The invention relates to coated motor insulation films with improved resistance to corona in electric fields. Electric motors (transformers, motors, generators) have complex insulating systems depending on their performance and design principles. Here, thin film materials are used as insulators in different areas. Film insulating materials include thermoplastic or chemically cross-linked polymer films. A reasonable number of membrane materials can be considered to meet the mechanical, electrical and thermal requirements. In the case of electric motors and generators, the corresponding films are wrapped around the conductor in order to insulate all and part of the conductor. Corona-resistant PI films are available for partial conductor insulation. The film is very expensive and is available from only one manufacturer.
For all insulation, a mica-coated motor insulation film surface material can be considered. This solution is also expensive and difficult to work with. There is a risk of mica particles falling off in the coil. For polymer films, i.e., as a carrier for mica particles, PET (polyethylene terephthalate) films, PEN (polyethylene naphthalate) films and PI (polyimide) films are mainly used.
The disadvantage of prior art solutions is that the resulting coated motor insulation films are difficult and expensive to handle. For example, the bending radius of the mica-coated film is small when winding around the conductor, because otherwise the mica would fall off. In insulators according to the prior art, coated motor insulating films are usually impregnated with resin after winding due to mechanical stability, or in the case of materials containing mica, the semifinished product is already impregnated with resin (so-called use of resin-rich materials), so there is a risk of defective areas in the impregnated resin, which reduces the resistance to corona and thus threatens the continued reliability of the insulation. Therefore, the task of the invention is to produce an insulator for electric motors, especially transformers, electric motors, generators, which have improved corona resistance in well-insulated motors.