Transcript The Effect of Gearbox Architecture on Wind Turbine

The Effect of Gearbox Architecture on
Wind Turbine Enclosure Size
Charles D. Schultz, PE
Beyta Gear Service
Winfield, Illinois
What was the objective of this paper?
• Demonstrate the “scaleability” of gear design
• Examine alternate designs for wind turbine
gearboxes
• Begin a discussion of how design decisions
effect overall system size
Typical Wind Turbine
Complete Gear Set
“3PPH” arrangement
What was the scope of this work?
• Theoretical work only –not connected to
any past, present, or future project
• Design conditions are relevant but
simplified
• Work limited to gears only
Design Condition Summary
• In place of a Miners’ Rule load spectrum a 1.5
application factor was used
• 2mW nominal capacity
• Gears rated for 85,000 hours of full load life
[approximately 10 years of 24/7 operation]
• 15 rpm rotor speed
• 7 different output speeds
• 4 different gear arrangements per output speed
Key Design Decisions
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Pinion tooth counts
Number of planets
Allowable face width/pitch diameter ratio
No divided power path arrangements due
to radial timing concerns
• All external gearing is carburized,
hardened, and ground
Gear Arrangements Considered
• All external gears
• Multiple planetary stages
• Single planetary stage with multiple
external stages
Design Procedure Used
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Establish set geometry at 1 NDP
18 tooth minimum
1.3 minimum Mp
1.0 minimum Mf
1.25 maximum face width/pinion pitch
diameter ratio
• Run ratings for 1 NDP gearsets
Design Procedure Used
• Calculate NDP needed to achieve required
capacity
• Draw cross section of gear train
• Approximate size of related rotating parts
• Calculate weights and volumes
• Compare results for different designs
Scaleability Example
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1 DP gear set
18 x 18 sun/planet
12° Helix
20° NDP
1.25 FW/D ratio
(3) planets
2.7 mesh factor
• Durability limited
• 2372.47 hp x 2.7 =
6405.669 hp
• (6405.669/4023
RDC)^.333 = 1.1677
• Rating for 1.1677 NDP =
1494.42 x 2.7 = 4034.934
HP
• 4034.934/4023 = 1.003
• .3% “error” is due to
dynamic factor changing
Arrangements to the same scale
Effect of increasing number of
planets
• Figure 1 shows the relationship between
the stage ratio and the maximum number
of planets
• Figure 2 shows the dramatic effect of
increasing the number of planets
• Load sharing becomes a concern as the
number of planets is increased
Number of planets vs. ratio
Envelope vs # planets
Results
• The planetary arrangements currently in use are a
logical choice based upon minimum enclosed volume,
lowest weight, and relative cost to manufacture
• Other arrangements may have potential advantages in
terms of serviceability and packaging
• For total ratios of over 40:1 a two planetary stage/one
helical stage arrangement gives the best results
• Total gear ratio seems to have little effect on GEARBOX
cost in the 60:1 to 120:1 ratio range
Suggestions for Further Work
• How is generator size effected by output rpm?
• How do “flex pin” arrangements effect the choice
of number of planets and overall cost?
• Can designs be developed to permit “up tower”
rebuildability?
Thank You:
• Noel Davis of Vela Gear Systems
• Mark Haller of Haller Wind Consulting
• Octave LaBath of Cincinnati Gear
Consulting
• Amy Lane of AGMA
• Peer Review Team of AGMA