Carlo Gavazzi is meeting the increasing demand for small-scale renewable energy sources with a complete package for residential or commercial wind power generation. The Mistral solution comprises of a 3kW micro wind turbine, braking control unit and inverter, enables users to generate electricity for the home or office, and feed surplus energy into the public grid.
Power is generated by a horizontal axis wind turbine (HAWT), which offers high efficiency with a low level of audible noise. The 2.6m diameter propeller provides a sweep area of 5.31m² and is integrated with a generator and tail atop a zinc-coated pole typically 6m in height. This 48.5kg unit makes use of lightweight, weather resistant materials: together with a specially-designed blade profile, it provides very high performance even in case of dominant wind turbulence. In harsh conditions, even when installed close to high buildings; this small turbine provides up to 39% of total efficiency. When the wind speed is more than 12.5m/s the safety “furling protection” tilts the mill tail, orientating the propeller diagonally to the wind direction, and forcing the propeller to slow down. In such condition the maximum power is also self limited to 3.3kW.
The generator is a three-phase permanent magnet unit with 18 electrical poles, designed to produce power even at low rotating speeds and providing a maximum output of 3.3kW. It is housed in a central body assembly, which also incorporates yaw bearings enabling the turbine to rotate and maintain the optimum heading. Electrical connections to the inverter and control system are via a slip ring located in the tower mount.
Three phase power at variable voltage is converted to a single-phase, 230VAC output at 50Hz, using the WTI3 inverter unit. A safety and monitoring system maintains efficiency to better than 95% and guarantees immunity from electro magnetic influence within international EMC standards. Full digital control ensures low current distortion of better than 3%, along with output frequency detection and synchronisation. Also integrated is Carlo Gavazzi’s maximum peak power tracking technology to maintain optimum wind power output. Active anti-islanding protection is provided for grid monitoring to ensure the highest levels of installer and user protection.
The WTB3 braking box sits between the generator and inverter, providing automated or manual control of the turbine. In its basic form, this unit ensures safe operation acting as the main breaker from the generator to the grid. The inverter drives two different electromagnetic brakes: a resistor brake, which operates when the wind speed goes above 13.5m/s, and a short-circuit brake that takes over if the resistor brake is activated repeatedly in a short time, or if the wind turbine speed increases despite the action of the resistor brake. In addition, manual brakes are provided via a mushroom switch and a maintained-action push button.
Braking unit and inverter are available separately or within a complete packaged wind turbine cabinet WTC3 that also integrates surge protection, along with the facility to monitor power output using a MID-compliant energy meter connected via an RS-485 interface, grid interface and breaker.
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