Grain-oriented electrical steels for power and distribution transformers

Grain-oriented electrical steels (GOES) are silicon steels and are used in power distribution networks as transformer cores. The main magnetic properties required are high permeability and low core loss. Hysteresis losses and eddy current loses are both part of the core loss. Eddy currents are reduced by stacking strips of thin, electrically isolated material and increasing the resistance by adding silicon and aluminium. They are cold rolled to around 0.3-mm thick. Hysteresis loss arises from the formation of domains and grains not oriented in the rolling direction; hence the grains must be oriented in the < 100 > direction. These grains are also known to be goss texture grains. This article will cover the basics of the properties required for GOES and how the chemistry and process affect these properties.