3 phase shunt current sampling sampling

[Amin Khorsandi]

hello everybody
I used shunt for current sampling and I had no problem by shunt but in a project I found a problem. sampling 3 phase current using 3 shunts, if there is no isolation (for example not using CT before shunts) could cause current interference and sampling didn't work well.
could someone please give me a point to build a circuit for 3 phase (not isolated) sampling using shunt?

 

[cl10greg]

If you are using magnetic sensors, you would need to separate them by a sufficient distance to prevent cross talk of the sensors. Depending on the routing, you could do twisted pairs to try and minimize the noise as well.

 

[schmitt trigger]

Amin: first things first:
is your load delta or wye connected?

 

[Amin Khorsandi]

Amin: first things first:
is your load delta or wye connected?

I want to yous bothe of them. The measurement device must support all type of loads.
Due to low space I have no choice but using shunts.

 

[schmitt trigger]

Non-isolated current sensing, on a delta load?
Those are conflicting requirements, you can't do it.

Only if the load is fully balanced, you could get away with measuring only two phases in a delta connection, and calculate the third.

Now:
If you don't have space for CTs, can you use a hall cell solution? What is your current range?
There are some hall cell current sensors, good for 30 amps, available in a SOIC-8 package, which is no larger than what a shunt resistor would be. And fully isolated for 2 kV RMS.

Check the ACS712 datasheet.

 

[Amin Khorsandi]

current range is 0-5 ampere. so I have to choose acs712 I guess. thanks for your attention

 

[schmitt trigger]

The ACS712 also comes in a 5 amp version

 

[Amin Khorsandi]

The ACS712 also comes in a 5 amp version

yes it is. but it's a little expensive for my project. if I could use shunts instead I would be more glad.

 

[schmitt trigger]

Non-isolated current sensing, and a delta load are mutually exclusive requirements. But they can be solved.

If you add small size and low cost, I'm afraid that there will be no solution to your problem.