Adequately protecting and sizing equipment is a must for safe, reliable, and cost-effective projects. While it’s common to focus on sizing individual components, a better approach involves looking at the working system.

When you need to use a step-up transformer to boost primary voltage to a higher secondary voltage, the inrush current is large. This can stress the primary overcurrent protective device. The protection scheme should be designed to withstand and operate through the large inrush currents of step-up transformers.