hall sensors for acquire currents

Thread Starter

alioshak

Joined Jul 31, 2009
10
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 :)
 

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Alec_t

Joined Sep 17, 2013
14,280
Can you make/fix a current shunt such that the sensor only sees a known fraction (e.g. 30%) of the motor current?
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
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.
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.
 

Thread Starter

alioshak

Joined Jul 31, 2009
10
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.
 

praondevou

Joined Jul 9, 2011
2,942
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).
What hall sensor model are you using? The datasheet will tell you if it saturates.
 

Thread Starter

alioshak

Joined Jul 31, 2009
10
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 :(
 

Thread Starter

alioshak

Joined Jul 31, 2009
10
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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