When a transformer is first energized or reenergized after a short interruption, the transformer may draw inrush current from the system due to the core magnetization being out of sync with the voltage. The inrush current may approach short-circuit levels, as much as 40 times the transformer's full-load current.

What causes inrush current in a transformer?

Inrush Current is a form of over current that occurs during energisation of a transformer and is a large transient current which is caused by part cycle saturation of the magnetic core of the transformer. For power transformers, the magnitude of inrush current is initially 6 – 10 times the rated load current.

Do transformers have inrush current?

A transformer draws inrush current that can exceed saturation current at power up. The Inrush Current affects the magnetic property of the core. ... If turn-on occurs when the AC voltage wave is at its peak value, there will be no inrush current drawn by the transformer.