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Thread: Simple Integration - Newbie without a clue

  1. #1
    Feb 2010

    Simple Integration - Newbie without a clue


    Its been years since the grey matter was used for this type of math. Its true what they say if you don't use it you lose it. I can say that I cannot remember how to integrate.

    So onto the problem, its a simple Time/Speed/Distance problem.

    I have an A.C. motor that I need to accelerate to a certain rpm with a certain torque. Here is some figures

    Torque = Nominal torque * ( Base speed / Max Speed )
    Max Torque = Max torque * ( Base speed / Max Speed )

    Nominal Torque = 175kNm
    Max Torque = 438kNm ( for 15 seconds )

    Nominal Torque @ Max Speed = 63kNm
    Max Torque @ Max Speed = 156kNm

    So in essence as the rpm increases the available torque decreases.

    I now have a load to put on the motor.

    If I have a torque of 260kNm ( This equates to a acceleration rate of 2.5m/s2) and I want to get to an rpm of 700rpm

    At 700 rpm I only have available 75kNm nominal and 188kNm maximum

    So I don’t have enough power to accelerate at 2.5m/s2

    The break point is at 505rpm.

    From 0 – 505 rpm I can accelerate at a constant 2.5m/s2 because I have the max torque available
    From 505 – 700 rpm for every increase in rpm I get a decrease in available torque.

    Therefore from 505 – 700 the accelerate rate will reduce as the rpm increases.

    What I need to calculate is the time it takes to accelerate from 0 – 700 rpm, Also the distance travelled to do this acceleration.

    So I hope this made sense to someone, I am hoping someone can help me with a solution My goal is to put this into excel so I can automatically calculate these figures for different input data.

    One other problem I can see, is for example if the example above 10 seconds and 7 meters to get to the required rpm. What if I were only 'allowed' 6 meters I would have to calculate what speed I could achieve and how long would it take.

    I understand I'm probably asking a lot so if anyone could help that would be amazing. Even if you cannot solve it all put give me a few pointers that would also be fantastic.

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  2. #2
    Feb 2010
    can anyone help ?
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