Lamination Coatings
Lamination Coatings
Electrical steel is usually coated to increase electrical resistance between laminations, reducing eddy currents, to provide resistance to corrosion or rust, and to act as a lubricant during cutting. There are various coatings, organic and inorganic, and the coating used depends on the application of the steel the type of coating selected depends on the heat treatment of the laminations, whether the finished lamination will be immersed in oil, and the working temperature of the finished apparatus.
Very early practice was to insulate each lamination with a layer of paper or a varnish coating, but this reduced the stacking factor of the core and limited the maximum temperature of the core.
ASTM A976-03 classifies different types of coating for electrical steel.
Classification | Description | For Rotors/Stators | Anti-stick treatment |
---|---|---|---|
C0 | Natural oxide formed during mill processing | No | No |
C2 | No | No | No |
C3 | Organic enamel or varnish coating | No | No |
C3A | As C3 but thinner | Yes | No |
C4 | Coating generated by chemical and thermal processing | No | No |
C4A | As C4 but thinner and more weldable | Yes | No |
C4AS | Anti-stick variant of C4 | Yes | Yes |
C5 | High-resistance similar to C4 plus inorganic filler | No | No |
C5A | As C5, but more weldable | Yes | No |
C5AS | Anti-stick variant of C5 | Yes | Yes |
C6 | Inorganic filled organic coating for insulation properties | Yes | Yes |