Machine Diagnostics Electrical and mechanical analysis

Analysing your technical equipment and plant gives you information that you can use to increase service lifetimes and avoid expensive downtime and repair costs. We provide support in the following types of analysis:

Electrical analysis

  • Winding resistance, insulation resistance, polarisation index (PI)
  • Shock pulse measurement
  • PD measurement
  • System analysis

Mechanical analysis

  • Bearing diagnosis
  • Frequency analysis
  • Natural frequency determination
  • Modal analysis
  • Acoustic analysis
  • Campbell diagrams

VEM prepares and evaluates vibration analyses that include the general working environment of your equipment and plant alongside your drives and generators.

Bearing diagnosis

Damage to rolling bearings often causes undesired machine downtime; analysing bearing condition involves frequency analysis using FFT and envelope curve methods. As an example, we prepare a bearing "fingerprint" upon commissioning on site and compare the results with the results taken before delivery to identify transport damage.

Spectrum with bearing failure indicated by an outer race frequency peak at 128 Hz

Frequency analysis

Frequency analysis refers to electrical, mechanical and acoustic parameters, providing a universal way of gaining insights into interference composition for root-cause analysis. We provide frequency analyses (FFT and CPB) in stationary operation as well as non-stationary processes, such as rolling mill drives powered by converters.

Peaks of rotating frequency with harmonics of an 8 MW cement mill drive at 1200 rpm

Natural frequency determination

Excessive vibration often causes damage to plant and equipment, and is mostly caused by combining excitation and natural frequencies in what is referred to as resonance. We determine natural frequencies in machine components by simple experiments involving striking the component and interpreting the response.

Decay of vibration amplitudes after impact test with eigenfrequency peaks

Modal analysis

Modal analysis provides additional information on natural frequencies; apart from natural frequencies, this allows normal mode and damping parameter determination by experimentation. We store the experimental modal parameters in numerical form for calculating specific countermeasures. We also recommend any necessary changes to your plant or equipment as required.

R3-Mode of 18 MW propeller motor stator core at 103 Hz

Acoustic analysis

Sound and its composition play an important role in machine diagnostics, for example in clearly distinguishing sounds caused by a converter from those caused by a damaged bearing with current passing through. Apart from qualitative analysis, we provide quantitative analysis for determining sound power or tonality, such as in wind turbines.

Sound intensity of wind power generator showing mechanical and magnetical contributions

Campbell diagrams

Campbell diagrams are a major tool in diagnosing vibration conditions, while also visualising excitation orders and natural frequencies in a diagram for determining excitation such as due to imbalance, misalignment, tooth engagement or coupling bolts, or natural frequencies such as natural bending frequencies and base natural frequencies, and how they interact and resonate. Parameters used include amplitude, speed, acceleration, noise pressure and electrical parameters.

Campbell Diagram of a traction motor up to 6000 rpm showing resonance at 4000 rpm