Rotor imbalance of wind turbines: Detection and Adjustment

Optimum operation of wind turbines: correct rotor adjustment and balancing

A major cause of the dynamic problems found in wind turbines today is rotor imbalance.
On routine inspections (inspections without special cause), approximately 81 percent of wind turbines exceed their design limits for rotor imbalance.

Rotor imbalances may have different causes:

  • Uneven distribution of rotor mass (mass imbalance)
  • Deviations in the aerodynamic properties of the blades, such as blade angle deviations between the individual blades (aerodynamic imbalance).

The individual blade angles of the three blades are examined in order to identify and quantify relative deviations as this has an impact on both energy production and lifespan.

Our experience has shown that relative blade angle differences of more than 0.3° lead to significant aerodynamic imbalance.

Additionally, significant deviation of the blade from its designed angle negatively impacts energy production.

The measuring system we use is the Plug-and-Use Balancing Box. It checks the wind turbines for rotor imbalance through vibration measurements. Individual measuring conditions are specified for each wind turbine type and configuration in order to assure comparable measurement results. The on-site evaluation of the measurements includes a comparison of the measured vibration level with specified limit values. 

If an improper rotor imbalance is detected, we recommend  a more extensive measurement to correct the root cause.

To ensure high quality results, we measure the blade angles using a well-proven photo-optical method and appropriate statistical analysis.

Our services:

  • Rotor balancing
  • Vibration measurements
  • Blade angle measurements
  • Onsite evaluations
  • Root cause analyses