Industrial Engineer · phase 10 of 16
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.
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.
