Running inductor very hot: DT (°C) = 120 - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: January 09, 2019, 01:13:51 pm
content: Hi folksHave you using high temperature magnetic ?Im doing some math for my electronic load project, and as it is load some losses are even welcomedI want to use choke with calculated worst case DT = 120°CIt is still in safe region by datasheet as booth core and wire used is CLASS 200 so even if use Tamb 55°C have some safety marginMost of loss is in copper and I dont want to add more gauge or strands as it is already relative big and expensive coilAnd at moderate loads are DT around 50°C so totally normal

author: strawberry
author_rank: Super Contributor
timestamp: January 09, 2019, 03:04:18 pm
content: High temperatures are not for reliability , capacitors, PCB, solder joints.. wont benefit being near this inductorI had repaired burned off inductors, if some component in circuit run out of specs/age

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 09, 2019, 03:24:05 pm
content: As strawberry has mentioned, the inductor itself may be safe, but its heat transferred to other components may cause some reliability issues.What type of core are you using? Toroid? EE? PQ?Depending on the geometry, perhaps you could add a heatsink to it.

author: Miyuki
author_rank: Frequent Contributor
timestamp: January 09, 2019, 05:41:41 pm
content: It is EE55 but most of losses are in copper not in core itself so heatsink wont help muchBut I have no space limitation so can leave decent space around

author: james_s
author_rank: Super Contributor
timestamp: January 09, 2019, 07:55:14 pm
content: If you have no space limitation then why don't you use a larger inductor that can carry the current without getting scorching hot? IMHO if a component is getting over 100C then something is very wrong.

author: Miyuki
author_rank: Frequent Contributor
timestamp: January 09, 2019, 08:00:19 pm
content: Because space is free but copper is expensive and I want to keep cost low

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 09, 2019, 08:13:39 pm
content: Often people design so copper losses are about equal to core losses.

author: strawberry
author_rank: Super Contributor
timestamp: January 09, 2019, 09:47:43 pm
content: how expensive copper could be for E55 core, 3eur

author: jbb
author_rank: Super Contributor
timestamp: January 09, 2019, 10:13:10 pm
content: A 120 C temp rise will also be bad for the PCB material itself, and maybe the inductor former/clamp/tape etc.If you want to pursue this, how about mounting the inductor off the PCB and having some flying leads to connect it to the PCB? Ring crimp connectors on the leads and screwed / bolted connectors on the PCB can be very effective.You should also ask yourself what the consequences of a shorted inductor are; blown fuse or cooked PCB or burst into flames or explode and fire shrapnel in your face?

author: viperidae
author_rank: Frequent Contributor
timestamp: January 10, 2019, 04:14:32 am
content: With a delta of 120 and your Tamb of 55, that's getting awfully close to the melting point of solder. Just 13 degrees shy of 60/40

author: coppercone2
author_rank: Super Contributor
timestamp: January 10, 2019, 06:18:48 am
content: i have unscrewed a hot inductor (not this hot) held on by mcmaster stainless screws.I got about 2 grams of rust powder when I undid the bolt. nothing will age well at these temperatures. this is a bad idea.if I found a inductor running that hot I would throw the product out and complain.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 10, 2019, 06:05:55 pm
content: Quote from: Miyuki on January 09, 2019, 08:00:19 pmOkay, how about copper clad aluminum and a huge powdered iron toroid?Tim

author: Miyuki
author_rank: Frequent Contributor
timestamp: January 10, 2019, 06:25:44 pm
content: CCA looks like good option if I found some low volume distributor, it will also offer easier wounding at thicker wire

author: coppercone2
author_rank: Super Contributor
timestamp: January 10, 2019, 06:34:59 pm
content: Quote from: T3sl4co1l on January 10, 2019, 06:05:55 pmhow do you safely solder to this?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 10, 2019, 07:46:28 pm
content: Distributor, Aliexpress.If you order very cheap copper wire there, you may even get it without asking!It's copper clad, so it's solderable. Don't heat it so long the copper plating dissolves and exposes the aluminum core. Don't expect it to be terribly reliable over temperature swings, age and corrosion...Tim

author: coppercone2
author_rank: Super Contributor
timestamp: January 10, 2019, 08:11:47 pm
content: how does that kind of connection break when its soldered? Do the solder bits flake off from the aluminum and leave a open circuit?would anneling the wire of the inductor before soldering help?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 10, 2019, 11:29:03 pm
content: No idea. I would guess the Al-Cu interface layer is brittle and can be prone to peeling apart, especially with corrosion (2000 series copper-based aluminum alloys are notoriously not very corrosion resistant). Thickness of the intermetallic layer will depend on how it was prepared in the first place, and how hot it's gotten, because diffusion. Also, solder is prone to creep, as is the soft aluminum core, making it difficult to secure.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: January 10, 2019, 11:47:01 pm
content: this seems like a bad idea

author: james_s
author_rank: Super Contributor
timestamp: January 11, 2019, 01:15:02 am
content: CCA is garbage. It's cheaper but it has 3X the resistance. Unless you need huge quantities the price difference is just not that significant.

author: fsr
author_rank: Regular Contributor
timestamp: January 14, 2019, 03:16:41 pm
content: I thinked that electronic loads were mostly constant current linear regulators. What's the function of the big inductor running at such temperatures?

author: emece67
author_rank: Frequent Contributor
timestamp: January 14, 2019, 07:05:48 pm
content: .