Current Harmonics Generated by Medium Voltage Soft-Starters Based on IEEE 519:2014

The use of medium voltage soft-starters for starting large motors is common in the industrial environment. These soft-starters, comprising SCRs in their topology, can significantly impact the power quality of the grid. This study evaluates the current disturbances introduced by a typical soft-starter during motor startup, based on the recommendations outlined in IEEE 519:2014. The analysis focuses on two specific configurations, one involving a 4.16 kV, 250 A soft-starters where the analysis was carried out considering a current limitation of 450%, a motor operating without load and a starting regime of 10 starts per hour and the other, where only the results will be presented, involving a 13.8 kV, 600 A soft-starters where the analysis was carried out considering a current limitation of 300%, a motor operating without load and a starting regime of 3 starts per hour. Results indicate a prominent presence of the 5th harmonic. It was also shown that the number of starts does not influence the value of the harmonic content injected by the soft-starter and, consequently, it is concluded that the soft-starters tested comply with the recommendations set out in the IEEE 519:2014 standard for the configurations discussed.