Mica Insulated Wires
Rectangular and round copper wires with partial-discharge resistant mica tape; classes 200–240.
Mica, a natural mineral, is the most durable known insulation material against partial discharge (corona). Mica flakes bonded onto a glass-fibre or polyimide carrier are made into tape and wound onto the conductor with overlap. High-voltage generator bars and machine windings exposed to impulse voltage require this structure.
In the mica-over-enamel structure two mechanisms work together: the enamel layer provides inter-turn insulation and low build increase, while the mica tape provides protection against corona erosion and thermal overloads. The mica-based insulation materials used are assessed to the IEC 60371 series.
Mica Insulated Wires Products
Mica-Covered Rectangular Copper Conductor
ISO-CU-MKA-F240
Mica-Covered Round Copper Conductor
ISO-CU-MKA-R240Technical Information
- Mica tape carrier: glass-fibre weave or polyimide film
- Tape width: 15 – 30 mm; overlap 50%
- Thermal class: 200 (N) – 240 (C)
- High partial-discharge resistance and thermal overload tolerance
- Reference: IEC 60371 (mica-based insulation materials), IEC 60085
In motors driven by frequency converters, very short rise-time impulse voltages cause the voltage to distribute unevenly across the first turns of the winding. Under this condition organic insulations erode over time through partial discharge; mica, thanks to its inorganic structure, resists this erosion for a long time.
The mica tape width and overlap ratio determine both the insulation thickness and the efficiency of the winding line. A narrow tape seats more smoothly in tight-radius transitions; a wide tape shortens the winding time in long straight sections.