Why a Burr-Free Round Edge Decides Your Foil Coil
The single most common cause of a turn-to-turn fault in a foil-wound coil is not the design. It is the edge on the material you were sent.
The failure sequence
Foil is wound under tension against interlayer insulation. A burr standing proud of the slit edge presses into that film turn after turn. Nothing is visible during winding. The fault appears at test, after the coil has been assembled and impregnated, and by then the coil is scrap.
The inspection standard
Each roll is checked so that it carries no burrs and no scratches and has a round edge suitable for transformer winding. That check is what the buyer is paying for, more than the metal price.
Surface as well as edge
Surface finish is specified alongside edge condition. A smooth, flat surface reduces eddy current loss in the finished transformer and keeps performance stable under high frequency and high current conditions.
Width tolerance
Width, thickness and length conform to dimensional tolerance limits determined by the transformer design requirement and the relevant industry standard. Agreeing that band before production removes the argument at goods-in.
Protecting the edge in transit
Packing is designed to prevent bending, scratching and other physical damage that would affect performance, using wooden crates or plastic wrapping, with handling instructions supplied.
Applying this to a live design?
Send the dimensions and the target figures and the sales desk will quote the grade that matches.