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Thread: eAssist AC Induction Motor

              
   
   
  1. #21
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    Kyle, thanks for sharing the great idea. I was looking for a good watercooled ACIM to test the control algorithm for my thesis project. This one looks pretty promising.

    Used motors are available from auto wreckers. I searched http://car-part.com/ and found one from a 2012 Buick Lacrosse 2.4L eAssist for $155 shipped. There was no core required or core charge. It also comes with a lifetime warranty from the wrecker. As soon as I receive it, I will weigh it and I will hopefully fully test it once my controller is finished.

  2. #22
    Empulse R #24 frodus's Avatar
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    Re: eAssist AC Induction Motor

    Thanks dude! Looks like they have a few!

  3. #23
    Moderator Nuts & Volts's Avatar
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    Great find yeaw!...decisions...decisions. I'm never going to actually pick an AC system now haha
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  4. #24
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    Keep in mind, "field weakening" is just a legacy term from sep-ex days, and in the case of a PM motor it's nothing more than timing advance (so you switch the voltage to the coil a few degrees before the magnet passes by the coil generating that BEMF that would have made it impossible to continue feeding current into that coil (because BEMF and packV would be equal), so you can continue to rev at the cost of efficiency and torque. In an induction motor, it simply means increasing the slip rate target, which basically does the same thing. It's not like it has a magic trick to make it rev way higher for a given voltage, it's more like a efficiency/heat/torque costing neat trick to get some extra rev range. It's very cool and has it's place in a motor/controller combo for sure, but I just want to make sure you're aware that it's not like it's just free candy or something.

    On ES, a guy named Burtie made a little stand-alone box that takes the hall sensor encoder signal, and applies as much timing advance as RPMs climb as you wish to have. It's like $25 IIRC, and it gives any motor controller "field weakening", it's even programmable to set the curve up how you like. He has sold a few dozen to happy customers for ebikes that get another 10-15mph top-speed at the cost of efficiency/heat/torque, but it ONLY costs them the efficiency/heat/torque while they are operating the motor in the speed range they wouldn't have been able to achieve otherwise. To make a stand-alone box to add "field weakening" to any induction motor/controller would be even more simple, as the encoder is generally simply a rate encoder rather than position encoder.
    Last edited by liveforphysics; 04 January 2013 at 1527.

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  6. #25
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    Re: eAssist AC Induction Motor

    Ah, thanks for explaining the history. I had never heard the term "field weakening" before getting into elmotos. With industrial AC motors, I always thought; of it as just running above synchronous (60 Hz) speed.

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  7. #26
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    Quote Originally Posted by CliC View Post
    Ah, thanks for explaining the history. I had never heard the term "field weakening" before getting into elmotos. With industrial AC motors, I always thought; of it as just running above synchronous (60 Hz) speed.
    You mean base frequency (or base speed). If an induction motor runs faster than synchronous speed, it is a generator. But you are correct. When you use a VFD and drive a standard industrial motor above its 60 Hz speed, that is field weakening. And does not need an encoder for most industrial applications.
    Last edited by lugnut; 05 January 2013 at 0908.

  8. #27
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    Re: eAssist AC Induction Motor

    [QUOTE=lugnut;34722]You mean base frequency (or base speed). If an induction motor runs faster than synchronous speed, it is a generator. But you are correct. When you use a VFD and drive a standard industrial motor above its 60 Hz speed, that is field weakening. And does not need an encoder for most industrial applications.[quote]

    Yeah, it's not a generator when you are driving it at over 100% of its across-the-line speed with a VFD (though we rarely do that). But yes, "synchronous" is a somewhat sloppy term for induction motors because of slip. Maybe I should've said "1750 rpm"

  9. #28
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    In looking at the video the speed sensor looks to me a lot like a Tamagawa resolver. It's hard to tell from the picture how many poles it is, but I doubt it is 10. If the motor is 8 poles then you wouldn't want to have a 10 pole resolver. I find it a bit odd that they would use a resolver on an induction motor. I wonder if they have planned to have a different rotor that had magnets???

    Does the Sevcon unit actually support a resolver (provides excitiation to resolver) or does it support a sin/cos encoder? I have heard that on some models they don't support a true resolver. Since the Curtis doesn't support a resolver you would have to add your own speed sensor.

    The motor looks pretty cool. It would be interesting to put it on the dyno and see what it can do with ~ 320V.

  10. #29
    Senior Member Athlon's Avatar
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    AFIK sevcon have input for 3 hall sensor , sin/cos encoder and a quadrature encoder (A B signal square wave) ,

    Curtis only support quadrature encoder as they only support induction motor

  11. #30
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    Re: eAssist AC Induction Motor

    I still have not gotten a response from any of the parts dealers about the motor.....

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