Balancing

SOURCES OF VIBRATION AND OTHER NEGATIVE PHENOMENON

During the operation even the properly functioning Wind Turbine generates the spectrum of mechanical, electromagnetic and acoustic oscillations:

- Mechanical noise of components. Appears mostly in horizontal axis wind turbines (propellers) as the result of operation of gearbox and bearings. SRC-Vertical wind turbines contain low speed axial gap permanent magnet alternator without gearbox. The only component which makes noise, is bearing;
- Aerodynamic noise. Appears due to the pressure and friction of wind flow on the turbine components, mostly blades and traverses. Each blade and traverse is loaded by alternating sign aerodynamic loading which may cause mechanical noise;
- Aerodynamic ultrasound. It can be generated by small or thin elements of turbine such as wire guys, traverses, bolts, fragments of dry insect bodies, etc.;
- Electromagnetic oscillations. Appear due to the rotation of alternator windings in magnetic field and generating electrical moving force in windings;
- Aerodynamic infrasound. Appears due to the burble on the blades and turbulence of the wind flow behind the turbine. Vertical axis turbines do not have this phenomenon due to rotor configuration;
- Mechanical infrasound. Being generated while appearing harmonics during the rotation of the hub due to not ideal quality of friction surfaces, defects and disbalances;
- Vibrations. Appear during the operation of wind turbine due to the external forces, internal influence of components on each other, disbalance of rotating parts, bending forces of blades and mast, interaction of magnets and winding inside alternator. The vibration may cause infasound and noise. Resonance will be generated if some of the harmonics of external force or torque will be equal to the self oscillations (or harmonic) of the turbine component(s).The analysis of wind turbine parameters negatively influencing on the environment and human health, leads to the conclusion that the main source of negative processes is the vibration geneated during the turbine operation as the result of ineracting of many physical processes.
The main task of reduction of influence of negative parameters on the environment is the reduction of vibration up to the level determined by standards and norms. This task is solved with the help of method developed at SRC-Vertical, Ltd. (Eugene Solomin). Alternator vibrations are not taken into account in this method because they should be reduced by special approach also used at SRC-Vertical.

The rest parameters of wind turbine should be measured and adjusted in accordance with applicable standards during research and design stage if needed.

Parameters of Wind Turbine standardized by applicablestandards and norms (shown as average and acceptable for most countries):

METHOD OF REDUCTION OF VIBRATION OSCILLATIONS:

Method of reduction of dangerous and harmful influence generated by Wind Turbine during the operation, can be divided on to two theoretical and one experimental procedures with further analysis of parameters on the requirements of applicable standards and norms.

METHOD OF THEORETICAL CALCULATIONS AND CORRECTION OF DESIGN DOCUMENTATION:

Calculation of force factors and mode of deformation of turbine components is made in NASTRAN programming complex:
   
Use VisSim visual simulating software for calculating resonances with self oscillations of turbine taking into account the following external force loading (on the base of data calculated during the research of the 3D computer model in NASTRAN complex):
- aerodynamic forces acting on the rotor;
- aerodynamic torques acting on the rotor;
- periodical inertia torques caused by non-zero centrifugal inertia torques;
- periodical inertia forces caused by displacement of rotor mass center from rotation axis.

 
 
Get the functional dependences of forces and torques acting on the turbine during operation on the base of mathemetic model of Wind Turbine (the sample of disturbing forces with prognosed resonances):
 
 
Determine the forms and modes of self oscillations of rotor:



Calculate the horizontal and vertical vibromotion of components (the sample):

 

Non-harmonic oscillation to be distributed into Fourier row (the sample):

 

Make tables of prognosed resonances for design assembly on all frequences of rotor rotation (on the base of analysis of spectrums):


 
Calculate the vibromotion of mast which causes the pressure on the base:

 

Deep analysis of all calculated data leads to the correction of design documentation.

METHOD OF PRACTICAL WEIGHT BALANCING OF ROTOR:

After research and design stage and prototype fabrication, rotor has to be balanced in accordance with the developed method using provocative weight:

 

Vibration balancing using the specially designed and pre-programmed vibro-analyser allows reducing the vibration of SRC-Vertical Wind Turbine rotor 100 times below the limits required by applicable standards and norms:
 
The scientists of SRC-Vertical continue working on reducing the vibrations generated by mechanical and electrical forces.