more inductor lies

[John Larkin]

This looks too good to be true.

https://www.digikey.com/products/en?keywords=deno-25-0001

It saturates at about 60 mA.

 

[Arie de Muynck]

On 2019-09-11 20:23, John Larkin wrote:

This looks too good to be true.

https://www.digikey.com/products/en?keywords=deno-25-0001

It saturates at about 60 mA.

A ground wire choke, the wire is thick to withstand 16A currents without
interrupting the PE path. The extremely high inductance with so few
turns give the high ur away, and that will saturate easily.

I was once bitten by this effect - during the EMC test it looked fine
and we passed, but when real ground currents occurred the suppression
was gone and we got too much noise. Had to put in a bigger choke, and
retest and re-qualify. With some discussion and documentation we could
fortunately avoid most of the re-qualification costs.

Arie de Muijnck

 

[John S]

On 9/11/2019 1:23 PM, John Larkin wrote:

This looks too good to be true.

https://www.digikey.com/products/en?keywords=deno-25-0001

It saturates at about 60 mA.

Yeah, and all three models have the same SRF? Don't worry... they're not
available anyway.

 

[legg]

On Wed, 11 Sep 2019 11:23:36 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

This looks too good to be true.

https://www.digikey.com/products/en?keywords=deno-25-0001

It saturates at about 60 mA.

Ground current limits, through common-mode and stray capacitances, are
typically restricted to being 30 times smaller than this, at the power
line frequency and it's lower multiples.

RL

 

[legg]

On Wed, 11 Sep 2019 21:28:58 +0200, Arie de Muynck
<no.spam@no.spam.org> wrote:

On 2019-09-11 20:23, John Larkin wrote:

This looks too good to be true.

https://www.digikey.com/products/en?keywords=deno-25-0001

It saturates at about 60 mA.

A ground wire choke, the wire is thick to withstand 16A currents without
interrupting the PE path. The extremely high inductance with so few
turns give the high ur away, and that will saturate easily.

I was once bitten by this effect - during the EMC test it looked fine
and we passed, but when real ground currents occurred the suppression
was gone and we got too much noise. Had to put in a bigger choke, and
retest and re-qualify. With some discussion and documentation we could
fortunately avoid most of the re-qualification costs.

Arie de Muijnck

Where was this choke located, w/r to any protective earth and what was
the power rating of the component, or system?

RL

 

[Phil Allison]

John Larkin taking the piss again wrote:

----------------------------------------

This looks too good to be true.

https://www.digikey.com/products/en?keywords=deno-25-0001

It saturates at about 60 mA.

** The stated app is one where little current flows in the choke.

The 16A (or 20A) rating allows for fault conditions and large surges while keeping series R low enough to pass PAT testing.


..... Phil

 

[Arie de Muynck]

On 2019-09-12 03:03, legg wrote:
Where was this choke located, w/r to any protective earth and what was
> the power rating of the component, or system?

Data acquisition system in a factory, 16A choke in the PE of the mains
connection to minimize RF noise entry from the mains. Unfortunately the
customer used some I/O single ended and grounded the other end for
safety (original spec said I/O was floating). The ground loop currents
came from voltage drop over the mains installation PE wiring (heavy
motors in the vicinity). The choke saturated and passed too much RF
noise for the high sensitivity (differential) thermocouple input circuits.

Power rating? I guess that was about 50VA for the DAQ system. Mains
fusing for our outlet was 16A, hence the choke rating.

Arie