26-10-2016, 09:16 PM
The valve (even if Pentode or Triode) makes it halfwave. The + and - on AC windings simply indicates phase as Terry explained. So if you put 15V + 15V AC from a separate transformer in series in correct phase then you have 30V, or nothing if reversed. Add that 30 one way round to a 220V primary in a German Radio and you now can feed 250V, or if you live in 220V land, and have a 250V primary, you can reverse the 30V and it adds 30V to to 220V to feed the 250V transformer.
Matching phase on modern circuit diagrams (or transformers) is shown as a dot or circle, or if not shown, then OV is the opposite to a dot and the winding end with voltage is "dot". In older times they marked relative phase with + and -, to indicate 0 degrees and 180 degrees, or relative phase the same (zero degrees).
Matching phase on modern circuit diagrams (or transformers) is shown as a dot or circle, or if not shown, then OV is the opposite to a dot and the winding end with voltage is "dot". In older times they marked relative phase with + and -, to indicate 0 degrees and 180 degrees, or relative phase the same (zero degrees).
