open-secondary-draws-no-ideal-load-current - Electronic Circuits XV & XVI: Transformers and Switched-Capacitor Conversion Step by Step

An open-secondary-draws-no-ideal-load-current scan treats the open secondary as a boundary case: the load branch is open, so secondary current and primary load current stay at 0 A in every row. The arithmetic is exact only for the stated open-load labels, turns counts, voltages, currents, powers, and rows in the ideal transformer, perfect-coupling, no-magnetizing-current model. Real transformers add winding resistance, leakage inductance, core loss, magnetizing current, load tolerance, probe/calibration limits, finite precision, and measurement uncertainty.

Open secondary means no reflected load current in this ideal model. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Open secondary means no ideal load branch

The ideal open case is a boundary row: reflected load current is zero, while magnetizing current stays out of this model.

R_s=\text{open}\quad\Rightarrow\quad I_s=I_{p,\text{load}}=0\ \text{A}

Finite loads draw current; the open boundary does not

The scan separates an open secondary from finite resistance rows.

\begin{array}{c|c|c|c}R_s&I_s&I_{p,\text{load}}&P\\\text{open}&0\ \text{A}&0\ \text{A}&0\ \text{W}\\6\ \text{ohm}&1\ \text{A}&\tfrac{1}{2}\ \text{A}&6\ \text{W}\\3\ \text{ohm}&2\ \text{A}&1\ \text{A}&12\ \text{W}\\\end{array}

An open secondary has zero ideal reflected/load current

The check says zero reflected/load current only. It does not claim zero total primary current; real magnetizing current is out of scope.

I_s=0\ \text{A}\quad I_{p,\text{load}}=0\ \text{A}\quad P=0\ \text{W}