What is mica?

Mica is the name given to a group of minerals of related composition and similar physical properties, most notably perfect basal cleavage, which means they can be split readily in one plane into a great number of thin, tough laminates.


Where does mica come from?

Mica is mined chiefly in India, Madagascar, Canada, and the United States.


How many types of mica are there?

Of seven common varieties of mica, only muscovite and phlogopite are of any importance to the electrical industry.


What are muscovite and phologopite mica?

Muscovite mica called white or India mica, does have better voltage endurance characteristics than phlogopite. For that reason, muscovite is preferred for motor and generator applications. Phologopite is referred to as amber mica. Phlogopite mica is used for higher temperatures over 600°C. Phlogopite is found in many wire and cable applications, where one must maintain circuit integrity during fire conditions.


Why is mica used for electrical insulation?

It has extremely high dielectric strength, low electric loss, high surface and volume resistivity, excellent thermal stability, and high shear and tensile strengths.


What are some properties of mica?

It is completely inert to the action of water, acids, alkalies, oils and solvents. It is fireproof, non-flammable, unaffected by temperatures of 1200°F, and is resistant to the oxidizing action of electrical discharges.


What is mica paper?

Mica paper is actually a paper like material consisting of miniature flakes of either muscovite or phlogopite mica held together by natural cohesive force between adjacent flakes. This is not to be confused with “cellulose” paper. Mica paper is 100% mica.


What is mica tape?

Mica tape is an inorganic high dielectric tape manufactured with mica paper and laminated to various reinforcing substrates to enable ease of handling. Tapes are available in fully cured, VPI, resin rich (press cure) and B stage.


What are the backings for mica tape?

Backings are woven and non woven glass cloths, non woven polyester web, and various polyester films including polyimide.


What are the advantages of one backing over the other?

The backing is dependent upon the application. For example polyimide film for high temperature applications. The thermal class of the application helps determine the bonding agent and backings selected.


What is a conductor tape? How is it used?

It is the strand insulation used to wrap around the individual conductors. Typically used when turn stresses are elevated beyond standard enamel or daglas over enamel wire coatings.


What is a ground wall tape? How is it used?

Ground wall tape is wrapped around your formed coil, and is used as the major dielectric barrier in the insulation system.


Are mica tapes pressure sensitive?



What is a mica wrapper?

Mica wrapper is a mica roll slit to width to insulate the slot section of a form wound coil.


What does resin rich mean?

Resin rich is B staged or semi cured mica tapes, waiting to be processed in a heated environment.


What is the major advantage and benefit of using a mica tape?

The advantages of mica tape are good dielectric strength, inorganic content, does not support corona, thermal conductivity, low dissipation factor and easily impregnated with resin.


What does the term “flat glass mica” mean?

Woven glass cloth where individual stands are not twisted giving strength while gaining space. The yarns used to produce this flat glass cloth could be compared to ribbon like as opposed to rope like in appearance. The much smoother and more uniform glass cloth allows for additional space in the slot.


What is the benefit of “flat glass mica” over standard mica?

In flat glass mica the flat glass is not heat cleaned so virtually all of its strength is retained, while reducing ground wall thickness over traditional mica tapes using glass cloth.


Any Questions?

Trina Perkins and Wendy Rampy are here to help.

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