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כיצד לחשב את Critical Speed

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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.

נוסחה

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

מדריך שלב אחר שלב

  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

Worked Examples

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

Common Mistakes to Avoid

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

Frequently Asked Questions

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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