EI-57 Automatic Interleaved Lamination Stacking Machine for Transformer & Adapter Cores Positioned between small EI-48 and larger EI-66 sizes, the EI-57 lamination is one of the most widely used core formats for single-phase low-frequency transformers in the approximate 8-45 VA power band. Our EI-57 stacking machine inserts E and I silicon steel sheets into coil bobbins in a fully interleaved (cross-stacked) pattern, so each E-I joint is staggered on alternate layers. This