Sunday, December 2, 2012

Notes - Glossary

The following notes are taken from Wind Turbine Technology by Ahmad Hemami.

A
  • Abrasion - Wear in machinery between components grinding against each other
  • Active yaw - Having controlled yaw motion rather than forced motion through wind
  • Aerodynamic Force - Force exerted by moving air or gas
  • Airfoil - Profile of the outline of an airplane wing, usually having large lift coefficient and a small drag coefficient
  • Alignment - Having the axes in a straight line
  • AC - Alternating Current, type of electricity with continuously alternating direction
  • Alternator - machine generating AC electricity
  • Amplitude - instantaneous value of cyclic variable
  • Anemometer - windspeed measuring device
  • Angular speed - rotational speed of an object in radians/sec or degrees/sec
  • ANSI - American National Standards Institute
  • Arc Flash - flow of electricity outside a conductor caused by a short circuit, generates high pressure and temperature in the air
  • Arm - Part of a planetary gear that holds the planet gears together
  • Armature - Rotating part in a motor, composed of one or more windings
  • ASME - American Society of Mechanical Engineers
  • Asynchronous Generator - aka induction generator
  • Autotransformer - transformer where primary and secondary windings are part of the same winding, not isolated
  • AWEA - American Wind Energy Association
B
  • Backlash - free motion between two meshing gears due to noncontact free space between teeth
  • Balanced Load - When three loads in a three-phase electrical system have equal values
  • Bedplate - A main structure in a nacelle where all the components are mounted or attached
  • Betz Limit - Maximum value of a wind turbine's power coefficient. 16/27 or 0.59
  • Bevel Gear - Gears with perpendicular axes
  • Blade Pitch Control - The capability of turning a turbine blade about its axis with respect to its hub
  • Blade Root - attachement of blade to hub
  • Blade Tip - free end tip of blade
  • Bridge Rectifier - full rectifier where two sets of diodes alternatively conduct, converts AC to DC
  • Brush - part of carbon in an electric machine that slides on a conductor to allow for electricity transfer between moving components to stationary components
C
  • Cable Grip - Metallic device for turbine climbing
  • Capacitive Reactance - Apparent resistance due to a capacitor
  • Carabiner - Metallic device allowing connection of two rings in climbing equipment
  • Carrier - Part of a planetary gear holding gears together called arm
  • Cavitation - An interaction between metallic rotating piece and a liquid in a gearbox or pump causing erosion
  • Centrifugal force - Outward force due to rotating reference frame
  • Characteristic Curve - Curve exhibiting the main features of a device machine or equipment based on a major parameter
  • Characteristic Diagram - aka Characteristic Curve
  • Chord - Distance between leading and trailing edge of airfoil
  • Chord Line - line connecting leading and trailing edge of an airfoil
  • Collector - Point where turbine outputs in a windfarm are connected before being sent to grid
  • Compound Interest - Periodically increased interest
  • Cone Angle - angle that blades of a wind turbine make with plane perpendicular to axis of rotation
  • Corrective Maintenance - fix components after it breaks rather than preventative
  • Cost of Capital - Money spend to generate capital for investment
  • Crowbar - Set of resistors that come into operation when generator disconnects and load vanishes, prevents overspeed
  • Current - Intensity of flow of electrons in Amperes
  • Line Current - Current in supply lines of three-phase electrical system
  • Current Direction - Direction of electrons in a current
  • Cut-in Speed - minimum speed for a turbine to generate power
  • Cut-out Speed - maximum speed for a turbine to generate power
D
  • Darrieus Turbine - Vertical axis wind turbine looks like eggbeater
  • Delta Connection - Connects three wires of three phase electricity to a load in a triangular formation
  • DFIG - Doubly fed induction generator where the rotor is made of windings and requires slip rings to connect to electricity
  • Diode - Semiconductor with two terminals, allows one way curent
  • DC - Direct Current type of electricity that flows in one direction
  • Direct Drive Mode - Connecting a turbine and generator without a gearbox
  • Discout Rate - economic term implies rate for borrowing money
  • Dispatch System - communication system where all participants are informed
