Industrial Engineer · phase 10 of 16
PWM
Pulse-Width Modulation, an inverter switching method that controls effective motor voltage and frequency by varying pulse timing.
The Explain card
- Plain English
- Pulse width modulation is how the inverter makes a variable voltage out of a fixed DC bus. It switches the bus on and off very quickly, and the width of each pulse sets the average voltage the motor feels.
- Example
- To make a sine wave, the drive sends wide pulses near the peak and narrow pulses near the zero crossing. The motor's inductance smooths the pulses into a nearly sinusoidal current.
- Why it matters
- PWM is why a drive is efficient and why its output is a train of sharp edges rather than a clean sine. Those edges are the source of reflected waves, bearing currents and the whine you hear from the motor.
- Hook
- Fast on and off, averaged into whatever voltage you asked for.
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 measured the PWM output waveform at the motor terminals and checked its carrier frequency.
Letter by letter
- P Pulse a brief electrical switching event
- W Width the duration of each pulse
- M Modulation systematic variation of a signal characteristic
Where it came from
- Origin
- English technical coinage formed from pulse, width, and modulation
- Entered the language
- mid-20th century
- What changed
- The expression moved from communications and control terminology into power electronics, motor drives, and embedded control.
How it is spelled
- Capitalisation
- Written PWM in uppercase, even mid-sentence; the expanded form is usually written pulse-width modulation.
- Plural and possessive
- Use PWMs for multiple PWM systems or signals, PWM's for the singular possessive, and PWMs' for the plural possessive.
- Out loud
- Spelled out letter by letter.
Same family
- VFD
- IGBT
- SVPWM
- SPWM
Broken into chunks
-
pulse-width
- pulse-width control
- pulse-width encoding
-
modulation
- frequency modulation
- amplitude modulation
What it sits beside
Same subject
- carrier frequency
- duty cycle
- DC bus
- inverter
- IGBT
Same shape
- PFM
- PAM
- PCM
modulation initialisms
- PWM
- PFM
- PAM
- PCM
drive switching methods
- SPWM
- SVPWM
Where it sits in the deck
Phase 10: VFD Electrical and Motor Fundamentals
The physics under the parameters: slip, torque, flux, and the relationship between frequency and voltage that every drive is really controlling.
