Benshaw Soft Starters and Harmonics
This Benshaw factsheet explains the relationship between soft starters and harmonics in motor control applications. It details how SCR-based soft starters function, how harmonics are generated, and why Benshaw designs minimize distortion and comply with harmonic standards.
Key Points
- Harmonics are multiples of the fundamental frequency and result from non-linear electrical loads.
- Benshaw soft starters use back-to-back SCRs for symmetrical switching, effectively eliminating even-order harmonics.
- Benshaw products comply with IEC60947-4-2 standards for electromagnetic compatibility and maintain harmonic levels well below IEEE 519 guidelines.
- Continuous harmonic production only occurs in soft starters with active “energy saving” features—not in Benshaw designs.
- Soft starters generate harmonics only during motor starting and stopping, unlike variable speed drives (VSDs) which produce them continuously.
- Total harmonic distortion (THD) rapidly decreases during startup and becomes negligible once the bypass contactor engages.
- The short duration and low magnitude of harmonic generation make soft starters a non-issue in most installations.
- Benshaw offers robust technical support and a full product range for industrial motor control.