The test was carried out according to IEC 60851-4.3.2 and the round bar method was used. The minimum breakdown voltage shall be calculated according to the insulation thickness of each specific fiw wire and in combination with the withstand voltage value per micron in the table below.

The calculation formula of breakdown voltage (BDV) is as follows:

BDV = minimum film thickness * Minimum breakdown voltage per micron

For example: 0.2 mm fiw6, the minimum outer diameter is 0.303 mm

Minimum film thickness= Minimum outer diameter –Nominal diameter = 0.303 mm - 0.2 mm = 0.103 mm = 103 μm

=> BDV = 103 μm x 76 V/μm = 7828 V