Cracked Inductor Core?

[Shaun]

The inductance may still be correct but the core may saturate early if cracked.

I believe the inductance (even better: the inductance curve) should indicate if there has been an effect in the magnetic circuit. A gap introduced should actually raise the saturation point, unless the damage has resulted in a part of the core getting excluded from the magnetic circuit. But in that case the inductance should change (the introduction of a significantly-sized gap should have the same effect).

 

[AllenB]

presumably the "ferrous powder" has insulated particles to reduce Eddy current loss - again the barely visible cracks wouldn't change loss behavior

If this is indeed an insulated particle material, then +1 to this..aside from..

if the broken pieces manage to vibrate slightly as the flux swings through, and the attraction force can get quite high between pieces, it's going to cause distortion. How much distortion I couldn't say <snip>

 

[Spuddy]

After sleeping on it, a couple of the cores look deeply cracked enough that there is potential for cores to have been damaged. I wasn't able to test this, but nonetheless, they are at least a bit unsettling to think about, and as such I've sent an email to Europe Audio asking what we should do from here

Thanks for all of the input, I've learned a lot about these components from this thread, so even if I need to wait a while, there's still something positive to think about

 

[Spuddy]

3 days since contacting europe-audio.com asking what we should do to rectify this little issue, and still no response whatsoever.. Looks like I'm getting blown off again. After my order taking 3 weeks longer than advertised to even leave the factory (with no communication whatsoever from them letting me know why I was left waiting), I can't say this is a surprise.

Since I paid with PayPal, I could likely file a complaint and get some good parts eventually, but frankly I'm tired of waiting on a sketchy company that doesn't communicate, and even if I send these things back, I can't honestly say I'm confident that good parts would be sent back in replacement.


sooooo..

I believe the inductance (even better: the inductance curve) should indicate if there has been an effect in the magnetic circuit. A gap introduced should actually raise the saturation point, unless the damage has resulted in a part of the core getting excluded from the magnetic circuit. But in that case the inductance should change (the introduction of a significantly-sized gap should have the same effect).

If this is indeed an insulated particle material, then +1 to this..aside from..

The general vibe I get from this is that the inductors are likely going to be just fine assuming I stabilize them, and at this point, stabilizing and using them is what I'm most comfortable doing. Even if they can't do the job right, it's only a $60-$70 total fix (from a different supplier of course), and to me it's worth that to not left in the dog house for another month waiting.

I have several 5 minute epoxies, as well as some super glue. Would I be best off filling the cracks with super glue as metioned earlier in this thread, or would it be safer to fill a 1/4" deep circular cutout with epoxy and mount the coils cracked-end down, to both stabilized and mount the coils at the same time?

 

[Shaun]

Super glue will allow minimal gap, and is quicker.

 

[lykkedk]

Hey sorry to see, that you have to struggle this...

I suppose that, the inductors is from : Jantzen ? Jantzen Audio Denmark - Contact

So, if Europe-audio does not reply during X-mas, maybe you can contact the Jantzen Denmark ? -
Normally, a shop like that, will return, (let you keep the bad parts) new parts. - Only from the look of the pictures...

Just a thought ??? - And marry Xmas btw...

Jesper

 

[Mooly]

Well if you are going to glue them up then maybe heat them to say 50 or 60C and use epoxy. Perhaps a normal "slow one" like Araldite original as that will hopefully get drawn into the gaps as it cools and at warn temperatures it still sets fairly quickly.

I see Shaun recommends superglue... dunno on that one... I always used epoxies (and Yacht varnishes ) for sealing noisy ferrites and so on in SMPS work. Super glue while excellent for many things is brittle and can leach salts (that white deposit) as it cures.

 

[jcx]

I believe the inductance (even better: the inductance curve) should indicate if there has been an effect in the magnetic circuit. A gap introduced should actually raise the saturation point, unless the damage has resulted in a part of the core getting excluded from the magnetic circuit. But in that case the inductance should change (the introduction of a significantly-sized gap should have the same effect).

