VectoraLab Lab

Electric Motor Vibration Sources Mechanical Sources: • Rotor unbalance (1X dominant) • Shaft misalignment (1X + 2X) • Bearing defects (BPFO/BPFI envelope) • Mechanical looseness (many harmonics) • Resonance Electrical Sources: • Rotor bar defects: 1X sidebands at ±2sf around 1X (where s=slip, f=line frequency) • Stator eccentricity: 2× line frequency (2×LF = 100/120 Hz) • Loose stator coils: 2×LF harmonics • Air-gap eccentricity: poles × shaft frequency sidebands Motor Specific Frequencies: • Line frequency: 50 Hz (EU) / 60 Hz (US) • 2 × Line: 100 / 120 Hz • Pole pass frequency: poles × slip frequency • Rotor bar pass: #bars × f_rotor Measurement Tips for Motors: • Measure H, V, Axial at both DE and NDE bearings • Compare DE vs NDE for unbalance/misalignment evidence • Check 2×LF magnitude for electrical issues • Use MCSA (Motor Current Signature Analysis) alongside vibration Important: Electrical and mechanical faults can produce similar vibration patterns. Always confirm electrical faults with MCSA before blaming mechanical causes.