Performance requirements of silicon steel for motors

Silicon steel is an important soft magnetic alloy. The silicon steel used in the generator field is mainly full-process electrical steel with a thickness of 0.50 mm. Some thermal power units use silicon steel or oriented silicon steel with a thickness of 0.35 mm, which is mainly used for stator punching in generators.

Due to the complex structure of the generator and the multi-directional mixed distribution of the magnetic circuit, the generator industry has higher quality requirements for silicon steel, as follows:

A full-process silicon steel sheet
Due to the huge size of the current generator set and the special stacking process requirements, it is impossible to anneal the stator, and full-process silicon steel must be used. For example, the stacked lengths of the stator cores of 300, 600, and 1000 MW turbine generators are 5100, 6731, and 8150 mm respectively. With such a long stator size and a lamination thickness of more than 10,000 sheets, the requirements for the longitudinal and transverse differences between silicon steel sheets are extremely strict.

Three electromagnetic performance requirements are high
Due to the high efficiency design requirements of the generator, the loss of the silicon steel sheet should be as low as possible. The lower the loss, the higher the efficiency of the unit. The efficiency of 300 and 600 MW steam turbine generators must exceed 98%, the efficiency of hydroelectric generators must also exceed 98%, and some small generators must also reach 96%. Therefore, high magnetic induction, high magnetic permeability and magnetic aging are required. The effect is small, and the mechanical properties require good fatigue resistance and low stress sensitivity. Four, good insulation performance
When supplying silicon steel products for generators, major domestic companies that produce high-grade silicon steel use special insulating coating types based on generator performance requirements. The silicon steel products supplied by TISCO to domestic and foreign generator companies usually use C5 or C6 coating; the silicon steel products supplied by Baosteel to the generator industry mostly use H coating and self-adhesive coating; the silicon steel products supplied by Wuhan Iron and Steel to the generator industry mostly use T4 coating or T5 coating.

The interlayer resistance of the silicon steel insulation coating used in large generators can reach more than 10,000 Ω.mm2/p. When generator manufacturers use silicon steel, they often perform secondary painting treatments. Generally, C6 water-soluble paint or organic paint is used. The paint is coated twice. In order to ensure the bonding performance of the two coatings, silicon steel manufacturers are required to use C6 coating.

In short, due to the special performance requirements of generators, there are very high requirements for high-grade non-oriented silicon steel in terms of same-plate differences, electromagnetic properties and coating properties.