Industrial Engineer · phase 16 of 16
Soft Starter
Solid-state starter that limits motor starting voltage and current but does not provide continuous variable-frequency speed control.
The Explain card
- Plain English
- A soft starter ramps the voltage to a motor up gently at start using thyristors, then usually bypasses itself with a contactor. It limits inrush and mechanical shock and does nothing about speed once the motor is running.
- Example
- A 200 horsepower compressor starts on a soft starter to keep the line from sagging. Once up to speed it runs across the line at full speed, and the soft starter's work is done.
- Why it matters
- A soft starter is cheaper and simpler than a drive when the application only needs a gentle start and never needs speed control. Choosing one when the load would benefit from variable speed gives up the energy saving that would have paid for the drive.
- Hook
- A gentle start, then out of the way.
Where it sits in the deck
Phase 16: VFD Related Drive Terms
The drive family's wider vocabulary, from soft starters and servo drives to the regenerative units people also call a drive.
