Turbine generator is a kind of synchronous generator. It is an electrical device that uses a steam turbine as the prime mover to rotate the rotor and uses the principle of electromagnetic induction to convert mechanical energy into electrical energy. It is mainly used in thermal power plants or nuclear power plants.
A steam turbine generator is a generator driven by a steam turbine. The superheated steam generated by the boiler enters the steam turbine and expands to do work, causing the blades to rotate to drive the generator to generate electricity. The waste steam after doing the work is sent back to the boiler for recycling through the condenser, circulating water pump, condensate pump, and feed water heating device
Turbine generator is a generator matching the steam turbine. Its speed is usually 3,000 rpm (at a frequency of 50 Hz) or 3600 rpm (at a frequency of 60 Hz). In order to reduce the mechanical stress and wind abrasion caused by centrifugal force, high-speed turbine generators generally have smaller rotor diameters and larger lengths (ie, slender rotors). This slender rotor limits the rotor size of large high-speed turbo-generators.
Due to the many reasons for the design, installation and operation of turbo-generators, the faults of turbo-generators are latent, which often results in a high failure rate of operating units in the actual production process. The purpose of condition monitoring and fault diagnosis of the turbo-generator is to check the defects of the turbo-generator at the initial stage of the fault, and to arrange the unit’s maintenance in a planned way to avoid major accidents. At the same time, it extends its mean time between failures and shortens its mean time to repair, reduces downtime, reduces maintenance costs, and increases the equipment utilization of power generation equipment.
Turbine generator is a power generation device that uses a steam turbine as the prime mover to drag the rotor to rotate and uses the principle of electromagnetic induction to convert mechanical energy into electrical energy. After the DC current is passed into the rotor windings of the generator, a rotor magnetic field is established. This magnetic field is called the main magnetic field, and it rotates with the turbine generator rotor. The magnetic flux comes out of one magnetic pole of the rotor, passes through the air gap, the stator core, and the air gap, and then enters another adjacent magnetic pole of the rotor, thereby forming a main magnetic flux loop. As the generator rotor rotates with the steam turbine, the generator poles rotate once, and the magnetic field lines of the main pole are sequentially cut by u, v, and w three-phase windings (wires) installed in the stator core. According to the law of electromagnetic induction, Three-phase alternating electromotive forces of different phases are induced in the windings.
Assume that the turbo-generator rotor has a pair of magnetic poles (that is, an N-pole and an S-pole). When the turbo-generator rotor and the steam-turbine rotor rotate coaxially at high speed, such as when the steam turbine rotates at 3000 rpm, the generator rotor Rotating at a constant speed of 50 cycles / second, the polarity of the magnetic pole must also be changed 50 times. Then the induced electromotive force in the stator winding of the generator is also changed 50 times, and the three-phase alternating electromotive force with different phases is induced in the stator three-phase winding. That is, a three-phase alternating electromotive force with a frequency of 50 Hz. At this time, if the ends of the three-phase windings of the generator stator (ie, the neutral point) are connected together and grounded, and the lead wires of the three-phase windings of the generator stator are connected to the electrical equipment, a current will flow. This process That is, the process of converting mechanical energy input into the turbine rotor into electrical energy.
The most basic components of a turbo-generator are the stator, rotor, excitation system and cooling system. stator
(1) Stator core. The stator core is an important part that forms the magnetic circuit and fixes the stator windings. It is usually made of 0.5mm or 3.5mm thick cold-rolled silicon steel sheets with good magnetic permeability. The stator core of a large steam turbine generator is large in size, and the silicon steel sheets are punched into a fan shape, and then assembled into a circle by using multiple pieces.
(2) Stator winding. The stator windings are embedded in the stator slots inside the stator core and are arranged in three phases at an angle of 120 ° with each other to ensure that the three-phase stator windings generate an electromotive force with a phase difference of 120 ° when the rotor rotates. Inside and below each slot are two sets of insulated conductors (also known as wire rods). Each wire rod is divided into a straight section (placed in the core slot) and two termination sections. The straight part is the effective edge of the conductor that cuts the magnetic lines of force and generates the induced electromotive force. The terminating part of the wire rod plays the role of connection. The related wire rods are connected according to certain rules to form the stator three-phase winding of the generator. The stator bars of small and medium turbo generators are solid bars, while large steam generators use internally cooled bars due to the need for heat dissipation, such as a number of solid bars and hollow water bars that can pass through water. Composed in parallel.
(3) Base and end cover. The function of the machine base is to support and fix the generator stator core. The machine base is generally welded with steel plates. It must have sufficient strength and rigidity and can meet the requirements of ventilation and heat dissipation. The function of the end cover is to cover both ends of the generator body, and to form a complete ventilation system inside the generator together with the base, the stator core and the rotor.
Rotor The rotor of a turbo generator is mainly composed of a rotor core, an excitation winding (rotor winding),
The guard ring and fan are one of the most important parts of the turbo-generator. Due to the high speed of the turbo-generator and the centrifugal force on the rotor, the rotors are slender and made of hidden poles to better fix the field windings.
(1) Rotor core. The generator rotor body is machined from alloy steel with high strength and good magnetic permeability. A groove for the field winding is milled axially along the surface of the rotor body. The arrangement of the grooves is generally radial, and the part between the grooves is teeth, commonly known as small teeth. The unprocessed part is generally called the big tooth. The big tooth, as the pole body of the magnetic pole, is the only way for the main magnetic flux.
(2) Excitation winding. The field winding is a concentric winding made up of several coils, and the coils are made of rectangular rectangular copper wire. After the field winding is placed in the slot, the linear part of the winding is compressed with a slot wedge, the end portion is fixed with a guard ring in the radial direction, and the mica block and the center ring are used in the axial direction. The lead-out wire of the field winding is connected to the slip ring through a conductive rod, and then led out by a brush.
(3) Guard ring and center ring. The turbo-generator rotates at a high speed, and the end of the field winding is subjected to a large centrifugal force, so a retaining ring and a center ring are used for fastening. The guard ring covers the end of the field winding tightly so that the winding end does not undergo radial displacement and deformation; the center ring is used to support the guard ring and prevent the end portion from moving axially.
(4) Collector ring. The slip ring is divided into positive and negative slip rings, which are made of hard and wear-resistant alloy forged steel, and are installed outside the excitation end of the generator rotor. The positive and negative collector rings are respectively connected to the two ends of the excitation winding through the leads, and are led to the generator excitation system by the brush device.
(5) The fan. Fans are installed at both ends of the rotor of the generator to speed up the circulation of gas in the stator core and the rotor and improve the cooling effect.
cooling system When the generator is running, various losses generated inside it will be converted into thermal energy, causing the generator to generate heat. Especially for large-scale turbo-generators, due to their slender structure, the heat in the middle is not easy to radiate, and the heating problem is even more serious. If the temperature of the generator is too high, it will directly affect the service life of the insulation, so cooling is a very important issue for large turbine generators.
Excitation system The main functions of the excitation system are: ① When the generator is running normally, the excitation current is supplied and automatically adjusted according to the load of the host to maintain a certain terminal voltage and reactive power output.
② When the generators are operated in parallel, the reactive power distribution is reasonable.
③ When the system has a sudden short-circuit fault, the generator can be strongly excited to improve the stability of the system operation. After the short-circuit fault is removed, the voltage quickly returns to normal.
④ When the load of the generator is suddenly reduced, it can be demagnetized forcibly to prevent the voltage from increasing excessively.
⑤ When the generator has an internal fault, such as an interturn short circuit or a two-point ground fault on the rotor, the generator can be automatically demagnetized or demagnetized.