generators for geared and direct drives, and other
TRANSCRIPT
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Generators for geared and direct drives,
and other electrical components
Professor Robert Nilssen, Electrical power, NTNU
INT MARE WINT 2013
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Magnetic fields and currents - induce voltages in windings
- produce forces in the generator
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P M
S M
isul
il
id,mach
us
Electric energy conversion - Variable power into the stable grid
- Variable speed, variable frequency
- Need for control
AC til DC DC til AC MtE EtE EtE
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Converters more functionality but higher costs
Induction generator
– doubly fed
PM generator
– full converter
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A look at the «system»
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Norwegian wind vision
To support our oil industry??
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Very large power units offshore !!
10-12MW? 3-5??MW 6-8 MW ??
Our goal: • 12 MW • Nacelle weight 350t!!? • Generator for less
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Some experiments in the North sea
allready
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A total technology optimization is
needed
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Huge investments in infra stucture
are needed
Energy storage
How do we control power flow and handle fault situations??
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Huge investments in subsea cables
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Back to the generator technology
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Wind turbine
with gear
Gear
Shaft
Small generator
(high speed)
Transformer, power
electronics
Large torque
Low torque generator
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What are the alternatives?
With gear – not roboust
Garles - durable - expensive
Hydraulic pump
Hydraulic gear - Low top weight - New - exciting - To be verified
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Direct driven Generators
• Low speed requires synchronous machines with high pole numbers
• With high pole numbers
-Field winding in Rotor, large diamter, High cost -PM magnetization, Less cost
• Why direct drive: - gear problems above 4 MW - less maintenance
• Why not:
- High Investment costs and weight
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New technology is needed to
keep offshore wind cost down!!
Cost
Power per unit
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Modular design
Rotor
Shaft
Stator
Converter
/Transformer
Flexible mounting
Framewok/Infrastructure
•Is it smart to use modular building blocks? •Should we integrate more? •ScanWind design -3.5MW
Bearing
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Scanwind an early
Norwegian Permanent
Magnet
Direct Drive
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Synchronous PM generator
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Gearless: Less speed – higher torque – larger and more expensiv generator
07.09.2013
Large generator – increased weight
P=wT T= k D2L
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The Enercon generator - Direct drive
- Without magnets
- Good
- Expensive
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Replacing the rotor winding with
permanent magnets
High pole numbers forces the rotor to be big.
Permanent magnets make the rotor and overall stator smaller.
Rotor with windings Rotor with Permanent Magnets
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Small magnetic poles gives normally a
very large slot number
-Insulation and fill factor in the slots become a problem. -Large number of components to assemble
Slots
Magnets
– why so small??
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Expensive distributed
windings for high pole
number radial flux
machines
Unique mobility
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Concentrated and fractional slot
winding
SmartMotor Design – verified at NTNU
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Motor, Gear and generator
– PhD study at NTNU
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RFPM-machine with
plastic cover
• Machine ready for testing
• Built by a PhD student
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The switch
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More integration
Converter/
Shaft
Fixed shaft Less bearings Simple frame Enercon – design
Shaft Rotor
Shaft
Framework/Infrastructure
Stator
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This technology is here 2010
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Secret design from Siemens
Januar 2010
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More integration
Con-
verter
Trafo
Inner stator Simple frames Large diameters
Rotor
Framework/Infrastruktur
Shaft
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Expectations for new technologies
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Aksial flux generators – often called disc
machines
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AFPM
Design drawing
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Axial flux machine
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Bygget!
AFPM – Built and tested
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The Sway turbine – generator – the biggest axial
flux machine in the world – 10- 12 MW
First on the sea bed
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Composite air cooled axial
flux stator
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