Industrial Engineer · phase 11 of 16 · noun
Open-Loop Control
Motor control without direct shaft-speed or position feedback from an encoder.
The Explain card
- Plain English
- Open loop means the drive commands a frequency and trusts the motor to follow. There is no encoder telling it what the shaft is actually doing.
- Example
- A fan drive is told 45 hertz and applies 45 hertz. If the belt slips or the load changes, the drive never knows, and the fan simply runs at whatever speed results.
- Why it matters
- Open loop is cheaper, simpler and good enough for most fans, pumps and conveyors, where a few percent of speed error is fine. It is the wrong choice where speed must be exact, where full torque is needed at zero speed, or where the load can drive the motor.
- Hook
- Command the speed and hope.
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 selects Open-Loop Control and checks motor current while stepping the frequency reference.
Why these words
- open Old English open, not closed modifies loop to classify its signal-path structure
- loop Middle English loupe, a fold or bend names the circuit or path considered by the control scheme
- control Anglo-French contreroller, to check against a register serves as the head noun naming the engineering function
Where it came from
- Origin
- English control-engineering compound formed from open, loop, and control
- Entered the language
- 1940s
- What changed
- The ordinary words were specialized in feedback theory and later adopted in industrial drive terminology.
How it is spelled
- Pattern
- Open-loop is hyphenated because the two words jointly modify control.
- Pattern
- Both parts of open-loop retain their standard spellings.
Spelled like
- closed-loop
- single-loop
- multi-loop
Broken into chunks
-
open
- opening
- reopen
-
loop
- looped
- looping
-
control
- controller
- controllable
What it sits beside
Same subject
- closed-loop control
- frequency reference
- volts-per-hertz control
- sensorless vector control
Same shape
- closed-loop control
- open-loop gain
- open-loop response
control architectures
- open-loop control
- closed-loop control
VFD control modes
- volts-per-hertz control
- sensorless vector control
- closed-loop vector control
Where it sits in the deck
Phase 11: VFD Control Modes and Tuning
How a drive decides what to send the motor, from plain volts per hertz up to closed loop vector control, and how each mode is tuned.
