Power Plant Generator
The WX series air-cooled turbo enerator (6-200MW) is an air-cooled, self-ventilated machine with a cylindrical rotor. The rotor is cooled with air entering the hollow copper conductor directly, while the stator is indirectly cooled. There are two optional types of excitation systems for the series products: the brushless or static excitation.
These products feature in a compact structure, small volume, few auxiliary equipment, convenient installation, safe and reliable operation, long service life, easy maintenance, less first investment, and low running cost.
WX series turbo generators are designed with modular principle, including various types of 14L/Z, 16L/Z, 18L/Z and 23Z etc. These products are highly normalized and standardized. This kind of generators have been installed power plant projects in many nation's plant, and it is on of the most famous brand for medium sized power plants.
design is based on a horizontally split two-piece frame, which supports the stator core flexibly. This flexibility isolates the double frequency vibrations from the foundation.
The laminated stator core is build up of magnetic sheet segments made of high quality silicon steel coated on both sides with a heat-resisting varnish.
The winding bars are insulated by mica paper as the actual high-grade insulation material. At the slot ends, a corona-protection sleeve is added to provide the necessary stress grading between the slot end and the increasing voltage in the overhang region. The finished insulation meets the Class F specifications.
The Micadur-Compact Insulation System has been applied for the whole manufacturing process of the stator winding.
The wound stator core is impregnated under VPI plant-Micadur-Compact.
The high quality of the Micadur-Compact Insulation System achieves low dielectric losses, high dielectric strength, excellent thermal conductivity and a long life of insulation for 40 years.
The rotor body, together with the drive-end coupling flange, is machined from a single high-quality alloy steel forging-26NiCrMoV115.
The rotor winding
consists of hollow rectangular conductors of hard-drawn copper, which is alloyed with 0.1% silver to increase its strength at high temperatures. The winding is installed in the slots in such a way that it can expand uniformly outwards from the middle towards each end. This ensures smooth running during thermal changes with minimum sensitivity to fast load changes. All of the insulation materials used in the rotor comply with Class F specifications.
A damper winding is formed with winding slot wedges. Centrifugal force binds them together in the area of the end-bell seat to form a complete damper cage.
Rotor end bells are made of a high-quality austenitic stainless steel-18Mn18Cr and shrunk on to the body of the rotor in an overhang configuration.
The air-cooled turbo generators - WX series are equipped with the brushless excitation system, where as the brushless exciter comprises of the AC exciter and diode rectifier. The static silicon excitation can also be applied.
Automatic Voltage Regulator (AVR) is designed with double channel excitation system. It can be operated with a generator isolated operation and parallel with a networks.
The double channel excitation system consists of two individual channels: one is the main channels in operation for the regulation of the machine's terminal voltage, the other for servicing purposes and back-up for the main channel. A change over to the second takes place when the PT voltage of the main channel is failed or if excitation over-current is active. In both cases the system will switch automatically to the second channel. In order to ensure a smooth change over from the main channel to the standby channel and vice versa, an automatic follow-up is provided. The non-active controller always follows the active one.
The whole system offers comprehensive solution to all technical duties in this special field with modern, highly automatic and yet proven mean.
Two axial fans supply the self ventilated generator with cooling air. There are two parallel cooling air circuits, each fed by one of the axial fans. These cooling air circuits are symmetrical about the mid-plane of the generator.
The cooling air enters the rotor between the end-bell plate and the shaft, and flows into the end-winding chamber. At the inlet to the slots, the air runs into the hollow conductors. There it splits up into two portions. One portion flows through the hollow conductors in the slots. It reaches the center of the rotor, where it comes out into the air gap through radial holes in the hollow conductors and the slot wedges.
The other portion flows through the hollow conductors in the end winding. It reaches the polar axis, where it leaves the hollow conductors, ultimately emerging into the air gap through short slots in the end of the rotor body.