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| Is a triac on the primary side of a transformer a good idea? |
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| daubmaso:
Oh okay, thanks! |
| james_s:
--- Quote from: lordvader88 on April 28, 2018, 10:38:39 pm ---Here on The Rock it's 120V --- End quote --- It has crept up over the years, I believe to extract a bit more capacity from the grid. US and Canada are the same spec, at one point it was 110/220V, then 115/230V, then 117/234V, then the current 120/240V. Many people colloquially refer to it as "110" or "220" even though that hasn't been the standard in decades. For anyone confused by the double voltages, we use a split phase that comes off a transformer with a grounded center tap, 120-0-120V. The standard residential branch circuits are 120V but major appliances like ovens, clothes dryers, water heaters and other large loads are 240V. |
| Circlotron:
--- Quote from: james_s on May 01, 2018, 02:56:54 am ---For anyone confused by the double voltages, we use a split phase that comes off a transformer with a grounded center tap, 120-0-120V. The standard residential branch circuits are 120V but major appliances like ovens, clothes dryers, water heaters and other large loads are 240V. --- End quote --- So the transformer secondary out in the street has a centre tap and 6 free ends? Effectively a star config and a second star shifted 60 deg. That's be cool! 6 different phases to neutral and a further not sure how many from phase end to adjacent phase end. |
| oldway:
Regarding the use of your transformer to make a DIY symmetrical +/- 1.5 to 20V adjustable power supply with LM317 and LM337, I think it is possible, despite the reduced power of the transformer. You should know that a transformer has a fairly long thermal constant, it takes between 15 minutes and 30 minutes for it to reach its equilibrium temperature ... It can therefore been overload for a short period of time without risk. On the other hand, you can increase its power by improving its cooling, for example by forced ventilation or cooling in the oil. And, finally, it is a small transformer of low value, the possible overheating will reduce the useful life of the transformer ... But who is worried about it? |
| james_s:
--- Quote from: Circlotron on May 01, 2018, 10:18:28 am --- --- Quote from: james_s on May 01, 2018, 02:56:54 am ---For anyone confused by the double voltages, we use a split phase that comes off a transformer with a grounded center tap, 120-0-120V. The standard residential branch circuits are 120V but major appliances like ovens, clothes dryers, water heaters and other large loads are 240V. --- End quote --- So the transformer secondary out in the street has a centre tap and 6 free ends? Effectively a star config and a second star shifted 60 deg. That's be cool! 6 different phases to neutral and a further not sure how many from phase end to adjacent phase end. --- End quote --- No, it only has a single secondary with a center tap that is tied to earth, so 3 wires coming out. From one side you get 120V to neutral, from the other side you get 120V to neutral and from live to live you get 240V. The disadvantage of this setup is that 240V circuits have two lives but in practice it does work fine. |
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