Primary Resistance Starters: How does soft start compare to primary resistance starting? 

Compared with primary resistence starters, soft starters are more flexible and reliable.
Primary resistance starters offer limited performance because:
- start torque cannot be fine-tuned to match motor and load characteristics.
- current and torque transients occur at each voltage step.
- they are large and expensive.
- liquid resistance versions require frequent maintenance.
- start performance changes as the resistance heats up. So multiple or restart situation are not well controlled.
- unable to accommodate changing load conditions. e.g. loaded or unloaded starts.
- they cannot provide soft stop.