Industrial Engineer · phase 8 of 16
VFD
Variable Frequency Drive, an electronic motor controller that varies output frequency and voltage to control AC motor operation.
The Explain card
- Plain English
- A VFD takes fixed frequency power from the wall and makes new power at whatever frequency and voltage the motor should see. Change the frequency and an AC motor changes speed.
- Example
- A 60 hertz fan motor runs flat out across the line. Behind a drive it runs at 30 hertz for half speed and draws roughly an eighth of the power, because fan power falls with the cube of speed.
- Why it matters
- Drives are the single biggest energy saving in most plants and the single biggest source of electrical noise. They also soft start motors, protect them, and report on them, so a modern motor circuit almost always has one.
- Hook
- Rectify it, store it, chop it back out at the speed you want.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During commissioning, the technician enters the motor nameplate data in the VFD and verifies rotation before coupling the pump.
Letter by letter
- V Variable indicates that an operating quantity can change
- F Frequency names the electrical quantity represented by hertz
- D Drive identifies the motor-control equipment class
Where it came from
- Origin
- English initialism formed from the initial letters of variable frequency drive
- Entered the language
- 1960s
- What changed
- The full technical phrase was shortened as solid-state industrial drive systems became more common.
How it is spelled
- Capitalisation
- Written VFD in capitals, including mid-sentence
- Plural and possessive
- The plural is VFDs, the singular possessive is VFD's, and the plural possessive is VFDs'.
- Out loud
- Spelled out letter by letter.
Same family
- PLC
- HMI
- MCC
Broken into chunks
-
VF
- V/f control
- variable-frequency control
-
D
- AC drive
- motor drive
What it sits beside
Same subject
- induction motor
- DC bus
- braking resistor
- motor nameplate
Same shape
- PID
- RTU
- UPS
industrial motor controllers
- VFD
- soft starter
three-letter controls initialisms
Where it sits in the deck
Phase 8: VFD Drive Hardware and Power Path
Inside the drive: rectifier, DC bus and inverter, the three stages every variable frequency drive uses to rebuild the waveform a motor sees.
