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BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961
Posted: 01:02am 03 Sep 2021
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No my friend you didn't come off ungrateful I try to tell new people so they no I am also so very grateful
I had no clue who or what these guy's are capable of when I was new
This place is not like most of the web
You don't have to be very careful who you listen to
If someone talks nonsense someone will set them straight ask me how I know lol
It is more just to let you know like some one did for me that you can trust what these guys say
Sorry I should have made that more clear most definitely my bad
I am good at sticking my foot in my mouth Glad my dogs are trained
I can warn you this stuff is addictive but you already know that
The rating system goes off how much you post like yours saying newbie
Warpspeed has done this likely longer than I have lived
He is rated same or close to me
If you get time go look at most of these guys art work they call a inverter
Unless there is some one new I don't know about I am on very bottom of the list on this site
Really good incredibly talented people on here and then there's me LOL
Have a blessed day my friend Edited 2021-09-03 11:14 by BenandAmberbe warned i am good parrot but Dumber than a box of rocks
teapot Newbie Joined: 22/08/2021 Location: United KingdomPosts: 22
Posted: 05:55am 04 Sep 2021
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No problem, I live with foot permanently in mouth!
I found these two interesting looking inductors in a large scrap Rectifier (48v DC 100A output) Appears to be wound copper strip. Have no idea what the inductance and saturafion currenf is as I have not yet bought an indunctance tester, but I'm guessing from the width and rigitity that it should handle 100A unless too much heat builds up in the core due to resistance and/or saturarion. Worth a hookup and quick look on the scope with modest load do you think?
teapot Newbie Joined: 22/08/2021 Location: United KingdomPosts: 22
Posted: 05:56am 04 Sep 2021
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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 06:08am 04 Sep 2021
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Definitely worth testing. Each looks like two pairs of ferrite E cores.
See if you can find a resonance with a known capacitor. Edited 2021-09-04 16:12 by WarpspeedCheers, Tony.
poida Guru Joined: 02/02/2017 Location: AustraliaPosts: 1418
Posted: 07:28am 04 Sep 2021
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if you have no inductance tester or LCR meter you can make something that will do the job.
Search here and/or ask how.
how I made mine: some pulse generator, 0 to 5V into the Gate of a large MOSFET that had Vg(th) well below 5V. Pulses are controllable from 0 to 10ms wide, with period of about 0.5 second. A CRO or DSO. A DC suppy, 12V at 1 or 2 amps Some large, low ESR caps, 16V 1000uF are cheap and easy to find. Use many in parallel. The current sense in my case is 2 inches of copper wire, about 0.6mm diameter. If using a DSO, you are lucky. Use the average capture mode to squelch noise. And calibrate the current sense wire. You can get quite useful results from this.
Put the caps across the DC input, have the MOSFET switch current into the inductor under test. Measure the voltage across the MOSFET source through the inductor to ground. trigger off the Gate drive.
Again, others here will insist that there are better and more proper ways to do this.
The basic pulse inductor tester will show you inductance and saturation point relative to current.
have a look at https://ludens.cl/Electron/lmeter/lmeter.htmlwronger than a phone book full of wrong phone numbers
teapot Newbie Joined: 22/08/2021 Location: United KingdomPosts: 22
Posted: 09:43pm 05 Sep 2021
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Well I didnt get a lot of spare time this weekend, but I did manage to do some testing of these and various other choke configurations from random components that I was able to obtain.
The best result obtained was with these two chokes in paralell, then obviously in series with the main transformer This halved my idle power (an acceptable 35w but still room for improvement), and made the transformer run quieter.
I then ran a 2.5kW load for approximately 5 minutes. Output waveform was near perfect sine regardless of load. The choke cores remained at near ambient temperatures, the windings only moderately warm (perhaps 40C) but the lead-in cables were very hot (perhaps around 65C). So clearly the cores and windings are a good match (seem to be thick copper strips about 40mm wide separated with some yellow tape - see pics below) but the lead-in cables are not up to the job. They are flimsy 8mm wide or so strips so can't carry high current for extended periods.
As I want my inverter to cope with continuous loads of 2.5kw, and the protective device is at 16A I need it to be able to survive 3.6kW for short periods without burning out. Maybe this will be achievable with adequate fan cooling, but my preference would be to upgrade the lead-ins to these chokes. The outer one should be fairly easy, but the inner one near impossible without unwinding the whole thing.
I did try other choke configurations e.g. different size toroids with different numbers of turns but none were anywhere near as effective as these. Usually a badly distorted output waveform, excessive choke noise, or in one case increased idle current!
The only thing I haven't tried yet is the E-cores recommended by others here. I like these chokes because they are neat and have 4 screw holes for mounting. I can get another pair of them too at no cost.
As an aside,@warpspeed will remember me being concerned as to whether 11 primary turns on my transformer would be sufficient. Well I tried increasing it to 12 turns out of curiousity and the result was slight flattening of the peaks at 2.5kW+ and inout voltage of 22.8V. Some of this may be the result of resistance caused by the choke cables getting hot, but clearly 11 turns was more optimal :).
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:17pm 05 Sep 2021
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That transformer is going to work very well I think.
Any choke will be better than no choke at all, and trying a few different experimental random chokes is something we have all done at some stage. This type of testing can be confusing though, as its not always immediately obvious what is really going on.
For best results, really you need to cobble together a choke saturation tester. It will tell you far more than hit and miss experimentation.Cheers, Tony.
teapot Newbie Joined: 22/08/2021 Location: United KingdomPosts: 22
Posted: 08:13am 06 Sep 2021
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Yes and I remember you or someone else posted a circuit diagram for a simple saturation tester. I will build that and report back once I have some useful data.
Thanks again for your very sound advice! Edited 2021-09-06 18:14 by teapot
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 08:25am 06 Sep 2021
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This has all been a very well trodden and familiar path by many of us here. Sweet running magnetics definitely help make for a robust and reliable inverter.Cheers, Tony.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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