Stanley Transformer

Build this to reduce a low bench voltage further. A step-up transformer produces genuinely dangerous voltages from a harmless supply — do not build one on this bench.

Work out I²R for 10 kW delivered at 100 V and at 10,000 V through the same cable. The high-voltage case loses one ten-thousandth as much. That number is why transformers exist.

Stanley claims an annular core whose confronting ends are separated by a VARIABLE gap. Adjusting the gap adjusts the magnetic circuit — a tuning control built into the iron.

Stack insulated sheets into a closed rectangular ring. Closed, so nearly all the flux from one winding threads the other.

Varnish or paper between sheets. Laminations break up eddy current paths; touching sheets behave as a solid core and the transformer runs hot and inefficient.

Wind a known number of turns — say 200 — and record it exactly. The turns ratio IS the voltage ratio, so an uncounted winding is an unknown transformer.

Wind 50 turns for a 4:1 step-down. Keep it insulated from the primary — the two circuits share no electrical connection at all.

Feed low-voltage AC to the primary and measure the secondary. The ratio should match your turns ratio closely. Record the discrepancy.

Apply a steady DC voltage. The secondary reads zero except for a pulse at switch-on and switch-off. Only a CHANGING flux induces voltage — this is why Edison's DC could not be transformed.

Load the secondary and measure both currents. Current goes UP as voltage goes down, in inverse ratio — the transformer trades one for the other, it does not create power.

Compare input and output power. A decent transformer exceeds 95 %, and it does so with no moving parts whatsoever — one of the most efficient machines ever built.

Slip a shim between the core halves. Output falls, because flux now leaks across the gap instead of linking the secondary. This is Stanley's adjustable gap, used deliberately.

Connect two lamps side by side and remove one. The other stays lit at full brightness. Stanley's system put consumers in parallel — the reason one house switching off does not dim the street.

It is warm. That heat is hysteresis and residual eddy current loss in the iron — the price of using a magnetic circuit, and the reason core material matters so much.

The patent. US 349,611, "Induction-coil", granted 21 September 1886 to William Stanley, Jr. of Great Barrington, Massachusetts. Working for Westinghouse, Stanley built the first practical AC distribution system that year, lighting shops along Main Street in Great Barrington from a generator through step-up and step-down transformers. He did not invent the transformer outright — Lucien Gaulard and John Dixon Gibbs had demonstrated one in 1881, and the Hungarian team of Zipernowsky, Bláthy and Déri patented the closed-core parallel-connected design in 1885. Stanley's contribution was the practical, manufacturable form and the working system around it.

Why voltage transformation is the whole game. Resistive loss in a conductor is I²R. Transmitting a given power P at voltage V requires current I = P/V, so loss falls with the SQUARE of any voltage increase. Raising transmission voltage by a factor of ten cuts losses by a factor of a hundred. Direct current could not be transformed — a steady current produces a steady flux, and a steady flux induces nothing — so DC had to be generated near its point of use, which is why Edison's stations served a radius of about a mile. Alternating current with transformers can be generated anywhere and consumed anywhere.

What the device actually does and does not do. Two windings on a shared magnetic circuit exchange energy through flux, not through a connection: the ratio of turns sets the ratio of voltages, and the currents move in the inverse ratio. Power out is power in, less losses. It cannot amplify, it cannot work on DC, and it is one of the most efficient machines ever made — large units exceed 99 % — precisely because nothing in it moves.

Parallel, not series. An equally important choice was connecting consumers in parallel across a secondary rather than in series along a loop. In series, every load affects every other and one failure breaks the circuit; in parallel, each sees the same voltage and can be switched independently. Combined with Tesla's induction motor of 1888, the transformer completed the alternating-current system, and the grid outside your window is still built on these two patents.