FEATURE SPONSOR
GEARS FIRST MAJOR CHANGE
The first major change in kW class gears was the move towards using a planetary gear arrangement coupled to a double helical stage. The net effect of this was to reduce weight and increase torque density.
A good example of this was the reduction in weight of a straightforward helical gear used in a V44 660kW turbine from around 5.5 tonnes to 4.4 tonnes, a massive weight reduction of 20%.
TORQUE DENSITY
MAINTENANCE REGIMES Better maintenance regimes, condition monitoring/management, better oils and oil care have all played their part. Significant development by gearbox manufacturers, more powerful design software modelling, better manufacturing technology, improved materials and understanding of the turbine operating environment have all been crucial in this area. A prime example of where these factors have combined along with the prevalence of the planetary gear arrangement is the adoption of the integrated bearing within the planet wheel.
GEARBOX FAILURE
Torque density is the relationship between the weight of the gear and the torque it is capable of handling. As gear designs and materials become more efficient the torque density figure rises.
So we can see that in the relatively short time that our industry has existed turbine size and the gearboxes within these turbines have had to cope with the size increase while in real terms reducing in size themselves.
Gearboxes now exist as single planetary with two helical stages, double planetary with one helical stage and even three planetary stages. (Hybrid gearbox and generator arrangements are available too. Google Moventas Fusion Drive) Modern gearboxes are now complex and highly efficient drive train systems and there reliability in recent years has significantly improved.
A DOUBLE PLANETARY STAGE GEAR WITH A SINGLE HELICAL STAGE Reliability has always been a stone thrown at the gearbox and some of the stone throwing was certainly justified in the early days, however as the industry has grown, learned the lessons from other industries and developed itself, reliability is an ever improving area.
Bearing failure in planet wheels has been a major cause of gearbox failure in the past and still exists today where non-integrated bearings or badly designed integrated bearings are used. These failures are almost impossible to correct in the nacelle and are always costly when it comes to a factory service.
A double planetary stage gear with a single helical stage
www.windenergynetwork.co.uk
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