Magnetic field near a condcutor 300 A DC

[peranders]

How many Tesla is healthy for my Traco TME DC-DC converters? My concern is if the DC-DC converter may get saturated transformer cores.

My application is two 300 A, DC 10 x 20 mm copper bars 60 mm apart (50 mm space). Between the copper bars I’m going to place a H-bridge driver including three 12 V DC-Dc converters.

A forumla says 0.3 Tesla 1 cm from the conductor. This seems much. Anybody who have a theorectical insight in this?

The current flows is different directions.

[AndrewT]

Hi,
if the current flows in opposite directions then the far field effect is near zero.
Close up or between the conductors will have a much bigger effect.

Keep the TV and compass at bay.

[peranders]

Andrew, my question is what happens bewteen the copper bars.

[jneutron]

Originally posted by peranders
How many Tesla is healthy for my Traco TME DC-DC converters? My concern is if the DC-DC converter may get saturated transformer cores.

Hopefully, traco will specify the sensitivity of their supply design to external DC magnetic fields. There will be minimum as well as maximum orientation sensitivity, depending on the design of their ferrites.

There will also be a temperature component to that sensitivity as well, higher temps of course being worse for magnetic sensitivity.

As posed, that specific question is not answerable by anybody other than the manufacturer.

Originally posted by peranders

My application is two 300 A, DC 10 x 20 mm copper bars 60 mm apart (50 mm space). Between the copper bars I’m going to place a H-bridge driver including three 12 V DC-Dc converters.

A forumla says 0.3 Tesla 1 cm from the conductor. This seems much. Anybody who have a theorectical insight in this?

The current flows is different directions.

Go here:

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Under Biot-Savart, there is a calculator for a single loop magnetic field.

Just looked at what the link gives..

Click on ele and magnetism...then biot-savart, scroll down to the pic of the single loop, click on it.


Cheers, John

[peranders]

I have just tested with 2000 A and the inpact was minor, I'd say. Less than 100 mV on a 5V to 5V converter. It may be nothing to worry about.

[Elvee]

Anyway, at a distance of 1cm you only get 0.006T (for one conductor, in the air).
There will also be a contribution of the other conductor, but it will be lower: 1/5th.
LV

[peranders]

Can you tell me the formula? I've got 0.3 T which seemed way out wrong.

[PigletsDad]

For a long straight, filamentary conductor

B = mu0 2i / 4 pi R

where mu0 = 4 pi x 10^-7, i is the current in amps and R is the radius in meters.

cancelling the 4pi gives

B = 2 x 10^-7 i /R

For R = 1cm and i = 300A, this is 6x10^-3 T

For an extended conductor, you should really integrate over the cross section, but usually just measuring the radius from the centre is close enough, which reduces B a bit more.

I would be amazed if 6mT had much effect on the ferrites.

[jneutron]

Originally posted by PigletsDad
For a long straight, filamentary conductor

B = mu0 2i / 4 pi R

where mu0 = 4 pi x 10^-7, i is the current in amps and R is the radius in meters.

cancelling the 4pi gives

B = 2 x 10^-7 i /R

For R = 1cm and i = 300A, this is 6x10^-3 T

For an extended conductor, you should really integrate over the cross section, but usually just measuring the radius from the centre is close enough, which reduces B a bit more.

I would be amazed if 6mT had much effect on the ferrites.

As you stated correctly, the formula is for a long straight conductor.

Outside of the actual conductor, assuming circular cross section, the field will be independent of the size of the conductor. If the conductor is not cylindrical, that will not be correct.

For the problem at hand, if the supply is between the two conductors, field will enhance, it will be necessary to double the strength calculation...a whopping 12 mT..

If the 300 amps forms a loop, it can be as much as pi times 6 mT. It was the loop case I linked to.

Sheesh, at those field strengths, shouldn't there be some kind of safety barrier???

Cheers, John

ps...it's great to see others using Max's stuff..

[jcx]

I wouldn't dismiss a free air 12 mT - it represents enoungh H to saturate some ferrite materials, μ_r of 500 gives B of 0.6T

a Iron (low carbon steel) box would divert the flux, shielding the smps magnetics