Method of manufacturing a lamination stack for use in an electrical machine

A method of manufacturing a lamination stack for use in a rotating electrical machine, the method comprising:

• providing naked sheets made of ferritic material;
• preparing both sides of each naked sheet to obtain a determined surface roughness;
• coating at least one roughened side of each naked sheet with a chemically protective electrically insulating material;
• stacking the coated sheets;
• compressing the stack of coated sheets;
• heating the compressed stack of coated sheets at a temperature above a melting temperature of the chemically protective electrically insulating material;
• and
• cooling the compressed stack to form an integral lamination stack comprising sheets of ferritic material alternating with layers of the chemically protective electrically insulating material,
• wherein the coating at least one roughened side of each naked sheet comprises:
• a. dispersing the chemically protective electrically insulating material on the roughened surface of the each naked sheet, the chemically protective electrically insulating material being in the form of solid powder,
• b. then heating the each sheet having the chemically protective electrically insulating material dispersed thereon to a temperature above the melting point of the chemically protective electrically insulating material, and
• c. then cooling the each sheet having the melted chemically protective electrically insulating material thereon in ambient air.

A method of manufacturing a lamination stack for use in a rotating electrical machine, the method comprising:

• providing naked sheets made of ferritic material;
• preparing both sides of each naked sheet to obtain a determined surface roughness;
• coating at least one roughened side of each naked sheet with a chemically protective electrically insulating material;
• stacking the coated sheets;
• compressing the stack of coated sheets;
• heating the compressed stack of coated sheets at a temperature above a melting temperature of the chemically protective electrically insulating material;
• and
• cooling the compressed stack to form an integral lamination stack comprising sheets of ferritic material alternating with layers of the chemically protective electrically insulating material,
• wherein the preparing both sides of each naked sheet comprises immersing each naked sheet in a hydrofluoric acid bath.