Turbo - Generator Type: QF Series 1. General The generator is a two pole, cylindrical rotor type synchronous machine, directly coupled with steam turbine. It has a closed-circuit cooling system to cool the stator core and rotor, including direct hydrogen cooling of field winding. The stator winding, leads and terminals are cooled by deionized water. The collector rings are cooled by air. Excitation system is of Static Silicon Excitation System, including excitation transformer, thyristors, and AVR. Generator auxiliary system provide control and/or supervision of the hydrogen, shaft sealing oil and stator winding cooling water. The lubricating oil and jacking oil for generator bearings is provided by same oil source of that for steam turbine. 2. Applicable Standard and Codes The equipment and materials shall be designed and constructed in accordance with the IEC standards. 3. Specification Type: Three phase alternating synchronous generator directly connected with steam turbine. Class of rating.. Continuous Rated Capacity....6 MW Rated frequency..50hz Rated voltage...6.3 KV Speed...3000rpm
Rated power factor.0.8 Class of insulation...stator: B Rotor: B Phase...3 Connection..2-Y Short circuit ratio 0.5 4. Construction of Generator 4.1 Ventilation and cooling system The indirect cooling method is employed for the generator. The ventilation passages adopt a type of radial multiple flow ventilation, under the pressure of fans. During operation, heat caused inside stator coils, rotor coils and stator core is dissipated away by cooling hydrogen, and hydrogen is cooled by gas coolers in turn. 4.2 Stator frame Stator frame is fabricated from steel plate which is rolled and welded to form the required shapes. It's function is to support the stator core, stator winding. and rotor, to provide cooling gas passage and contain hydrogen gas without leakage.the frame is designed with ample strength to withstand stress caused by hydrogen explosion. End plates, wrapper and internal section plates provide stiffness to support the core and avoid resonant vibration, and also form a series of annular region for inlet or outlet gas flow. The frame is hydrostatic tesed after fabricated by filling with water and pressurizing to the specified pressure to verify the reliability of the design, welds and material, and then gas-tight tested by filling air to the pressure for at least 24 hours to verify that it is gas-tight. 4.3 Stator core The stator core is laminated with 0.5mm thick non-orientation, cold-rolled silicon steel sheets; each punching is coated with insulation varnish. The stator core is supported and clamped inside the frame by key bars and core flanges at both ends, therefore, constituting a tight uniform core. 4.4 Stator winding
The stator winding is a type of conedouble-layer lap winding. Each stator bar is made up of several cooper strands which are separately insulated with polyester glass fiber. Furthermore, insulation system with epoxy mica paper has been utilized for ground insulation of stator bars, and corona suppression measures have been taken so as to prevent corona during operation. The stator coils are secured in the slot portion with insulation wedges, the side gaps of coils inside slots are stuffed are stuffed with epoxy semi-conductor fillers, and semiconductor fillers are placed in slot bottoms and between stator bars in the slot portion. A binding structure is employed for the end winding, in which, the end winding bracket is made of epoxy glass laminated plate, and it is fixed on the core flanges via brazen blocks. The pre-impregnated conformable material or insulation blocks are filled in between stator bars and brackets or binding rings, then cross-binding method is employed to tight them altogether, and the binding ropes used in this method are made of high strength polyester fiberglass, like the conformable material the ropes are pre-impregnated with epoxy resin, after the binding of end winding finished, hot cured process is carried out. 4.5 Stator leads The leads are extended out of the frame through insulation porcelain bushings, and are connected with bus of power plant through connectors. 4.5 Rotor The rotor forging is made of high strength alloy steel with good permeability and mechanical property. The retaining ring is made of high strength non-magnetic forged alloy steel. The retaining ring is of suspension structure, it is shrunk on the rotor body and is axially fixed with ring key. The axial fan is of propeller type with blade angles adjustable, and its blades are made of high strength aluminum die forging. The rotor coils are made of silver-bearing copper strips, the turn-to turn insulation of coils is conducted by adhibiting two layer of synthetic compound fiber paper onto the strips, and is cured by hot pressing.
The ground insulation of rotor winding, i.e. slot cell is a compound system which is formed by pressing epoxy mica paper, polyamide film and glass cloth together. Furthermore, the cell are covered outside with metal sheets so that hot spot on slot call can be prevented and cooling efficiency can be improved. Winding in slot portion is fixed by diving high strength alloy aluminum wedges, and wedges at ends of rotor body are made of a special aluminum bronze material. The rotor winding leads are led to the collector rings from center bore of shaft through radial and axial conductors. Both radial and axial conductors are made of alloy copper, and wrapped with insulation, and the collector rings are made of alloy steel. 4.6 Bearing and bearing bracket The bearing and gland seals are installed inside the bearing bracket. The bearings are of elliptical type and the contact surface between bearing pad and bearing bracket is of spherical surface. The gland seal is of double flow type. The ground insulation is provided for gland seals at exciter end, two streams of oil will flow through the seal ring, the sealing oil at hydrogen side and sealing oil at air side are designed as two independent enclosed circulation system. 5. Excitation system 5.1 General The generator will be furnished with potential source static silicon excitation system. The static silicon excitation system will be a " High initial response excitation system ".Excitation power will be supplied from an excitation transformer connected to generator terminals. The excitation system consists of the following equipment: Excitation transformer
Thyristor rectifier device Voltage regulator device Field breaker device Protection device Field flashing device 5.2 Excitation transformer Rated data of the excitation transformer will be as follows: Type self-cooled, indoor, enclosed, dry type Primary voltage..6.3 KV+/-5% Secondary voltage.500v Phase...three Frequency.. 50Hz 5.3 Thyristor rectifier Duplicate rectifiers shall be provided, each capable of supplying the total load including field forcing conditions. Each rectifier shall be housed in a separate cubicle with its own cooling fan. The rectifier is a 3 phase fully-controlled bridge circuit with thyristors in all two legs of each paralleled bridge. If one bridge fails, it shall be possible to continue operation at rated load. Full protection of the power converters against SCR's failures shall be provided. The identification of failure shall be indicated by a monitoring system with lamps and annunciators. 5.4 Accessories and auxiliaries The excitation system shall also be furnished with automatic voltage regulator, field
discharge and field flashing equipment.