SWT-20KW Wind Turbine

Introduction SWT-20KW Wind Turbine

SWT-20KW small wind turbine variable pitch controlled is designed to meet demanding requirements from professional users of stand alone or grid connected wind turbines. SWT-20KW variable pitch wind turbine generator is ideal for replacement of diesel generators at rural telecom base stations, water pumps, gasoline stations or farms. The SWT-20KW pitch controlled wind turbine includes features and solutions for optimal power production, like active pitch and yaw together with variable speed operation. Systems for remote operation and monitoring ensure high availability, efficient maintenance and long service intervals. Carbon fibre blades and a direct drive permanent magnet generator are other features to meet the need from professional users.

Robust design

The SWT20 variable pitch wind turbine is designed to comply with the IEC 61400-2 Ed. 2 standard for small wind turbines. Strength analysis has been performed for the entire mechanical design. SWT20 is designed for service intervals of 5 years. The low-speed, direct drive permanent magnet generator in conjunction with the robust axis and bearing design withstands loads at extreme conditions. There are no electrical connections to the permanent magnet rotor of the generator. Since both the active pitch system and the active yaw system are elector-mechanical no hydraulic system is needed that would require frequent service and may cause leakage.

Efficient power generation

All components of SWT-20KW pitch controlled wind turbine generator are chosen and designed with efficiency in mind. The highly efficient blade design together with active pitch and variable turbine speed ensures that as much as possible of the incoming wind is transferred into power. The rotation is converted into electricity through a low-loss, direct drive permanent magnet generator. In the SWT20KW variable pitch wind turbine an ultra sonic wind sensor is used together with an active yaw control system to ensure optimum direction towards the wind.

Technical description

The SWT-20KW variable pitch wind turbine is a direct driven, variable speed, pitch controlled wind turbine. The direct drive approach means that the hub is directly connected to the generator without any gearbox. This improves performance, gives lower mechanical noise and increase the lifetime and service intervals of the turbine. Variable speed means that the rotational speed of the three blades connected to the hub are proportional to the wind speed. This will maximize the power output of the turbine, especially at low winds, and also gives the turbine a unique feature of being programmable to avoid certain speeds. This is very useful if there are any structural resonant problems at these frequencies. The electrically actuated pitch control system controls the angle of attack of all blades simultaneously. An active pitch control of the turbine minimizes the cut in wind speed of the turbine, and also provides a way of optimizing the energy output of the turbine as a function of available wind energy. The pitch control also has two other important functions. It can be used to minimize forces on the structure (i.e. tower structure) by changing the angle of attack if there are any unwanted structural movements. The other important function of the pitch control is to act as a safety system by controlling the blade angle to avoid over-speed conditions and to pitch the blades to a feathered position during too high winds.

Technical Parameters

Rotor diameter:	12.35m
Blades quantity:	3pcs
Direction:	always downwind
Blades material:	Carbon fiber reinforced plastic
Rated output Power:	20KW
Power supplied to Grid	24KW [in 5seconds]
Working voltage:	DC360V/500V,AC220V/380V
Annual average energy production:	50MWH (in rate 5m/s wind speed)
Working wind speed:	3-35m/s
Initial wind speed:	2.0m/s
Nominal wind speed:	9.0m/s（30.3mph）
Storm-stand:	up to 55m/s
Max rotate speed:	120r/min
Wind turbine type:	Three-phase, PMG Alternator
Working temperature:	from -40 to +60 C
Blade Pitch Control	Variable Pitch
Over-speed Protection	Aerodynamic brake + Electromechanical disc brake
Speed Regulate and Shut Down Methods	Auto-Yawing, Positive Pitch and Electric Magnet Switch.
Gearbox:	None, Direct Drive
Battery charge time:

Power Curve

Variable speed

The turbine speed ranges from 0 to 120 rpm and a maximum speed of 150 rpm is allowed during short periods of time. Power generation is started at 30 rpm where maximum power is reached at 120 rpm and a corresponding wind speed of 9 m/s.

Pitch control

The electrically controlled pitch system consists of a pitching mechanism and a direct drive, brushless servo motor. If the pitch motor speed is the same as the turbine speed there will be no change in blade angle. If the speed of the motor is increased with respect to turbine speed, the angle between the blade and the rotation axis will increase and conversely if the speed of the motor is decreased the blade angle will be reduced. In case of a critical failure or loss of power, the pitch motor is short-circuited. This will cause the blades to be automatically feathered by the rotation of the rotor, which will then stop.

Direct drive generator

The permanent magnet generator is directly connected to the hub and its rotor that holds the magnets is mounted on the main shaft. Since the stator of the generator is mounted into the aluminum house, directly exposed to the wind, an efficient cooling is achieved.

Rotor disc brake

The electrically actuated rotor disc brake serves both as an emergency brake and as a parking brake. The brake, together with the pitch system, forms two independent emergency braking systems. Normally, the rotor disc brake is used whenever the turbine has to be stopped completely. During high winds, above 20 m/s, the control system secures the turbine by pitching the blades to a feathered
position and the rotor disc brake is then engaged. The rotor disc brake is also used during service and maintenance. Since the brake is used mainly as a parking brake, the wear on the pads is very low and are normally not to be replaced during the lifetime of the turbine. The disc brake relies on an internal battery backup system to work.

Power System

The SWT20KW variable pitch can be configured in a variety of different power solutions, by changing the power cabinet located on the ground. In the standard version the SWT20 is equipped with power cabinet for grid connection which means that the turbine is connected to a grid and is delivering power when the wind is available. If the grid is lost, then the turbine will stop, avoiding power generation into the grid.

Yiled VS Average wind speed (m/s)

	Average wind speed		Average Energy Turbulence
SWT12.35-20KW Variablepitch wind turbine	m/s	mph	Ideal	15%	20%	25%
	4.5	10.1	37,960	32,266	30,368	28,470
	5	11.2	43,800	37.23	35,040	32,850
	5.5	12.3	55,480	47,158	44,384	41,610
	6	13.4	63,152	53,679	50,522	47,364
	Estimated Annual Energy Production (kWh)