Martin, I wonder why there should be no air gap?
- Paul On Wednesday, September 1, 2021 at 1:55:30 AM UTC-4 Dekatron42 wrote: > Paul, > > I'll ask him, but a quick search at Digikey showed both some RM10 and > ETD29 cores, but only a few. Finding Ferrite cores today is not easy, I > have searched some for other projects and they aren't usually stocked in > the ranges that the manufacturers make them, and if you want something > outside what is available in stock it becomes very expensive as you'll have > to by thousands if not more. I usually try the ones they have and have to > live with that since I can't buy the thousands needed to get the perfect > one. I'll ask Ed to have a look and see if any of the ones that are stocked > will do - just remember that they will have to be the transformer type > without an airgap between the center pieces to work in this application. > > /Martin > > On Wednesday, 1 September 2021 at 04:26:30 UTC+2 Paul Andrews wrote: > >> >> Hi Martin >> >> I tried to find a suitable core at digikey, but their parameters don’t >> map very well to the equation that Ed gives. Could he take a look at what >> they have and perhaps recommend something. For simplicity’s sake I just >> looked at toroids >> https://www.digikey.com/en/products/filter/ferrite-cores/936?s=N4IgTCBcDaICoHsBOCCWATAhgGwAQGNkBTAZxAF0BfIA >> >> Thanks - Paul >> On Friday, August 27, 2021 at 8:45:56 AM UTC-4 Dekatron42 wrote: >> >>> Since transformers isn't my best area, I only have basic understanding >>> of the intricacies but I have experimented some with different transformers >>> in different cases like when driving Trochotrons and Dekatrons I decided to >>> ask an acquaintance who has worked with transformers. His name is Ed >>> Dinning, I got to know him over at the UKVRRR forum (UK Vintage Radio >>> Repair and Restoration forum: https://www.vintage-radio.net/forum/), he >>> told me you are welcome to contact him via me so that his email is somewhat >>> protected - if you ask him anything related to the VFD-drivers it would >>> be kind if you could post something here in this forum so we all can learn >>> from it. >>> >>> This is his answer to my question on what transformer to chose for the >>> driver in the article, it sure helped me and I hope it helps anyone who >>> wants to experiment with this driver: >>> >>> "Hi Martin, as it operates about 50/100KHz virtually any ferrite should >>> do. It should be a transformer type with no air gap. >>> The turns are normally based on the transformer equation for square waves >>> >>> N= V/ 4 * F * B* Ae >>> >>> N=turns, V=volts F=frequency,B= flux density, typically 200/250mT for a >>> ferrite, Ae the centre pole area in M^2 >>> >>> The actual losses come out later on in the design process and are not >>> part of the initial criteria >>> >>> Copper sizing is normally based on 3A per mm^2 of cross sectional area >>> >>> The turns figure he gives looks about right for something like an RM10 >>> core, or you could try an EE25 or an ETD29 core in sat F44 materials >>> ETD's are the core of choice for this type of application and should be >>> readily available. >>> >>> The more turns that are used the lower the iron losses and the cooler >>> the core runs, but the copper losses increase unless fatter copper is used. >>> Skin effect will be of minor importance at your frequency >>> >>> It would also work on a normal laminated core at 50Hz which should not >>> be too big as you can run that at up to 1.5T flux density. >>> Regulation could be a normal type of regulator set for constant current. >>> >>> Always many choices in Engineering >>> >>> Cheers, Ed >>> >>> Ed Dinning Retired Engineer" >>> >>> /Martin >>> >>> On Wednesday, 25 August 2021 at 23:02:48 UTC+2 Paul Andrews wrote: >>> >>>> When I have time, I will try the driver at the link Martin gave ( >>>> http://www.nutsvolts.com/media-files/Forum-Articles/QA_201110.pdf), >>>> but without the transformer initially. As far as I can tell, the >>>> transformer is just to make the VFD drive isolated so you can pull it up >>>> above ground. >>>> >>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/fe0bd694-52af-47ce-b3fd-50e5f75a9799n%40googlegroups.com.
