29-12-2011, 07:09 PM
(29-12-2011, 05:51 PM)Bushbaby Wrote: I'm no expert when it comes to transformers.
Rob
O.K. ~ what follows may help . . .
Basic L.F. transformer operation is fairly straightforward: as I said above, the particular one you have there is giving you an 'introductory baptism of fire'. :omg:
I assume that you are familiar with the basic fundamental law of volts in / volts out = primary turns / secondary turns. What confuses many people, with a transformer, such as yours, is the issue of 'phase'. IMHO, 'phase' is a word that is probably mis-used and misunderstood more than any other word in the fields of electrics / electronics (with the possible exception of 'decibel'
). The word 'phase' gets banded around as though it is some absolute quantity: it isn't! Like 'voltage', 'phase' is relative to something. Take a simple transformer with one secondary winding: one end of that winding is 180 degrees out-of-phase with the other: think of that as when one end 'pushes' the other end 'pulls'. Then half of one cycle later, what was 'pushing', now 'pulls', and vice-versa. Now with two separate secondary windings, what this means is that when we connect them together, we have to be sure that all the 'pushes' and all the 'pulls' are working together at the same time, if we connect the two windings in parallel. However, if we join the windings the 'other way round', so that when one end of one winding is 'pushing', the corresponding end of the other winding is 'pulling' - so the voltages across the two windings are 180 degrees out of phase . . . then the voltages from the two windings will add up. If we had connected those two windings the 'wrong way round' then the resultant output voltage would be zero, since when one is 'pushing', the other is 'pulling'.It is usual to denote the 'in-phase' windings on multiple secondaries with a dot - as I have done. In practice, the actual phase relationships between any number of secondary windings can most easily be determined by voltage measurements of those voltages. When I do that, I usually mark all the corresponding 'ends' of windings with a mark of some sort - such as a dob of 'Tippex' - so that I then know for sure when I come to use the transformer.
HTH.
Al.
