Industrial Electrical Engg Company

Established since 1921

Mica Therm Tape & Folium

Mica Therm are combination of Mica Paper, Epoxy Novolak Resin and special Woven Glass Cloth of Alkali free. The material is supplied in condition to give tack free but very flexible material which can be wrapped and tapped easily. During the press cycle the resin flows readily as the insulation is consolidated and then cure to give a rigid void free electrical insulation.

The Tapes are supplied with coloured polythene interleaving material in length of 25 & 50 mtrs. The folioums are supplied in 40” width and in continuous roll from of
25 Mtrs./ 50 Mtrs.

APPLICATION: Mica Therm is used for insulating the conductors of stator coils and bars of medium and high voltage rotating machines where class F thermal rating is required.

CURING DETAILS: The thickness of insulation or the numbers of layers in any particular application is determined by consideration of dielectric stress under working and pressure test conditions, and factor compensating for mechanical stress arising during coil manufacture. For general guidance however, a compression factor in moulding of 22 to 25 percent is usually appropriate. For example, one layer of MICA THERM nominally 0.18mm thick, is reduced to 0.13 mm when moulded under a compression factor of 24 percent.

Hence, a slot cell of 3.2mm finished radial thickness would be moulded from 24 thickness or 12 half lap layers of MICA THERM.

Hot press cycles are similarly influenced by a variety of factors such as thermal capacities of press tool and work load, weight of insulation to be pressed etc, but as a rough and ready approximation, coil stacks for
consolidation and require pressing for 15 to 20 minutes at 155 ºC. Similarly, the slot cell of a typical 6.6kv stater coil of up to 15 kilos would require pressing at 1 N/mm² for 45 minutes at 155º C. Similarly, the slot cell or a typical 6.6kv stator coil of up to 15 kilos would require pressing for 45 minutes at 155ºC , followed by an oven post cure at 165º C overnight.

It is usually advisable to remove both consolidated coil stacks and moulded slot cells from the press at working temperature. In the case of coils for operation at higher voltages, long cycles at rather lower temperatures are recommended.

In practice, such essential design details as composition of the tapes or wraps, dielectric stress in operation and press cycles are decisions based on previous experience.

Typical Properties of Uncured material for MICA THERM


Composition Micapaper gsm 120
Bond % 39+ 3
Glass cloth, gsm 35
Nominal Weight gsm 250
Volatile content % 0.7
Nominal Thickness Un pressed



0.12Tensile strength of TapeKN/m14Resin Flow (1 MN/m² at 160ºC On 50 x 50mm sample)% total



We do not guarantee that the users of these materials will attain the same results as we do always, due to varying conditions which may exist in different locations. It is recommended that each user carries out his own tests based on his requirements.


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