Construction of the HTW5.0-126 was originally expected to be finished by the end of March last year, with testing due to start by the end of September. Hitachi now says it will commission and begin testing the turbine this summer.
The new model combines a medium-speed generator with permanent magnet drive and features a rotor diameter of 126 metres.
The downwind model has been designed for typhoon-prone IEC-Class S (annual average wind speeds of 10m/s) locations, enabling it to withstand wind conditions typical in that region.
In February, the developers of a 220MW offshore project in Niigata province chose Hitachi to supply the 5MW turbine for the development.
Hitachi also said the turbine could be mounted on floating platforms. The Japanese company has already provided a 2MW turbine for the Fukushima floating offshore project, which started generating electricity in October.
In July 2012 Hitachi announced plans to build the 5MW turbine, a scaled-up version of the 2MW design the company acquired when it bought Fuji Heavy Industries' wind division turbine division in the same month.