Vertical turbogenerator with helium cooling

Ya.B.Danilevich, member of the Russian Academy of Science, DEEP of RAS

E.Yu. Anishev, N.S.Delfontsev, V.I.Kostin

To be submitted to the HTR- 2004 Conference on High-Temperature Gas-Cooled Reactors

Beijing, China (Sep. 22-24, 2004)

OKB Mechanical Engineering and DEEP have developed the design of a vertical turbogenerator with helium cooling and a 300 MW brushless excitation system for a newgeneration NPP with a high-temperature helium reactor.

In contrast to available machines the generator has distinctive features requiring additional development and investigations.

They include the following:

- vertical design of turbogenerator

- winding insulation operable in helium medium

- electromagnetic bearings

- powered high-voltage sealed leads-in;

- operation modes.

The main parameters of the generator are the following: effective output is 292 MW, rotation frequency is 3000 rpm, nominal voltage is 20 kV, capacity factor is 0.85, efficiency is 0. 85.

0. Design

The turbogenerator (Fig.1) is placed inside a high-pressure vessel and is rotated by a helium gas turbine placed below, generator is connected with the turbine by a coupling. The generator with a brushless exciter is included in a leak-tight vessel which is filled with gaseous helium at the absolute pressure of 2.63 MPa, which is used to cool the machine.

The generator consists of stator and rotor and auxiliary structural elements providing normal functioning of equipment. The generator stator has a laminated core, end areas of the core have magnetic shunts allowing decrease of loss and reduction of heating caused end electromagnetic fields in end areas.

The stator winding is two-layer loop with F class insulation on thermosetting binding agents with transposition of 540º of elementary conductors in the slot section.

Winding overhangs are fastened by system of brackets with bandage rigs, by distance pieces, self-shrinking bandage cords with using self-forming gasket materials, glues, with subsequent sintering each of overhang zones in single monolithic structure.

In the lower part of the generator from the side of the turbine there is placed the system of girders providing connection of the generator bearing with the unit. The system of electromagnetic bearings with magnet “cushion” effect is provided. From the external side of the generator casing there is cylindrical enclosure of the unit vessel making closed leak-tight space isolated from the environment vessel.

The machine rotor is made of high-strength steel forging. For each slot the narrower sub-slot channels are cut to supply cooling gas to rotor coils. To reduce rigidity difference for cross section axes the idle slots filled with magnetic conductor insertions are made in rotor poles. The rotor winding of coil-type is made of electric strip copper of rectangular section. F class insulation of rotor windings is made of special high-reliable glass fiber gasket material. Duralumin wedges of special shape close each slot on the outside, and overhangs are retained by bandage ring made of high-strength nonmagnetic corrosion resistant steel.

In the rotor there is a damper system made of short-circuit end rings and copper stripes in rotor poles.