hall sensors for acquire currents

Discussion in 'The Projects Forum' started by alioshak, Nov 4, 2013.

  1. alioshak

    Thread Starter Member

    Jul 31, 2009
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    Hi,
    I am using a hall sensor to acquire currents of a 3phase induction motor, the max current of the sensor (Imax) is 7A, but when I the motor starts working it present a 15A current during 1 second. As I am working with parameters estimation I need the transitory currents, in this sense I have a dude: observing the signals it seems to be that the currents are cutted as if it has a saturator, I would like to know if this "saturation" is due to the measurement overpass the sensor specifications (Imax.7A) or if it is the normal behavior of the currents when the motor start working.

    I am attaching a figure of the currents.

    Thank you very much for your help :)
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,779
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    Can you make/fix a current shunt such that the sensor only sees a known fraction (e.g. 30%) of the motor current?
     
  3. alioshak

    Thread Starter Member

    Jul 31, 2009
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    thank you Alec_t, it is a great idea!!, I will try and post the results!
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    2,369
    Any particular reason you didn't use a current transformer?
    Very easy to tailor a ratio.
    Max.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    On power on, a 3 phase motor represents a transformer with a shorted turn secondary, the current will naturally be Very high, this will only decrease as the motor rotor starts to rotate, time taken will depend on load etc.
    Max.
     
  6. alioshak

    Thread Starter Member

    Jul 31, 2009
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    thank you for your MaxHeadRoom,
    that is correct, the current should be high, but I would like to know if the currents I obtained (they could be observed in the pic attached) during the transient (aprox. 15A) are the real ones or if they are distorted ("cutted") due to the sensor specifications (Imax 7A). Today I don't have access to the lab, tomorrow I will.
     
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    What hall sensor model are you using? The datasheet will tell you if it saturates.
     
  8. alioshak

    Thread Starter Member

    Jul 31, 2009
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    Hi, praondevou, thank you for your answer
    I am using a CSNE151 it has several primary pins configurations according to the current you want to measure, but mine is configured for an Imax of 7A, I am not able to change this configuration, it is fixed. I looked for the information in the datasheet but I did not find it, may be I do not have enough knowledge :(
     
  9. alioshak

    Thread Starter Member

    Jul 31, 2009
    10
    0
    Hi everybody!
    Just to close the issue. The datasheet of the hall sensor CSNE151 does not have information about the saturation, however I did some experiences and notice that if you over pass the Imax values specified, the values of the current will be saturated, no mater if the overpass value is just some seconds.
    Thank you very much for your help!
     
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