  • Distribute Generation System - Electrical system with more than one generator, typically referring to many small sets of generators as opposed to centralized larger ones
  • Downwind Turbine - Turbine where wind hits tower before blades
  • Drive Gear - transfers energy to mating gear
  • Drag - component of aerodynamic force parallel to wind that slows down movement
  • Drag Coefficient - ratio of drag force to aerodynamic force causing it
  • Drag-Type Turbine - turbine based on drag forces
  • Drive Train - set of gears to obtain desired gear ratio
  • Dynamo - Direct Current Generator
E
  • Efficiency - Ratio of output energy to input energy
  • Electric Circuit - setup of electrical components powered by a source
  • Electric Load - consumer of electricity
    • resistive - load that has only resistance
    • capacitive - load consists of capacitors
    • inductive - contains windings
  • Electric Source - battery or generator providing power to a system
  • Electromagnet - magnet made of coil and ferromagnetic core, requires electric power for magnetism
  • Electromechanical System - Device with both moving and electric parts
  • Energy - Potential to do work, or force applied over a distance
  • Epicyclic Gear - Planetary Gear
  • EWEA - European Wind Energy Association
F
  • Fall Arrest - Stopping a fall from a height
  • Fatigue - repeated tension/compression stress
  • Fatigue Failure - failure of component due to fatigue
  • Feathered - Position of wind turbine blades with smalles lift and largest drag
  • Ferrous - Iron family of metals
  • Fixed Speed Mode - Turbine speed constant operation
  • Flashing - repeated reflection of sunshine on a turbine blade
  • Flicker - Short time voltage variation in power line due to disconnect of large load
  • Flickering - Shadowing effect of rotating blade
  • Flutter - Vibration of wind turbine blade about its own axis
  • Foundation - Massive block of concrete anchoring a tower
  • Free Wheel - Standby state of wind turbine where there is insufficient wind to turn turbine
  • Frequency - Number of repetitions in one second of cyclic phenomenon
  • Frequency Converter - Device that changes frequency of AC
  • Full-Wave Rectifier - 2 rectifier diodes that converts the entire cycle of AC to DC
  • Fuse - Protection device in electrical circuit that melts to open a circuit in the case of overheat
  • Future Value - value of money at future time
G
  • Gearbox - mechanical device in an enclosure, converts rotational speed
  • Gear - single part of gear system, gearbox component
    • Arm - part of planetary gear that holds the planetary gears together
    • Bevel - perpendicular axes connected gear
    • Driven Gear - receives energy from mating gear
    • Driving Gear - gives energy to mating Gear
    • Epicyclic Gear - Planetary Gear
    • Helical Gear - teeth are angled with respect to shaft axis to reduce backlash
    • Idler Gear - gear that stands in between two main gears to change direction of rotation
    • Internal Gear - gear in the form of ring with teeth on the inside
    • Planetary Gear - set of gears arranged in form consisting of sun gear in the middle, usually 3 planetary gears engaging with sun gear and outer ring gear with internal teeth, can accept two input speeds, mounted on bracket that can turn independently
    • Ring Gear - outermost gear with internal teeth in planetary gear
    • Spur Gear - gear with teeth parallel to axis of rotation
    • Sun Gear - innermost planetary gear
    • Worm gear - gear with high ratio to reduce speed, axes set at 90 degrees
  • Gear Ratio - ratio between output and input speeds in a set of gears
  • Gear train - set of gears arranged to obtain a specific gear ratio
  • Generator - machine that produces electricity, mechanical to electrical
    • Armature - windings on the rotating part in a generator or motor, current carrying windings on a moving part
    • Brush - electrical connector made of carbon or carbon composite, when electrical connection between rotating and stationary parts needed, slides on metallic rotating ring
    • Rotor - rotating part of generator
    • Stator - stationary part
  • Grid - Electric Network
H
  • Half-wave Rectifier - Simplest type of AC to DC rectifier one diode only accounts for half the wave transferred into DC
  • Harmonics - frequencies that are multiples of the fundamental frequency
  • Harness -  part of the protective equipment or catching the wind energy by a turbine
  • HAWT - Horizontal Axis Wind Turbine
  • Hertz - frequency unit
  • High-Speed Shaft - Output shaft in a wind turbine linked to generator shaft
