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Designing an application solution for wind turbines
Wind turbines are rotating machines that convert the wind’s kinetic energy into mechanical energy which in turn is converted into electricity.
Turbines used in wind farms for the commercial production of electric power have three blades, and motors controlled by servo drives point them in the direction of the wind. The blades have high tip speeds – up to six times the wind speed – and are highly efficient, with low torque ripple that contributes to good overall reliability. The blades range in length from 20 m to 40 m or more, and they can be controlled by Elmo’s high performance digital servo controller – the Tiger 50/600. Elmo’s Eagle 35/200 – a compact, high power and intelligent servo drive – is used as a backup drive to handle system operations in the event of an emergency or malfunction.
The blades rotate at 10 – 22 rpm, though the more advanced models operate at a constant speed. In this application solution, the servo drives control the motor blades which continuously change their angle with respect to the flow of the wind in order to maintain a constant rotational speed. All turbines are equipped with safety shut-down features to avoid damage at high wind speeds.
When designing an application solution based on Elmo’s products for a wind turbine, we are faced with the following challenges:
- The need for accurate, high speed control of the wind turbine’s tree blades.
- The ability to control the blades that are driven by DC brushless motors.
- The requirement to supply a high reliability solution in extreme and variable conditions.
- The need to provide a solution based on products that meet safety requirements and have redundancy/backup capabilities.
- The requirement to design a solution that is compact and uses minimum space.
- The ability to provide advanced programming capabilities within the drive to enable it to respond to unexpected situations.
- The need to supply a high power, cost effective and intelligent motion control solution.
- The requirement to provide Absolute Encoder support.
- The ability to connect directly to a three-phase mains supply without the need for a DC power supply.
The space limitations within the wind turbine for installing the servo drives requires compact electronics with very high power motor drives to supply the necessary high torque and accurately control the speed of the blades. The Tiger and Eagle drives are designed with high power density and high performance, where safety is an essential requirement.
The Tiger digital drive was chosen as the main driver due to its compact size, high power and ability to support up to a 600 VDC bus. It is a fully digital servo drive that can drive up to 50 A of continuous current that is required for the high torque that is necessary to drive the wind power blades at high speed.
The application implementation is based on proven, ready-for-use products, using the TIG 50/600 and EAG 35/200 as the main and auxiliary system controllers respectively. They were designed for very high performance servo systems that are usually used in high power military applications. The drives are MIL-STD compliant and can operate in extended environmental conditions (EEC). The Tiger is powered directly by three-phase mains power with no need for an additional DC power supply, as it has an internal integrated DC power supply. The Eagle serves as auxiliary backup that further increases system reliability. The TIG 50/600 and EAG 35/200 are highly reliable products that have been integrated in many military applications. The drivers’ reliability is not less than that of the wind turbine’s DC brushless motor.