Induction Motor Starting
DOL, star-delta, autotransformer and soft starters limit the high starting current.
Intermediate
A motor started direct-on-line draws 5–8× rated current.
| Method | Starting current | Starting torque |
|---|---|---|
| Direct-on-line (DOL) | 100 % (≈ 6× FLC) | 100 % |
| Star–delta | ⅓ of DOL | ⅓ of DOL |
| Autotransformer (tap ) | of DOL | of DOL |
| Soft starter | adjustable | reduced, smooth ramp |
| VFD | ≈ rated current | full torque, any speed |
Star-delta starters are common in India for motors of a few kW and above; VFDs are increasingly preferred because they also save energy on pumps and fans.
Spotted a mistake or want to add detail? Suggest an improvement — Content Contributors' edits are reviewed by editors before they go live.
Discussion (0)
Sign in or join free to ask questions and discuss this topic.