How to glue space ferrite transformer cores? - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 20, 2017, 03:22:02 pm
content: Hi,I have a ferrite transformer base with a gap in it. It was glued when I found it.I thought about grinding dust from a scrap ferrite to create a glue.Does such a glue already exists?Thanks for your attention.JPD

author: Ian.M
author_rank: Super Contributor
timestamp: April 20, 2017, 03:31:36 pm
content: For production, you'd either mix a small percentage of size-controlled glass microspheres with the glue to space the inner and outer limbs of the core equally, or as your photo shows, have the center limb precision ground to length to automatically provide the desired gap on assembly, which has the advantage of reducing the external stray field

author: Benta
author_rank: Super Contributor
timestamp: April 20, 2017, 03:34:05 pm
content: Just use Epoxy. The middle leg gap is so large, that a thin glue film on the outside legs will make no practical influence.

author: Zero999
author_rank: Super Contributor
timestamp: April 20, 2017, 05:02:58 pm
content: Quote from: Benta on April 20, 2017, 03:34:05 pmI agree.Another thing you may want to consider is a non-magnetic spacer to glue in the middle, to improve the mechanical strength.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 20, 2017, 05:13:21 pm
content: Quote from: Benta on April 20, 2017, 03:34:05 pmThis is why I wanted to fill the middle gap with ferrite dust. Does not this gap weaken the transformer magnetic field?

author: Zero999
author_rank: Super Contributor
timestamp: April 20, 2017, 05:23:05 pm
content: Quote from: J4e8a16n on April 20, 2017, 05:13:21 pmThe air gap is there for a reason. Look up air gap transformer using a search engine.

author: MrAl
author_rank: Super Contributor
timestamp: April 20, 2017, 08:12:12 pm
content: Quote from: J4e8a16n on April 20, 2017, 03:22:02 pmHello there,Ferrite dust and some medium like epoxy will not create a longer center leg. It will help, but what you will have created in effect would be a smaller gap, but still a gap. To get rid of the gap you have to use the very same material that the core is made of, and possibly have it oriented in the same magnetic direction as the original center leg. In other words if you had another exact core and could cut off part of the leg and join it perfectly with the original leg you want to alter then you would have effectively no gap. This would be very hard to do obviously. With the 'glue' you propose it will help but will still be a 'distributed' gap which will still be a gap, effectively less of a gap, but will still affect the construction significantly.The other way would be to precision grind the outer two legs so as to remove the space when they are put back together. That takes some good machinery too though.After all is said and done, probably the best bet is to hunt for a new core that has the specs you need.Also, you may want to rethink losing the gap as this helps in some circuits, although that looks like a pretty large gap in that picture.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 20, 2017, 10:10:02 pm
content: Great answer