Salvaging cores for gate drive transformers - Page 1
Forum section: electronics / general

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 20, 2017, 05:01:20 pm
content: Hi folks!What devices have good a core for a gate drive transformer? I need some cores and I can't buy them here. I have used some computer psu cores but they are horrible. So, I think I might have to do some junkyard diving. Anyone has any idea what devices have good cores for a GDT which reproduces good wave form. I have heard audio amps have good cores in them but I want some other devices so when I go to the junk yard I won't have to return empty handed.Thank!!

author: KhronX
author_rank: Frequent Contributor
timestamp: January 20, 2017, 06:56:33 pm
content: Slightly older / crappier ATX computer power supplies, half-bridge designs (often with beefy BJT's) based on TL494 / KA7500 / SG6105 usually have the PWM controller on the secondary side, and a GDT driving the switching components. If needed, it shouldn't be too big of a deal to re-wind them, i'd think.

author: tautech
author_rank: Super Contributor
timestamp: January 20, 2017, 07:19:01 pm
content: Quote from: MrOmnos on January 20, 2017, 05:01:20 pmDon't you mean Pulse transformer ?Have a look on eBay, there's lots of small ferrite pot core types available.Just be sure to select one that is suitable for gate drive duties and with an adequate isolation rating and the turns ratio you need.

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 20, 2017, 07:24:00 pm
content: Quote from: tautech on January 20, 2017, 07:19:01 pmNope can't do that. No buying from ebay, amazon, alibaba. 3rd world problems.

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 20, 2017, 07:26:48 pm
content: Quote from: KhronX on January 20, 2017, 06:56:33 pmRewinding is not a problem tho, problem is most cores I have tested have produced unusable waveform. I think I have one as you described.It that giant coil you talking about?I pulled out a smaller one and it is cheap stuff. But that giant one looks more like a GDT. It has multiple winding. Is that what you are talking about.

author: bktemp
author_rank: Super Contributor
timestamp: January 20, 2017, 07:35:17 pm
content: T2 was the transformer used for driving the transistors.The large toroidal core is a iron powder core, useless as a gate drive transformer.

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 20, 2017, 07:47:14 pm
content: Quote from: bktemp on January 20, 2017, 07:35:17 pmFound it!This is T2. Will this work? How do I use this this? Where can I find about it internals?

author: bktemp
author_rank: Super Contributor
timestamp: January 20, 2017, 07:56:43 pm
content: http://danyk.cz/s_atx_en.htmlIt is designed for driving BJTs, so for mosfets you probably need to rewind the transformer using more turns for the output windings.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 20, 2017, 09:08:18 pm
content: That should work. The line filter would also be good.Line filters, common mode chokes, etc. have pulse-transformer type cores in them.You should learn how to use transformers -- the math is simple, and you will no longer wonder why some cores work and others don't.Tim

author: Red Squirrel
author_rank: Super Contributor
timestamp: January 20, 2017, 10:59:14 pm
content: I'm new to the world of transformers myself so I could be way off here, but could one use a couple stacked washers to build a simple low power transformer? You'd probably want to isolate them with something to prevent edy currents.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 21, 2017, 12:23:02 am
content: Not with most grades of steel, not very practical. Quite high losses. It would work well enough to demonstrate, but that's about it.The shape is correct for a toroid, though -- they can be made from stacked discs or wound strip. Most are stripwound, because it's easy, of course.Tim

author: tautech
author_rank: Super Contributor
timestamp: January 21, 2017, 03:45:17 am
content: Useful site for more understanding of transformer construction:http://ludens.cl/Electron/trafos/trafos.html