The reason for this situation may be due to an excessively heavy load or a mechanical blockage causing a high output current. In the control algorithm of VFD, if the output current exceeds the rated level, VFD will automatically reduce the output frequency. Additionally, it is important to check the motor connections and the V/F curve settings to ensure they are correct, as this can also be a factor causing the increased current that prevents VFD from accelerating when there is a load.