A turbine manufacturer has a new design for multi-MW offshore wind turbines, the medium speed permanent magnet generator (MS PNG) for the full converter concept. As a semi-integrated medium-speed generator, ABB’s new generator produces up to 8 MW or more. The generator and medium-speed gearbox are joined by a flange in a modular design. Using separate drivetrain components means low lifting weights that allow dismounting for service.
A PM generator is a synchronous electrical machine in which rotor windings have been replaced with permanent magnets. The main benefits are high power output from a small size, high efficiency at all speeds, and durable construction. The FC concept used with this system decouples the generator from the grid and offers total control and advanced grid compliance. For OEM’s, the new semi-integrated design offers a fast route to serial production of large offshore turbines.
Medium-speed generators deliver many benefits, the company says. A slower-speed design is more reliable for large offshore turbines while MS PMGs are also compact enough to offer relatively low top-head mass. Low weight means easier logistics as well as lower tower and foundation cost. MS PMGs are also said to offer the highest efficiency (>98%) of any commercial wind generator design. Efficiency is also high at partial loads in low winds and thus allows the largest annual power production.