Need small ferrite button

[Yzordderex]

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

regards,
Bob

 

[Anders F]

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

Sorry - but if you can handle the cost, Allegro has readily available
integrated 50/100A current probes...

/A

 

[Rich Grise]

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

I've done a quick search, and so far just come up with ferrite
rod cores, which you _could_ slice with a diamond saw. Call some
ferrite dealers, maybe.

Good Luck!
Rich

 

[Tim Wescott]

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

regards,
Bob

No, but here's three things to think about:

1. Use a plain-ol ferrite bead. IIRC the Fair-Rite FT-101 size is 1/8
by 1/8. It'll stick up from the board to an alarming degree, but
perhaps it'll work in your application anyway?

2. I've been wondering for quite a while now if you can laser cut
ferrite -- it's a ceramic so it may not cut well at all, but you never
know. If it's possible, consider getting ferrite sheets and having your
buttons cut from that.

3. Does it have to be ferrite? If your frequencies are low you could
use an iron (and I mean _iron_, not steel) or nickel button. This may
be much easier to obtain (and I _know_ you can laser cut the stuff!).
One of the higher-permeability iron powder mixes may also work, and you
can cut that stuff with a hacksaw and file if you want.

 

[legg]

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

Miniature bobbin cores used in RF IF transformers are often two-part
assemblies with a disc end that glues on.

Power bobbins bobbins don't usually seem to go below 12mm, but Tokin
does one at 6.6mm dia in mpp or iron dust.

You can also buy ferrite polymer sheets that can be detail-punched
into whatever size of part you want. These are offered by Siemens,
TDK, MMG, Tokin, Hitachi and TSC.

If it was just for low frequencies, I'd use soft iron.

RL

 

[Ken Smith]

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

Philips.


Does it really have to be a disk?

Coil craft makes inductors that are two disks with a very short rod core
between them. The whole thing is less than 1/8" thick and surface mounts.
You could try one of them.

 

[Keith Wootten]

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Not a disc, but how about a surface-mount ferrite inductor? Don't
connect the coil but use it as a lump of ferrite. Farnell has loads,
for example 305-6510 is 0805 size.

Cheers