Here’s a reference design that includes a soft power up feature.
https://www.infineon.com/dgdl/Infineon-AN2018-35_EVAL-M1-IM818-A-UserManual-v01_04-EN.pdf?fileId=5546d462677d0f460167bb2df0121ab1 Infineon-AN2018-35_EVAL-M1-IM818-A-UserManual-v01_04-EN PDF Document · 1.7 MB > On Aug 7, 2024, at 7:30 AM, gene heskett <ghesk...@shentel.net> wrote: > > On 8/7/24 03:41, Viesturs Lācis wrote: >> trešd., 2024. g. 7. aug., plkst. 00:21 — lietotājs Chris Albertson >> (<albertson.ch...@gmail.com>) rakstīja: >>> >>> The capacitor is charged when the switch is closed. A huge current will >>> flow into the capacitor until it is “full”. The usual solutions are to (1) >>> use a slow-blow fuse that can withstand the surge current or place a low >>> value power resister in series with the AC to limit maximum current. >>> Inductors can do this better than resistors. >>> >> Yes, the inrush current that charges the capacitor is what I am >> thinking about now. I would prefer taking some ferrite ring and wrap >> the wire around it and be happy but I have no idea if that is how it >> works and I was not able to find any place to explain how to >> calculate. > > ferrite in such a circuit is generally wrong. If the ferrite see's too much > magnetisim it may saturate, at which point it looses its ability to resist > the change and max current will flow according to the ohmage of the wire. It > also has a magnetic curie point, a $5 word that says if this happens above > its curie point temperature, it become austenitic, aka non-magnetic, and can > only be repaired by returning the core to Arnold for a factory heat > treatment. You might want to remember that for some of the high performance > ferrite alloy's, this "curie" temperature is below the boiling point of water > at 100C. That's not hot enough to discolor the paint on it. Moral of the > story is use silicon steel cores for such. > > Initial values are: DC voltage is 340 V, current limit - >> hopefully around 10A, fuse is adjustable, originally set at 12 A (can >> be increased to 16 A). capacitor is 4700 uF. >> How do I calculate the time it takes to [almost] charge the capacitor? > > T=RC will give an answer for (IIRC) a 67% charge. Where T is time in seconds, > R is ohms and C is farads. 5T will give essentially a full charge time. Its > the low R from the powerline that is clearing your fuse/breaker. :o) > >> That would determine that transient state for inductor and then I have >> no idea how to calculate the inductor from here. >> I would prefer inductor because then there is nothing that can break. >> Input is 3 phase AC so I see following drawbacks with introducing resistors: >> 1) putting them after rectifier bridge seems like a violation of "no >> switches in DC bus" recommendation from 8i20 manual. Maybe except by >> having a resistor permanently connected in line and then having a SSR >> in parallel to resistor would be solution. But if SSR fails (I have >> experienced that) how will I know that? All load will go through >> resistor and burn it. > One of the reasons to use a honking high wattage resistor. >> 2) putting them in AC line requires 3 sets of that and the issue of >> the relay that bypasses resistor remains or have I missed something? >> It seems to me that 340V and approximately 10A would require 30-50 ohm >> resistor as suggested by Gene but somehow I am not sure 100W is >> enough. Or is it fine because it is very short period of time? > > That's the theory. In the case of my go704, 3 seconds seems to be enough. > That does not heat a 100 watt R more than 20F. >> Viesturs >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users > > Cheers, Gene Heskett, CET. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
