The determination of the Partial Discharges Inception Voltage (PDIV) of the different configurations in electrical motors is essential to ensure the sizing and to choose the right electrical insulation system. For that, the standard IEEE 117-1974 suggests the using of the motorette. Measurements performed on this model show the good reproducibility of the results for non-impregnated and impregnated motorettes. The determinations of the PDIV have also been done using the Paschen's law modified by Dunbar. PDIV resulting from experimental measurements are in good accordance with those obtained by the modeling.