Kool mu torroid inductor will dissipate 5.4W of core loss - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: March 31, 2022, 11:04:59 pm
content: Hi,We are doing a 2.5kW Boost PFC , 180VAC to 265VAC.The PFC inductor is to be two stacked 77778A7 torroids. These are to be wound with 18 turns of 7/0.3mm TEX-ELZ wire.L will be from 275uH to 169uH.This PFC inductor will be doubled up on…and the PFC will switch from one inductor to the other every 10ms, to reduce dissipation in the inductor(s)This means that the core loss of this stacked inductor will be 5.4W, and the windings loss will be 3W.Would you think this stacked inductor can handle this kind of power dissipation?LTspice and calc doc attached77778A7 torroidhttps://www.mag-inc.com/Media/Magnetics/Datasheets/0077778A7.pdf7/0.3mm TEX-ELZhttps://www.furukawa.co.jp/tex-e/en/product/texelz.html

author: uer166
author_rank: Super Contributor
timestamp: April 01, 2022, 10:17:29 pm
content: Switch inductors every 10ms? What? Why not just make it a 2 phase interleaved PFC instead of over-sizing each of the inductors by a factor of 2? You've basically created a primitive interleaved converter with none of the benefits of real interleaving.

author: Faringdon
author_rank: Super Contributor
timestamp: April 02, 2022, 01:04:31 pm
content: Thanks, though its much simpler. the torroids can be undersized a bit because they are not saturation limited anyway...its core loss limited.Once rev eng'd a 3kW offline batt charger from a reputable co, and this is how they were doing it.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 03, 2022, 12:11:05 am
content: Take a look at "bridgeless PFC".

author: Faringdon
author_rank: Super Contributor
timestamp: April 06, 2022, 10:08:51 pm
content: Thanks, but this is just a prototype and to be done as cheap and quick as poss.For the PFC of 4.5kW from 180VAC (60KhZ switching frequency)An inductor of 173uH is needed at the peak current (43A).This means using seven stacked Micrometals MP-300147-2 torroids with 23 turns....and three of these inductors will be needed, and they will share 10ms "slots" (each inductor takes every third 10ms slot)Do you know how we can best stick these 7 torroids together?....in the first place, i am just thinking some blu-tak and then nylon fishing line.....and then the 5 stranded turns of TEX-ELX 7/0.3mm will finally hold the seven torroids in a stack?

author: uer166
author_rank: Super Contributor
timestamp: April 06, 2022, 10:37:10 pm
content: Quote from: Faringdon on April 06, 2022, 10:08:51 pmI'd like to see this when it works (or doesn't). This means that each inductor would have to provide the 4.5kW peak when it's operated in its' slot, and the output caps need to handle the entire ripple current of the boost output (which is the 43A peak at 60kHz). I'd be very impressed if this assembly somehow works with reasonable thermals and size.

author: Faringdon
author_rank: Super Contributor
timestamp: April 07, 2022, 01:53:36 pm
content: QuoteIve seen this done at 3kW....for a EV battery charger...they used two pfc stages in 10ms slots.......so 1.5kW each....i'm doing the same, 1.5kW....but in three slots to make the 4.5kW.The battery charger was a reputable European company one.I ran it with a small room fan generally blowing over it and it was ok.........i saw on the car there was a hot plate that it was supposed to be screwed to..........this may have had fans blowing over it i dont know...or may even have been water cooled....but i ran it without the hotplate, on the wooden table, and with just a small room fan generally blowing over it, at 3kW