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  • Ramani Aswath
    Ramani Aswath

    @ramani-VR4O43 • Feb 1, 2016

    VA rating is three times average current (~40 amps) x average voltage (~420) between two phases. Divide by power factor.
    Approx.: 16800x3/(PF) VA

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 2, 2016

    power factor value??
    i have 0.999 pf in my main meter.
    so can i take 0.999 as a power factor?

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  • Ramani Aswath
    Ramani Aswath

    @ramani-VR4O43 • Feb 2, 2016

    You cannot. The motor can and probably will have a lower pf. Please check the original label.

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 2, 2016

    in my plant one motor is running on star delta starter it takes 80 amp average then i have provide drive in that motor, then it takes at 45 hz 75 amp(output of drive) and 62 amp(input of drive), so please tell me which ampere is require to take for unit calculation?
    input or output amp?

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  • lal
    lal

    @lal-R60Xjx • Feb 2, 2016

    Input it would be. Motor and drive together should be considered. Drive would be dissipating a part of the energy it consumes as heat (losses) and transfer the rest to motor.

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 3, 2016

    then why input and output ampere has different? input amp is very low why?

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  • lal
    lal

    @lal-R60Xjx • Feb 3, 2016

    When you calculate the power at input and output, you'll see the output is lesser than the input due to losses.

    Anyway, to answer the question, the motor driver is able to alter the voltage and frequency of power output to control the mechanical characteristics of motor - torque and speed. So the voltage and frequency of input power will be different from the same at output of drive.

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 3, 2016

    but sir.
    i have also put a energy meter in that panel.
    in energy meter it show output ampere instead of input.
    why this happen.?

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  • lal
    lal

    @lal-R60Xjx • Feb 4, 2016

    Wait, it looks like I have perceived 'drive' the wrong way. Is drive simply a star-delta starter or a power electronic motor controller? And I assume we are talking about an induction motor.

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 4, 2016

    drive means inveter. frequency variable controller for motor.

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  • lal
    lal

    @lal-R60Xjx • Feb 5, 2016

    Did you say the input current of drive from its spec? If so, it would not be more than the mentioned value unless overloaded!

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 6, 2016

    now i have provided inverter in 15kw motor
    inverter input current is15 and output current is 19 amp.
    now tell me how many power consumption of this motor?

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  • lal
    lal

    @lal-R60Xjx • Feb 6, 2016

    Around 7kW if voltage is assumed to be 415V, 3phase, power factor to be 0.8 lagging and inverter efficiency around 80℅.

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 17, 2016

    how??
    please send formula for calculation........

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  • lal
    lal

    @lal-R60Xjx • Feb 18, 2016

    Directly calculating motor power using the formula to deduce power cannot be used as converter output will be having a different voltage than the input. So the total input power to converter can be calculated and approximated to motor power assuming an 80% efficiency for conversion.

    Total input power to converter = 3^(1/2) x 415 x 15 x 0.8 (assuming 0.8 lagging p.f.)
    Total power = 8626W
    Assume 20% of total power is used by converter electricals and dissipated.
    Total motor power = 8626 x 80% = 6900VA
    Actual value may be more than that. So motor power can be assumed to be around 7kW.

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  • vijayppatel13
    vijayppatel13

    @vijayppatel13-Rzav3Y • Feb 18, 2016

    you have assume 0.8 lagging power factor..
    but in my main meter i have 0.999 power factor.
    so can i take 0.999 pf??

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  • pankaj.bhatt376
    pankaj.bhatt376

    @pankajbhatt376-IQc8vy • Feb 19, 2016

    Yes you can assume 0.999 power factor

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