Star Delta Starters: How does soft start compare with star/delta starting?

Compared with star/delta starters, soft starters are much more flexible and provide a smooth start with no risk of transients.

Star/delta starters offer limited performance because:

• start torque cannot be adjusted to accommodate motor and load characteristics.
• there is an open transition between star and delta connection that results in damaging torque and current transients.
• they cannot accommodate varying load conditions (eg loaded or unloaded starts).
• they do not provide soft stop.

The main advantages of star/delta starters are:

• they may be cheaper than a soft starter.
• when used to start an extremely light load, they may limit the start current to a lower level than a soft starter. However, severe current and torque transients may still occur.