Impact Loading - PQ Canvass

There are many challenges of impact loading on transformers due to inrush currents from large motors, welding apparatus, and electric arc furnaces. Such currents, while less than short-circuit values, can be significantly higher than a transformer's rated current, leading to early transformer failure or necessitating transformer de-rating.

This paper examines the mechanical stresses on transformer windings, considerations for transformer sizing under impact load conditions, and the use of a PQ Canvass report for quantifying current surges. It also addresses motor inrush current characteristics, the importance of correct transformer sizing, and how to analyze motor starts and transformer sizing under impact loading.