dot-polarity-sum-three-row-scan - Electronic Circuits XV & XVI: Transformers and Switched-Capacitor Conversion Step by Step

Transformer dot polarity tells whether two winding voltages add or subtract when they are combined at an output. The rows use exact ideal winding voltages and sign conventions; real measurements also depend on winding orientation, leakage inductance, parasitic capacitance, phase shift, probe reference, and measurement uncertainty.

Dot polarity rows separate cancellation, addition, and difference. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Dot polarity chooses addition or subtraction

Every polarity row cites two distinct winding-voltage sources before computing output.

V_{\text{out}}=V_a\pm V_b

Three polarity rows separate cancel, add, and difference

Equal opposing windings cancel, equal aiding windings add, and unequal opposing windings leave a difference.

\begin{array}{c|c|c|c}V_a&V_b&\text{mode}&V_{\text{out}}\\4\ \text{V}&4\ \text{V}&\text{opposing}&0\ \text{V}\\4\ \text{V}&4\ \text{V}&\text{aiding}&8\ \text{V}\\6\ \text{V}&4\ \text{V}&\text{opposing}&2\ \text{V}\\\end{array}

The final polarity row subtracts the cited winding voltages

The displayed difference is not a free label; it cites the two winding rows and the opposing sign rule.

6\ \text{V}+\left(-4\ \text{V}\right)=2\ \text{V}