  • HVDC - High Voltage Direct Current transmit electricity around 300 kV DC
  • Hub - part of propeller type wind turbine to connect blades
I
  • Ideal Transformer - Assumed transformer with zero loss
  • IEEE - Institute of Electrical and Electronics Engineers
  • Induction Generator - AC generator where rotor current is generated by induction than connection to electricity as in the synchronous generator
  • Inductive Reactance - Apparent resistance due to an inductor
  • Inertial Force - force required for acceleration or deceleration
  • Infrasound - sound with frequency below human hearing sometimes generated by wind turbines
  • Initial Cost - startup costs of a project
  • Inverter - converts DC to AC electricity
  • Islanding - isolation of a part of AC Network from rest resulting in frequency and voltage drift
  • ISO - International Standards Organization
  • Isolation Transformer - Transformer used to separate a circuit from the main device 
K
  • Kilowatt - a thousand watts
  • Kilowatt-hour - measures energy consumption
  • Kinetic energy - energy associated with motion
L
  • Lagging - current waveform behind the voltage waveform
  • Lanyard - part of safety equipment hooked to a safe point for fall arrest, contains spring piece
  • Lattice Tower - tower made from small pieces welded together into a truss
  • Leading - current waveform in front of voltage waveform
  • Lift - perpendicular aerodynamic force to direction of wind caused by pressure differential over an object
  • Lift Coefficient - ratio of lift force to aerodynamic force causing it
  • Lift-Type Turbine - turbine based on lift instead of drag
  • Lockout - locking a dangerous device from normal use
  • Lorentz Force - Force exerted on wire carrying a current inside Magnetic Field
M
  • Main Shaft - low speed shaft in gearbox connected to rotor
  • Maintenance - keeping a machine in operation
    • corrective - repair after failures occur
    • preventative - systematic repair regardless of state of machine
    • scheduled maintenance - regular planned repair
  • Met Tower - Meteorological Tower
  • Motor - converts electrical energy to mechanical
N
  • Nacelle - A room at the top of a turbine tower that houses gearbox, generator and other equipment
  • Natural Frequency - frequency inherent to object that can resonate
  • Net Present Value - economic term represents current revenues minus the total cost over lifetime of project
O
  • Offshore - on a lake or sea
  • Onshore - on land
  • Operating Costs - continuous expenses necessary to run endeavor, such as rent, purchase of raw materials, maintenance
  • Operating Speed - speed at which machine normally works
  • OSHA - Occupational Safety and Health Agency
  • Output - Product or result of a machine
  • Overspeed - Speed above entire capacity potentially dangerous to machine
P
  • Pad Mount - transformer mounted on flat surface
  • Peak Hours - Electricity consumption peak hours
  • Permanent Magnet - Magnet that is continuous without electrical input
  • PPE - Personal Protective Equipment
  • Phase Angle - angle between voltage and current waveform, time delay
  • Phase Current - Current passing through a load between each of two lines in 3 phase system
  • Phase voltage - voltage across each individual load in 3 phase system
  • Pinion - smaller gear in a pair of gears or the output gear in drive train
  • Pitch Angle - angle blade forms in reference to rotation about its axis, alters angle of attack
  • Pitch Circle - represent gears size
  • Pitch Control - action of controlling pitch angle of blades
  • Pole Mount - transformer mounted at top of electricity distribution post
  • Power - Work done in 1 second
    • Active - Power converted to heat or work
    • Reactive - power due to capacitor or inductor storage in one part of cycle given back in next part of cycle
    • Apparent - power generator supplies for consumption
    • Coefficient - in wind turbine must be less than Betz Limit ratio of electrical generation to what is in the wind
    • Curve - Operational expected power curve
    • Factor - ratio of active power to apparent power, smaller than 1
    • Factor Correction - improving the power factor of AC currents using capacitors
    • Plant - industrial unit for generation
    • quality - degree of agreement to expected stability requirement, 50 or 60 Hz
  • PPE - Personal Protection Equipment
  • Present Value of Money - value of money expressed for a future time in today's money
  • Prevailing Wind - Most common wind direction for an area
  • Prime Mover - Source of mechanical power turns a generator
