Industrial Engineer · phase 12 of 16 · noun
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.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
The technician configured Three-Wire Control and landed the start and stop pushbutton signals on the drive's digital inputs.
Why these words
- three Old English þrīe, from Proto-Germanic þrīz supplies the numeral used in the wiring convention's name
- wire Old English wīr, metal thread places the phrase in the language of electrical circuits
- control Anglo-French contrerolle, a duplicate register used for checking identifies the phrase as the name of an operating method
Where it came from
- Origin
- English technical compound formed from three, wire, and control
- Entered the language
- 20th century
- What changed
- Control shifted from checking records to directing machinery, while three-wire became a conventional electrical modifier.
How it is spelled
- Pattern
- Three-wire is hyphenated because the compound modifies control.
- Pattern
- Three and wire retain their ordinary spellings inside the compound.
Spelled like
- two-wire control
- three-phase motor
- four-wire circuit
Broken into chunks
-
three
- three-phase
- three-pole
-
wire
- wiring
- wireway
-
control
- controller
- controllable
What it sits beside
Same subject
- start pushbutton
- stop pushbutton
- digital input
- motor starter
- variable frequency drive
Same shape
- two-wire control
- three-phase power
- three-pole contactor
control wiring schemes
- two-wire control
- three-wire control
motor-control devices
- contactor
- variable frequency drive
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.
