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Critical speed is the rotational speed at which a rotating shaft reaches natural frequency resonance. Operating above or below critical speed is essential.

Formel

Calculate: N_crit = (60 × √(g × δ)) / (π × √(W/g))
W
W value — Variable used in the calculation

Trinn-for-trinn guide

  1. 1Calculate: N_crit = (60 × √(g × δ)) / (π × √(W/g))
  2. 2Or use stiffness and inertia: ω_n = √(k/I)
  3. 3Operating speed should be <70% or >130% of critical

Løste eksempler

Inndata
Shaft natural frequency 3000 rpm
Resultat
Operating range <2100 rpm or >3900 rpm safe
Avoid 2100-3900 band

Vanlige feil å unngå

  • Operating continuously near critical speed
  • Under-estimating critical speed (causes resonance)

Ofte stilte spørsmål

What happens at critical speed?

Resonance causes excessive vibration, noise, and potential failure from fatigue.

Can you operate near critical speed briefly?

Yes, passing through critical speed quickly during startup/shutdown is acceptable.

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