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| Isolation transformer with a high voltage winding... how to handle it? |
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| mlefe:
Can you help me understand why it saturates it? Can you point me at where I can learn a bit more about this effect? Putting limiting resistors make sense or the whole thing won't work no matter what I do? (I'm sure I haven't seen the effect because I've used a very low 6VAC to test the thing and never connected it to mains) |
| mlefe:
--- Quote from: thm_w on August 24, 2018, 09:32:42 pm ---It seems to just have a few buck/boost taps, based on the Vin vs Vout graph: http://stop-tarif.ru/shema-apc-line-r-1200.php So is OP connecting 120V across the ~10V taps? That would explain where the 700V is coming from. From what I see from example buck/boost transformer schematics there is only one high voltage winding and a number of low voltage windings. I don't think this transformer will work for what OP wants to do. --- End quote --- I believe this version works in a similar way, but has some differences in the components (I see some things populated in mine that I'm not seeing in the pictures mentioned in post) I'm uploading a picture of my version, in particular, there's a big white cap where in the link shows a smaller yellow one. |
| tkamiya:
I'm sure you will be encasing the whole setup in a suitable insulated case. If that is the case, what you propose is safe. Just make sure you use materials that can withstand the voltage to isolate that high voltage wires. Having said that, I'm not sure if it's safe for YOU. US being tinklers, I would imagine you'd be opening that box from time to time. Possibly in a hurry and mind elsewhere. You'd be now faced with that high voltage. Perhaps you've forgotten it's there by this happens? By looks of it, the transformer does not appear to be that large. At least in US, isolation transformers are cheap and plentiful. (smaller ones are....) I had potentially fatal high voltage encounters before. I never thought I would but I did. I think, if I were in your position, I'd just get a proper transformer, a larger one, and construct the isolation box. Then save that 700v transformer when high voltage is necessary. |
| ArthurDent:
Here's my theory #2. The 770 volts you assumed never made much sense no matter what the transformer type was. You were testing the transformer properly to get ratios but you weren't sure which winding was which. What I 'think' now is explained in the simple schematic below. What you believed was a 770 volt winding is actually the 110 (or 120) volt winding. This makes the 2 identical windings about 16 volts each and these were used to power the circuitry and relays. The heavy leads were low voltage secondary windings that would either subtract or add to the line voltage wired in series through the relays, depending on the phasing of the windings. thm_w was close in their explanation but you were only doing low voltage ratios not putting line voltage on a low voltage winding. Check this out and see if it makes sense and see if you can power what you thought was the 770 volt winding as the primary through a 40 watt bulb for protection and if it doesn't light up, this is probably correct. If it is correct, this cannot be used as an isolation transformer but could be used like a buck/boost autotransformer. |
| Jwillis:
Are you sure that isn't an auto transformer.Since the secondary shares the neutral of the primary and can be a single winding with taps. that means that all wires are the same gauge . If you run your voltage into secondary the primary will become very high voltage and other secondaries can be the same as the input voltage.If it is an auto transformer it won't be very good for isolation. Check continuity between taps .If you get continuity between suspected secondaries and suspected primaries then you probably have an auto transformer. |
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