Industrial Engineer · phase 12 of 16 · noun
Two-Wire Control
Maintained-contact control scheme in which the run input remains asserted while operation is requested.
The Explain card
- Plain English
- Two wire control uses a maintained contact for run. Close it and the drive runs, open it and the drive stops, and the contact state is the command.
- Example
- A selector switch on the panel closes the run input and stays closed. The drive runs until someone turns the switch back.
- Why it matters
- Two wire is simple and it restarts the motor automatically when power returns with the switch still closed, which is either a feature or a hazard depending on the machine. Fans and pumps often want it, machines near people usually do not.
- Hook
- The switch is the command, for as long as it is closed.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During VFD commissioning, the technician selected Two-Wire Control, checked the restart setting, and tested the hardwired stop circuit at the motor control center.
Why these words
- two Old English twā and twegen, from Proto-Germanic twai specifies the number associated with the wiring arrangement
- wire Old English wīr, metal thread identifies the electrical connection medium
- control Middle French contrôle, from contrerole, a counter-register names the operational function of the phrase
Where it came from
- Origin
- English technical compound formed from two, wire, and control
- Entered the language
- 20th century
- What changed
- The ordinary words for number, conductor, and regulation became a standardized motor-control label contrasted with three-wire control.
How it is spelled
- Pattern
- The number-plus-noun unit two-wire is hyphenated before control.
- Pattern
- The number is conventionally spelled out rather than written as 2.
Spelled like
- three-wire control
- two-speed motor
- four-wire transmitter
Broken into chunks
-
two
- twice
- twin
-
wire
- wired
- wiring
-
control
- controller
- controlling
What it sits beside
Same subject
- three-wire control
- motor starter
- seal-in circuit
- digital input
- variable frequency drive
Same shape
- three-wire control
- four-wire measurement
- two-speed control
motor control schemes
- two-wire control
- three-wire control
VFD digital input commands
- run forward
- jog
- fault reset
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.
