Industrial Engineer · phase 10 of 16 · noun
Synchronous Speed
Rotating magnetic-field speed determined by applied frequency and motor pole count, equal to 120 times hertz divided by poles in rpm.
The Explain card
- Plain English
- Synchronous speed is how fast the magnetic field rotates inside the motor. It depends only on the applied frequency and the number of poles, and it is 120 times the frequency divided by the pole count, in rpm.
- Example
- A four pole motor at 60 hertz has a synchronous speed of 1800 rpm. At 30 hertz it is 900. A two pole motor at 60 hertz is 3600.
- Why it matters
- An induction motor always turns a little slower than synchronous, and a synchronous motor turns at exactly this speed. The formula is how you check a drive's frequency against a tachometer and how you size a gearbox.
- Hook
- The speed of the field, before the load has its say.
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 compares the induction motor's measured shaft rpm with its Synchronous Speed to calculate slip.
Why these words
- synchronous Greek synkhronos, occurring at the same time modifies speed by linking it to coordinated timing
- speed Old English sped, success or rapid movement serves as the head noun naming the rotational quantity
Where it came from
- Origin
- English engineering compound built from synchronous and speed, with synchronous derived from Greek syn, together, and khronos, time
- Entered the language
- 1890s
- What changed
- Synchronous moved from general simultaneity to coordinated machine timing, while speed developed from success and rapid progress to a measurable rate.
How it is spelled
- Pattern
- The syn- prefix keeps its n before the ch spelling.
- Pattern
- The ch represents the k sound found in Greek-derived words.
- Pattern
- The adjective ending -ous is retained before the noun.
- Breaks the pattern
- The first y in synchronous represents a short i sound rather than the consonant sound heard in yes.
Spelled like
- synchronize
- synchronism
- chronology
- chronometer
Broken into chunks
-
syn
- synthesis
- synergy
-
chron
- chronology
- chronometer
-
ous
- continuous
- inductivous
-
speed
- speedometer
- speedway
What it sits beside
Same subject
- rotor speed
- slip
- pole count
- line frequency
- induction motor
Same shape
- synchronous motor
- synchronous generator
- synchronous operation
motor speed terms
- Synchronous Speed
- rotor speed
- base speed
- maximum speed
synchronism terms
- synchronous motor
- synchronous generator
- synchronous condenser
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.
