1. Excitation system

The brushless exciter is located in closed space under the generator stator. The design of the “bell”-type exciter (Fig.2) which winding is fixed to the generator end at the flange is accepted in the design.

The rotor shaft is made conjointly with the flange to fasten a generator to the rotor shaft and with the disk to fasten an anchor casing. On the shaft there is the central current distributor to the turbogenerator exciter and two barrier-layer wheels. The external anchor is placed inside strong cylindrical rotating casing of the exciter. The exciter has two three-phase windings shifted by 30 el. degrees incorporated into two groups by a “star” layout. The diodes of a rotating transducer are protected by preventers and RC-networks.

At the exciter inducer there is a three-phase winding connected by a “star” layout. The control device includes an automatic regulator of excitation, blocks of set-points, limitations and protections. The transducer and the control device have 100% redundancy.

The excitation current from the exciter is supplied to the winding through the detachable contact joint by a current lead in the central boring of the shaft with an exit to each pole through current-carrying bolts.

2. Cooling system

The development experience of the machine of the similar capacity with hydrogen cooling was used during the creation of turbogenerator cooling system.

The machine cooling system is the helium one with circulation of cooling gas along a closed circuit inside a casing under the influence of the fans placed on a rotor shaft. Fans are placed from each side of the rotor and provide helium circulation along all the path of vent layout.

Heat is removed from a turbogenerator by helium-water gas coolers. Water circulates in gas coolers along closed circuit and is cooled in an external heat exchanger. Gas cooler itself is made of several gas-water units (modules) providing their reservation. The modules are placed inside a leak-tight enclosure separately from the generator and connected with it by gas ducts.

As it said above, helium of 2.63 MPa working pressure is used to cool a turbogenerator, and at that some elements are cooled indirectly (stator winding, lead-out busbars, exciter). Thus temperature field, first of all, that of core and winding of the rotor were studied. The studies were performed assuming that heat transfer processes in the systems cooled helium under increased pressure are obeyed to criterial equations. So, heat-transfer coefficient in the channels is the following 0.8 0.4 2 д 0.023 0 Re Pr ,еW/m d λ α = ,

where λ0 =0.161 W/m 0К – helium heat conductivity; dГ- hydraulic diameter of the channel; Re and Pr – Reynolds and Prandtl numbers.

Heat-transfer coefficient in gaps between a stator and a rotor and on the external surface of an yoke is the following 0.8104 ,еW/m2 450 1+ 0.25V p α = ,

where V – gas rate, m/s; p – helium pressure, atm.

Exciter cooling is provided by the supply of the part of cooled gas from the area of increased pressure of the generator stator to the generator vent system by vent tubes.

According to the data of study the excess of temperature of the active parts of generators is not more than 45-550 under operation in nominal mode at cold gas temperature of 400 С.