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  1. #1
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    Does Phase Currents are always RMS

    When you are driving a PMSM motor or any kind of motor, we always refer to phase currents Ia, Ib, Ic. My question is whether the currents are RMS values? or i need to derive them separately?

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  2. #2
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    Re: Does Phase Currents are always RMS

    Hi,

    Ideally it should be noted in the datasheet whether it is RMS or any other.
    But usually it is RMS.

    What do you do with this value?
    Example:
    If you calculate winding dissipation power in an AC system ... RMS is the only suitable value.

    Klaus
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  3. #3
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    Re: Does Phase Currents are always RMS

    In the microchip application note AN2520 they have shared the experimental results. If i have to do a similar exercise how do i capture the RMS current? Is it from the oscilloscope?
    Click image for larger version. 

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  4. #4
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    Re: Does Phase Currents are always RMS

    Hi,

    .. it clearly says "A RMS"

    How to get RMS value:
    * true RMS DVM (maybe you need to filter out switching frequency ... in case you see some alias frequencies artefacts)
    * scope with RMS function
    * ADC and microcontroller with RMS calaculation
    * RMS-to DC converter and DC voltmeter
    ....

    Klaus
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