Electrical steel, also known as transformer steel, is an alloy of iron and silicon used to build transformer cores, stators of generators and motors. It retains heat and prevents magnetic eddy currents. Grain-oriented silicon steel produces a stable magnetic field, while non-oriented silicon steel is used in motors or generators. Grades of electrical steel are defined by the level of core heat loss, and insulation can be applied through oxide, enamel, or varnish coatings.
Electrical steel is an alloy that contains iron and silicon. It can be manufactured to be 15% silicon, depending on what the finished product will be. Also called transformer steel, this type of steel is most often used to build the cores of transformers as well as the stators of generators and motors. It’s also efficient at retaining heat so high temperatures won’t affect the performance of items, such as power lines and manufacturing machinery, where keeping temperatures low is important for energy efficiency and equipment longevity.
Heat loss in electrical steel is avoided due to entrained silicon. This increases the so-called resistivity within the steel, which prevents magnetic eddy currents that cause a build-up of runaway heat. Performance also improves when larger grain sizes are used to produce silicon steel. The heat treatment of the steel during production accomplishes the task of creating a larger grain size.
The grain structure itself can be oriented to suit certain tasks. In grain-oriented silicon steel, the grains all point in one direction, which means that the molecules have the same polar orientation. Electrical steel produces a stable magnetic field, making it safe to use in power transformers and other applications where stable electromagnetism is important. When the required magnetic properties need to be less structured, non-oriented silicon steel can be used, such as in motors or generators.
Electrical steel is sold in grades, each grade is defined by the level of core heat loss. An example of such a grade is M19, where this loss is relatively low, making the material suitable for use in motion control systems. High loss steels are offered in grades such as M43 which are not necessarily heat treated or annealed, to relieve the stresses on the material caused by the manufacturing process.
The performance of electrical steel is further improved by insulating it. An oxide coating can be applied during milling, and while this is the cheapest way to insulate the steel, the coating doesn’t withstand stress too well. Enamel or varnish coatings offer the advantage of good insulating properties, but heat treatment is not possible after the product has been manufactured. Higher quality coatings are more versatile and withstand higher temperatures, but if the insulation is strong enough it can cause excessive wear on the tools used for working steel.
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