# What is the tap on a center tap transformer

How exactly is a tap made. I just got curious I've seen the circuit diagram and they often say things along the lines of "a wire is attached in the exact middle of the secondary winding". But how? Might be a dumb question but I can't really find any pictures of how it's done, is it just soldered halfway? Is it looped on there in such a way to only influence one spot?

• What size of transformer are we talking? For a PCB mounted one you terminate your winding halfway to a pin, new wire and continue from the same pin. Effectively two separate windings with one common electrical connection. – winny Oct 1 '18 at 21:02
• @winny, what about for a much larger winding not attached to a pcb? – Anonymous3.1415 Oct 1 '18 at 21:05

A center-tap transformer is designed to provide two separate secondary voltages, VA and VB with a common connection. This type of transformer configuration produces a two-phase, 3-wire supply.

The secondary voltages are the same and proportional to the supply voltage, VP, therefore power in each winding is the same. The voltages produced across each of the secondary winding is determined by the turns ratio as shown.

See here is good video to how center tapped include and equally winding on both output side.

• The OP's question is how its done physically, not the electrical properties. If this information is in the video, you should summarize it, so we don't need to watch the entire 7 minutes. – user71659 Oct 1 '18 at 20:40
• Thank you the link was directly to someone actually making one, that's what I was looking for in terms of how it is physically connected. I just needed to see it for my own understanding – Anonymous3.1415 Oct 1 '18 at 21:09

If you don’t care about winding patterns, a balanced Center tap can be easily made with a wire pair.

Connect opposite one end of each wire so that the current direct is inverted physically but magnetically and logically from end to end now flows in the same direction with the same flux polarity in the core.

With the same length wires and same radius to core, this yields a balanced inductance for a centre tap which is important for preventing FLUX WALK saturation in some cases in high current SMPS where there is no dead-time* in commutation. (not ideal*)