Unserstanding of "Maximum repetitive peak isolation voltage"
For sinusoidal stress voltages, VIORM and VIOWM are equivalent i.e. repetitive voltage and withstand voltage are the same.

However, when the working voltages are not sinusiodal (like in some inverters and motor drives) the lower "repetitive" value represents all types of waveforms that could be present.

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High-voltage reinforced isolation: Definitions and test methodologies

Written by Anant S Kamath and Kannan Soundarapandian from TI (see page 3).