synchronous speed
C1/C2Specialist/Technical
Definition
Meaning
In electrical engineering, the constant speed at which the rotating magnetic field of an AC motor's stator rotates; the theoretical speed a motor would achieve if there were no slip between the rotor and the magnetic field.
Also used to describe any coordinated speed where multiple systems or components operate in perfect temporal alignment, such as in data transmission, computing, or mechanical systems where precise timing is required.
Linguistics
Semantic Notes
The term is almost exclusively technical. In its core sense, it is a precise measurement (in revolutions per minute - RPM) determined by the power supply frequency and the motor's pole count. It describes a theoretical state; actual rotor speed is always slightly less (asynchronous) due to slip.
Dialectal Variation
British vs American Usage
Differences
No significant difference in meaning or usage. Spelling conventions follow the usual patterns (e.g., 'synchronous' vs. 'synchronized' in other contexts).
Connotations
Identical technical connotations in both dialects.
Frequency
Equally low-frequency and confined to engineering and technical contexts in both regions.
Vocabulary
Collocations
Grammar
Valency Patterns
The [motor/generator] operates at/above/below synchronous speed.Synchronous speed is determined by [frequency] and [number of poles].To calculate the synchronous speed, use the formula Ns = (120f)/P.Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Rare. Might appear in procurement, technical specifications, or project management documents for industrial equipment.
Academic
Common in electrical engineering, physics, and mechanical engineering textbooks, lectures, and research papers on motor design and power systems.
Everyday
Virtually never used.
Technical
The primary context. Found in motor datasheets, control system manuals, technical discussions about induction vs. synchronous motors, and power generation.
Examples
By Part of Speech
adjective
British English
- The synchronous-speed operation is only theoretical for this type of motor.
American English
- The synchronous-speed calculation is fundamental to motor design.
Examples
By CEFR Level
- For a motor connected to a 50Hz supply, the synchronous speed is 3000 RPM if it has two poles.
- The generator cannot maintain a stable output if it deviates from its synchronous speed.
- Engineers must ensure that the turbine's rotational speed is precisely matched to the grid's synchronous speed to enable seamless connection.
- The phenomenon of 'hunting' occurs when a synchronous motor oscillates around its equilibrium synchronous speed due to sudden load changes.
Learning
Memory Aids
Mnemonic
Think of a clock's hands moving perfectly together: they are SYNCHRONous. In a motor, SYNCHRONous SPEED is when the rotor would perfectly keep up with the invisible rotating magnetic 'hand' (field).
Conceptual Metaphor
A DANCING PARTNER: The stator's magnetic field is the lead dancer moving at a fixed tempo (synchronous speed). The rotor (the follower) tries to match the step perfectly but always lags a tiny bit (slip) unless it is a special synchronous motor.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid direct translation traps like *'синхронная быстрота'*. The correct technical term is 'синхронная скорость'.
- Do not confuse with 'синхронизированная скорость' (synchronized speed), which implies an active process of matching speeds, while 'synchronous speed' is a fixed, inherent property of the system.
Common Mistakes
- Using 'synchronous speed' to describe two separate things moving at the same speed (use 'synchronized speed').
- Pronouncing 'synchronous' as /saɪnˈkrɒnəs/ instead of /ˈsɪŋkrənəs/.
- Thinking actual motors (especially induction motors) run at synchronous speed; they run slightly slower.
Practice
Quiz
What primarily determines the synchronous speed of an AC motor?
FAQ
Frequently Asked Questions
No, induction motors run at a speed slightly less than synchronous speed. This difference is called 'slip' and is essential for the motor to produce torque.
Ns (in RPM) = (120 * f) / P, where 'f' is the supply frequency in Hertz, and 'P' is the number of poles in the motor.
It is a core term in electrical engineering, specifically in the fields of electric motors, generators, and power systems.
No. 'Synchronous speed' is a fixed, inherent property of an AC motor based on its design and power supply. 'Synchronized speed' refers to the act of adjusting two or more independent systems to run at the same speed.