The SWT-3.15-142 turbine uses 69-metre blades, manufactured by LM Wind Power. The hybrid-carbon blades were developed as part of joint project between the two companies.
Siemens said it expects its new 3.15MW prototype to be able to generate 10GWh a year at average wind speeds of only 6 m/s.
The turbine will go through testing at the site in Drantum, Denmark, and is due to be ready for serial production by the end of the year.
"With LM's hybrid-carbon blades and our successful direct-drive technology this model incorporates proven and highly efficient technology in all components, and we are confident that we can maintain short time to market," said Siemens Wind's head of technology Morten Rasmussen.
It will be available in a range of hub heights up to 165-metres, Siemens said, meaning a maximum tip height of roughly 234-metres.
This would make the turbine taller than Nordex's N131 model installed in June 2016, claimed to be the tallest onshore machine to-date.
Nordex's 3.3MW turbine was installed at a 164-metre hub height, with 65.5-metre blades, giving it a tip height of just under 230 metres.
Siemens' new prototype is installed at a lower hub height of 109-metres.
It is one of three direct-drive 3MW-range turbines unveiled by the manufacturer at the WindEnergy Hamburg show in September.
At the event, Siemens also launched the SWT-3.3-130LM low noise model, featuring reduced rotor speed as an aerodynamic add-ons, and the SWT-3.6-130 IEC II medium-wind turbine, which was certified by DNV GL in October.