Auto Transformer Factory & Supplier Serving Sri Lanka

As Sri Lanka accelerates its infrastructure modernization, upgrading the nation’s 33 kV primary distribution spine and 11 kV secondary networks requires high-efficiency power equipment. Auto Transformers (Autotransformers) offer a decisive engineering advantage over traditional dual-winding transformers due to their electrical auto-coupling mechanism, significantly lower core/copper losses, reduced physical footprint, and superior voltage regulation characteristics under varying load power factors.

Unlike conventional double-wound transformers where energy transfer occurs purely through magnetic induction between galvanically isolated primary and secondary windings, an Auto Transformer utilizes a single continuous magnetic winding wound on a high-permeability Cold-Rolled Grain-Oriented (CRGO) silicon steel core. By sharing a common winding section between the high-voltage (HV) and low-voltage (LV) circuits, the unit transfers a substantial portion of power via direct electrical conduction, leaving only a fraction of the rating to be transferred inductively.

This fundamental physical principle results in dramatic material savings in electrolytic copper conductors and core laminations. For step-down applications where the voltage transformation ratio $r = V_{LV} / V_{HV}$ approaches unity (e.g., transforming 33 kV down to 22 kV or 11 kV to 6.6 kV within Sri Lankan utility interconnects), the required physical rating $S_{auto}$ scales directly with the equivalent rating $S_{double}$ according to the co-axial power ratio equation:

This thermodynamic and electromagnetic leverage reduces copper volume by up to 45%, decreases total no-load ($P_0$) and load losses ($P_k$), and optimizes voltage regulation across heavy industrial feeders in Katunayake, Biyagama, and Hambantota.