The SUPRAPOWER consortium, an EU FP7 funded research project, is developing an innovative 10 MW class superconducting generator (SCG) to provide an important breakthrough in the offshore wind industry. It is a partial SCG with MgB2 wires used in the field coils while conventional copper conductors are used in the armature coils. Due to the requirements of handling, maintenance, reliability of long-term offshore operation, the cooling system of SUPRAPOWER SCG adopts a modular and cryogen-free design. The SCG contains 48 identical superconducting coils and each coil is enveloped in one of the 48 identical modular cryostats. Benefiting from the modular concept, the key challenges of such innovative 10 MW SCG e.g. the modular superconducting (SC) coil and associated cryogenic systems could be validated through a scale-down experiment. This validator consists of two modular SC coils rotating together with the iron poles and yoke to generate the magnetic field. The modular cryostat enveloping the coil consists of a vacuum vessel, an active cooled thermal shield with multi-layer insulation and corresponding supporting structures. In order to achieve the SC coils working temperature of 20 K, a two-stage G-M cryocooler will be installed and linked to the two modular cryostats by means of conductive copper connection. A non-modular cryostat was developed to envelop the cold head of the cryocooler, the thermal link, and three binary current leads to feed electrically the coils while keeping the heat load from ambient as low as possible. A rotary union with Ferrofluid sealing was developed to transfer the helium gas between the rotating cold head and stationary oil-lubricated compressor. In this paper, the design and manufacture of each component will be described, and the assembly and preliminary experimental test of the cryogenic cooling system for the validator will be also presented.