محاسبه‌ی فرکانس هارمونیک

Simply divide RPM by 60:

Hz = RPM / 60

For example: 3000 RPM / 60 = 50 Hz. This gives the fundamental (1×) rotational frequency.

Harmonics are integer multiples of the fundamental (1×) frequency:

• 1× = fundamental = one event per revolution
• 2× = second harmonic = two events per revolution
• 3× = third harmonic = three events per revolution

Different faults produce characteristic harmonic patterns. Unbalance is primarily 1×, misalignment shows strong 2× and sometimes 3×, and blade pass frequency is number-of-blades × 1×.

The 1× frequency (one-per-revolution) is the most fundamental vibration component. Common 1× sources:

• Mass unbalance — the most common source
• Bent shaft — creates 1× with axial component
• Eccentric rotor — electrical machines
• Resonance — if natural frequency coincides with 1×

1× vibration phase is crucial for balancing — it tells you the heavy spot direction.

Higher harmonics reveal specific mechanical faults:

• 2×: Misalignment (angular and parallel), looseness, cracked shaft
• 3× and above: Severe misalignment, mechanical looseness
• Blade pass (N×): Impeller/fan blade problems
• Gear mesh (Z×): Gear tooth problems

The ratio of harmonic amplitudes to 1× amplitude is a key diagnostic indicator.

Hz (Hertz) = cycles per second. Absolute frequency unit.

CPM (Cycles Per Minute) = Hz × 60. Numerically equal to RPM for 1× order.

Orders (1×, 2×, ...) = multiples of shaft speed. Speed-normalized — they stay the same regardless of RPM.

Example at 3000 RPM: 1× = 50 Hz = 3000 CPM; 2× = 100 Hz = 6000 CPM.