What is the effect of 30A Line Crurrent close to PCB circuit

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What is the effect of 30A Line Current close to PCB circuit

Hi All,
I'm designing a three phase power meter based on a ADE7758 and want to use PCB based Current Transformers (CT's) of 30A/30mA. This means there will be 3x30A caring line wires running cm-ers over the PCB trough the CT's. Its similar like the meter below but now with three phases. I'm worried about the induced noise on the PCB wiring by this 50/60 Hz magnetic field coming from the line wires. Is there any one who has experience on the sensitivity of using changing 50/60 Hz magnetic fields close to PCB traces. Does any one have suggestion show to shield this if needed .
Thanks so far

Regards Oscar
 
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Magnetic field per se is not the problem; the induced voltage on the conductors is. However, 30A at 50-60Hz can be noisy and it is best to mount the CTs on a different board and shield them with a thin iron sheet.

The magnetic field produced by a simple current carrying conductor is in concentric circles centered around the conductor. All long traces that are sensitive to the induced voltage should be arranged parallel to the conductor.

The three conductors should be kept parallel and the connection to the CTs should be by twisted wires to the main board. As the return current is also carried by the same wires, the problem should not be severe.

However, I do not have personal experience about these devices.
 
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    wogoos

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Hi,

The magnetic field produced by a simple current carrying conductor is in concentric circles centered around the conductor. All long traces that are sensitive to the induced voltage should be arranged parallel to the conductor.
Click to expand...
The magnetic filed is running in circles, true. But voltage/ current will be induced in traces that are in parallel with the 30A wire. If you want to avoid induction ...sensitive traces should be 90° to the 30A wires.

Short traces in differential signaling are good design techniques. Only analog signals are probkematic, because the influence in digital signal should not be big enough to change the logic level.

Klaus
 
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    wogoos

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KlausST said:
The magnetic filed is running in circles, true. But voltage/ current will be induced in traces that are in parallel with the 30A wire. If you want to avoid induction ...sensitive traces should be 90° to the 30A wires.
Click to expand...

Sorry for the goof-up and thanks for correcting!!
 
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