I think you (and others in this thread) are not thinking correctly about how a bobbin core actually works

there is already a long air gap path, basically the hieght of the winding

the barely visible cracks must be order of ~ 1:1000 fraction of the air path between the ends of the core, outside of the coil

 

[Starre]

My experience is that you have to call Europe audio, they are very bad with answering e-mails but better if you call them. Good luck .

 

[Shaun]

I think you (and others in this thread) are not thinking correctly about how a bobbin core actually works

there is already a long air gap path, basically the hieght of the winding

the barely visible cracks must be order of ~ 1:1000 fraction of the air path between the ends of the core, outside of the coil

There is not sufficient information available to make any assertions about the shape of the core (unless, of course, you are familiar with these products). In that context, I don't see a problem with what I wrote.

Also, I believe that you are mistaken about the effect of a through-hole "air gap"* vs one which interrupts the intended magnetic circuit.

*I would not actually call it a gap because, if it looks like a cotton reel, then the magnetic material is continuous from top to bottom. Any air space in the middle that is not the screw hole is just a way to control the amount of core material to meet a specific spec.

 

[T101]

See the irony, we from Europe wait for Erse Super Q to arrive as it has a laminated steel core and a more massive one too and we deal with customs and etc just for that, and you from USA wait even longer for a Jentzen with solid cored inductors that are damaged

Transformer - Wikipedia, the free encyclopedia

Electrical steel - Wikipedia, the free encyclopedia

I would suggest, that you send them a link to that thread. You might be a $70 customer, but they are letting you down during the holidays, when you are supposed to enjoy the constructing of you crossovers and not having to deal with a deaf company that sends damaged parts.

You definitely should ask for replacement!

 

[jcx]

There is not sufficient information available to make any assertions about the shape of the core (unless, of course, you are familiar with these products). In that context, I don't see a problem with what I wrote.

Also, I believe that you are mistaken about the effect of a through-hole "air gap"* vs one which interrupts the intended magnetic circuit.

*I would not actually call it a gap because, if it looks like a cotton reel, then the magnetic material is continuous from top to bottom. Any air space in the middle that is not the screw hole is just a way to control the amount of core material to meet a specific spec.

the pic in the 1st post is pretty conclusive about the type of core geometry

you apparently don't have a clue about how drum/bobbin mag core inductors work

ever see the field plot for a solenoid?

the flux lines complete in loops threading the solenoid, and around the outside

the core perm just makes for more flux inside the solenoid compared to air coil - all of the "new" flux lines still complete in loops through the air around the outside of the wire loops making up the solenoid

I suggest you could play with Students' QuickField 5.7 to gain some EM field visualization skill

 

[Elvee]

I don't think they are really cracks (judging by the photos anyway).

If they were actually cracks, a part of the rim should have fallen off.

I have the impression the material is a lightly loaded FPC material or similar, and heterogeneities have appeared during the casting or injection process.

I would bet the material is only weakly magnetic compared to metal or ferrite.

 

[Shaun]

I agree. We're talking possibilities and probabilities here. But if there are no parts falling off (which they don't seem to be doing) I guess that means they are not damaged.

 

[Shaun]

I think you (and others in this thread) are not thinking correctly about how a bobbin core actually works

there is already a long air gap path, basically the hieght of the winding

the barely visible cracks must be order of ~ 1:1000 fraction of the air path between the ends of the core, outside of the coil

Well, hard as it is for me to admit it, jcx is right on the money here... I did not think correctly about the magnetic circuit. As long as the core is intact (no missing bits) everything should be OK.

My advice about the super glue still stands, though. Assuming those are actual cracks, with the potential for bits to fall off, I would let some super glue seep into the cracks, just in case. Alternatively, just put some sticky tape over it to prevent such an eventuality.