Designers must balance electrical, thermal, mechanical, and economic factors. Key aspects include voltage and kVA ratings, insulation levels, short-circuit withstand, losses, temperature rise, cooling method, noise limits, and transport constraints. Materials selection, core geometry, and winding arrangements are optimized for efficiency and reliability. Standards compliance, environmental conditions (altitude, ambient temperature, pollution), and special requirements such as seismic or fire performance also shape design choices. Tap changer range, monitoring provisions, and maintainability round out the engineering tradeoffs.