The key factors are transformer design (core/coil size), losses (copper, iron), load type (lagging/leading power factor), and sizing relative to load.

Lower regulation corresponds to better transformer performance. Most applications require regulation within 3-5%.

Theoretically, an ideal transformer would have zero regulation. However, in practice 0.5-2% is considered excellent regulation.

Positive voltage regulation occurs when the secondary voltage drops under load, while negative voltage regulation occurs when the secondary voltage increases under load.

Zero voltage regulation is an ideal condition where the secondary voltage remains constant from no-load to full-load, but it is difficult to achieve in practice.