The model was launched at the Husum Wind exhibition in September 2015. It features 68-metre blades.
Senvion said the new turbine is equipped with a "sound-optimised blade profile" and a new pitch control system.
The prototype has been installed on a 130-metre hybrid tower, but will also be available at 110 metres.
It has been designed for forested or mountainous low-wind areas, the manufacturer said.
The 3.4M140 will enter serial production by the end of the year, while the prototype undergoes testing at the Notus Energy site. Testing will take around a year, according to a Senvion spokeswoman.