I'm after...although I'd extend it a bit to ask about any motor/controller/battery combo that we can actually buy and is within a reasonable budget.

    The goal: a bike with a...
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    A little research - turns out, the Curtis max RPM...

    A little research - turns out, the Curtis max RPM setting is 8000. I'm guessing that's about the physical limit of the motor as well.

    If I want my same top speed of around 90 mph, with 8000 RPM I...
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    ...and we come full circle, yet again... I had...

    ...and we come full circle, yet again...

    I had actually worked this out a while ago (when I was still contemplating the AC conversion). The Curtis maxes out at 130V, which means I could run 36s...
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    No problem...the controller, on the other hand,...

    No problem...the controller, on the other hand, is $15,000... :rolleyes:

    Sent from my PC36100 using Tapatalk 2
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    So basically, if I could run my AC20 at 144V...

    So basically, if I could run my AC20 at 144V instead of 72, and it could spin at 12000 RPM without flying apart, and I had 30Ah cells that could do 20C...I could gear down by 2x, double the wheel...
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    But according to the spec, you need 450V to hit...

    But according to the spec, you need 450V to hit 16000 rpm...and 550A for that torque. So basically a pack with 6x the power of mine. Even with lipo, that's going to be more than 30lb (I think).
    ...
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    True, the AC-20 isn't the lightest or most...

    True, the AC-20 isn't the lightest or most efficient motor. But that's what I was saying, that no matter what you start with, you're always going to be able to ask the question "could I double the...
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    Here's a question: Suppose I have an AC-20,...

    Here's a question:

    Suppose I have an AC-20, 650A controller (which I do). Even at 72V, I can gear this to go 90+ mph and have acceleration that makes me smile. At 96V, I'd be rockin even harder.
    ...
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    Agreed...and I'll just add, in my opinion, the...

    Agreed...and I'll just add, in my opinion, the elegant simplicity of direct drive.
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    I see your point. Just clarifying that motors...

    I see your point. Just clarifying that motors have both speed and torque constants...you're right about the *ability* of the motor, given that the rest of the system is matched.




    That's what...
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    Yup. Another way to look at it is conservation of...

    Yup. Another way to look at it is conservation of energy. If you go from 0-60 mph, you have put the same amount of energy into the bike whether you did it in 5 seconds or 5 minutes, and whether you...
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    That's the best reasoning I've heard so far...

    That's the best reasoning I've heard so far...
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    Most motors use Class H insulation, rated to 350...

    Most motors use Class H insulation, rated to 350 F. If you can touch it without getting burned, it's fine.
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    OK then, replace the tranny with a larger motor,...

    OK then, replace the tranny with a larger motor, controller, and batteries. :D

    Chip Yates had no need for a transmission - at some point, some company will finally make a motor about half the size...
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    Right. Here's *another* chart that I've used to...

    Right. Here's *another* chart that I've used to try and explain battery vs motor amps.

    (Apologies to folks who are getting tired of my charts and graphs...I think once you understand them, it...
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    This was discussed somewhat in another thread...

    This was discussed somewhat in another thread (which I can't find now). What you need are efficiency maps, and very few manufacturers provide them (I know UQM does). I think we figure out that you...
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    So anyway...transmissions...

    So anyway...transmissions...
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    Wow - how did we get on engine braking? Back...

    Wow - how did we get on engine braking?

    Back to Ted's original point...I noted that the graphs I posted weren't exactly apples-to-apples. But, it does highlight the point about having a "balanced...
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    All due respect, have you built and/or ridden an...

    All due respect, have you built and/or ridden an electric bike? I didn't start messing with all these charts and data until I had ridden with different ratios and felt the difference. The butt dyno...
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