Industrial Engineer · phase 12 of 16
Three-Wire Control
Momentary start and stop control scheme with drive logic that seals in the run state.
The Explain card
- Plain English
- Three wire control uses a momentary start button and a momentary stop button. The drive seals in the run state itself after a start pulse and drops it on a stop pulse.
- Example
- A pushbutton station with a green start and a red stop. Tap start and the motor runs, tap stop and it stops, and after a power loss it stays stopped until start is pressed again.
- Why it matters
- The drive does the seal in that a relay circuit used to, so no restart happens on power return. Three wire is the usual choice for any machine an operator stands beside, and the stop input is normally closed so a broken wire also stops it.
- Hook
- Start is a request, stop is a demand, and the drive remembers.
Where it sits in the deck
Phase 12: VFD Commands, References, and Stopping
Starting, referencing and stopping, including the several very different things a drive can mean by the word stop.
