Ageing and the Life Curve of Type II Turn-to-Turn Insulation under Repetitive Impulse Energization: Effect of Switching Frequency

In this paper life curves for Type II turn insulation are developed under repetitive square impulse voltage stresses instead of sinusoidal ones. This work aims to verify and understand the influence of the switching waveform frequency on the life of machine turn insulation and provide the foundation on which to establish a standard reference life curve for such types of supplies. The developed life curves in this paper, both at 1 kHz and 4 kHz switching frequency, suggest a non-linear switching frequency effect and advocate a different endurance coefficient for turn insulation life curve from the one currently in use based on the IEC 60034-18-42 standard.