Electrical Engineering : Power Transformer Design Concepts

Design core and winding concepts for power transformers, cover core types, materials, and voltage patterns. Learn winding configurations, coil types, cooling, tap changers, and size calculations.

Explain creepage and electrical jump, their roles in preventing flashover between high and low voltage windings, and how gaps, pressboard, oil insulation, and air clearances vary by KB class.

Explain on-load and off-circuit tap changers, how they control transformer voltage by changing turns, and compare linear, bent, reversing, and coarse-fine arrangements.

Compute a transformer's impedance voltage using pi times ampere-turns times sigma dm, define dm as the sum of ampere turns between windings, and determine percent impedance with coil placement considerations.

Compute core weight from total core length, cross-section, and core density; estimate no-load iron losses with a core-building factor; then compute copper winding weights from copper density and winding lengths.

This lecture explains transformer load losses, including ice core loss, winding copper loss, and stray losses, with i^2 r losses depending on current, resistance, length, and cross section.

Design and assemble the core and coil assembly as the transformer heart for operation, set radial and axial gaps, include regulating windings, and prepare leads for bushing connections.

Analyze transformer oil as the key dielectric and cooling medium, governed by IEC 296, IS 335, and BS 148 standards, comparing mineral oil with the easter oil for subzero conditions.

Design a mild-steel transformer tank housing the core, winding, and oil with dimensions set by the core, windings, and tap changer, and mount bushings or a cable box for three-phase.

Understand how to specify condenser bushings for transformers, including 60 kV and above, ensure impulse voltage handling and reliability, and choose bushing make and ratings as the purchaser.

Examine temperature gradient in transformers and compare natural oil cooling with radiators to forced cooling. Note how cooling ratings, water cooling, and load losses influence winding and oil temperatures.

Understand how transformer voltages divide into electromagnetic and non-linear impulse components, with interleaved shielding to provide uniform impulse distribution, and learn short-circuit forces, winding design, and software-based analysis.