  • Propeller Turbine - Turbine with blades similar to propeller, most common type of wind turbine
R
  • Rectifier - converts AC to DC
  • Renewable Energy - Energy from natural sources that is recoverable
  • Reluctance Force - Force by an electromagnet trying to shorten path of magnetic field
  • Ripple - Rapid fluctuations of voltage about nominal value in DC
  • Root of a Blade - end of blade attaching to hub
  • Rotating Magnetic Field - Magnetic field rotates about an axis, exists inside the stator of AC motors, basis of their operation
S
  • Savonious Rotor - drag type turbine that consists of two half cylinders
  • Scuffing - transfer of metal particles by tearing and adhesion from one tooth in a gear to another by welding
  • Shadow Flicker - Moving shadow cast by rotating blade
  • Shear Stress - stress due to a cutting force
  • Sine Wave - Sinusoidal wave function
  • Single - Phase - simplest AC electricity transmitted by 2 wires
  • Skew Wind - Wind whose direction is very far off from horizontal
  • Slip - act of not rotating at synchronous speed in induction motors and generators
  • Slip Ring - metallic ring on rotor of certain types of AC machines to transfer electric current
  • Slip Speed - difference between actual rotating speed and synchronous speed
  • Smart Grid - grid equipped with automated self correcting devices
  • Solidity - percentage of solid area traced in a circular rotor motion, blade area to total area
  • Spar Platform - platform in the form of a vertical cylinder top for wind turbine
  • Squirrel-Cage Motor - induction motor without windings, consists of bars connected by two rings, cage like structure
  • Stall - decrease in lift force until drag takes over
    • Control - use of stall to regulate motion of turbine
  • Star connection - connect wires in a y shape as opposed to a triangular shape
  • Step-down - lowering voltage
  • Step-up - increasing voltage
  • Substation - electrical utility to regulate electricity before sending to grid
  • Synchronous Generator - AC generator with one or more magnets, electricity generated in stator when rotor rotates at a fixed frequency
  • Synchronous Motor - AC motor where one or more magnets is within a rotating magnetic field causing rotor to follow the field, runs at multiples of synchronous speed
  • Synchronous Speed - constant speed of electrical machine dependent on frequency of supply
T
  • Tagout - put note on device or location as safety precaution
  • Tension Leg Platform - floating platform kept in place by cables attached to seabed under tension
  • Three-Phase System - requires 3 wires at least, each with fixed delay between them in voltage
  • Thyristor - control transistor used in rectifiers and inverters
  • Tip Speed - speed of tip of blade
    • Ratio - ratio of tip speed to wind speed
  • Torque - turning effort about a point perpendicular to rotational motion
  • Tower - support rotor and nacelle
    • Lattice - welded small structure support
    • Tubular - singular tube or conic shape support
  • Turns Ratio - ratio between number of turns in primary and secondary windings
U
  • Universal Motor - Type of motor that can work with both DC and single phase AC
  • Upwind Turbine - Wind turbine where blades are in front of tower and wind reaches blades before tower
V
  • Variable Slip Mode - Way of operation where wound rotor induction generator used with some power extracted
  • Variable Speed Mode - Synchronous generator that can operate at different instead of singular speed
  • VAWT - Vertical Axis Wind Turbine not sensitive to wind direction changes
  • Vector - quantity with both magnitude and direction
  • Volt - Electrical potential
  • Volt-Ampere - unit of measurement used to express apparent power, when voltage and current out of phase
    • VAR - Volt Ampere Reactive - measures reactive power
W
  • Watt - 1 Joule per second
  • Wind Data - Statistical information gathered about wind in a region
  • Wind Farm - region of multiple wind generators also called wind park
  • Wind Vane - measures wind direction
  • Work - used energy
  • Worm gear - high gear ratio used to reduce speed, driven gear cannot force drive gear to rotate
  • WRIM - Wound rotor induction machine whose rotor contains winding instead of squirrel cage
  • Wye Connection - also called star connection
Y
  • Yaw - action of orienting a wind turbine into direction of wind
  • Yaw Gear - gear system to rotate turbine for yaw motion
  • Yaw System - Entire gears and motors involved in Yaw motion of turbine

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