Mica Tape Insulation

A Layered Insulation Material

The intrinsic electrical and thermal characteristics of mica paper are the basis for mica tape insulation. The mica paper is bonded with a certain quantity of heat-resistant resin and strengthened with materials like glass cloth, polyester film, polyester mat, or polyimide film, depending on the product structure. This hybrid construction guarantees that the tape satisfies the insulation performance criteria of electrical equipment while being suitably flexible for wrapping.

For applications using Vacuum Pressure Impregnation (VPI), material structure is especially important. Glass fabric is utilised for applications requiring great mechanical strength and tear resistance, while polyester film prioritises flexibility. The reinforcement material is chosen based on the necessary mechanical qualities. The mica paper can be manufactured from calcined muscovite or phlogopite.

Low-Resin VPI Performance

Less than 15% resin binder is present in mica tape insulation made for VPI; the normal binder quantity is 10–12 g/m². During the vacuum-pressure process, the goal is to enable the impregnating resin to enter the tape structure. Glass-fabric-reinforced VPI structures typically have a nominal thickness of 0.10–0.18 mm, a total mass of 118–164 g/m², a dielectric strength of 15–25 kV/mm, and a tensile strength of at least 150 N/cm. The range of air permeability is 1600–2500 s/100 ml.

Selection by Electrical System

VPI tape series rated for Class F (155°C) and Class H (180°C) applications are listed in the source. The product line consists of four traditional structures, each matched to a certain function. Polyester film-backed tape is the traditional choice for general-purpose motors up to 11 kV, although polyester felt is preferred for hand-wound coils since its softer handle makes manual layup much easier. High-voltage coils and traction motors, which have stricter criteria for tensile strength and heat resistance, require fiberglass-reinforced material.