What's the principle of steam turbine generator?

What is a steam turbine generator?

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, which makes the blades rotate to drive the generator to generate electricity.

Back pressure steam turbine principle

A steam turbine generator is a power generation device that uses a steam turbine as the prime mover to drive 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 winding of the generator, the rotor magnetic field is established, which is called the main magnetic field, and it rotates with the rotor of the turbo-generator. The magnetic flux comes out from one magnetic pole of the rotor, passes through the air gap, the stator core, the air gap, and then enters the other adjacent magnetic pole of the rotor, thereby forming the main magnetic flux loop. Since the generator rotor rotates with the steam turbine, the generator magnetic pole rotates once, and the magnetic field lines of the main magnetic pole are cut in turn by the u, v, w three-phase windings (conductors) installed in the stator iron core. According to the law of electromagnetic induction, in the three-phase stator Three-phase alternating electromotive force with different phases is induced in the winding.

Assuming that the turbine generator rotor has a pair of magnetic poles (that is, one N pole and one S pole), when the turbine generator rotor and the turbine rotor rotate coaxially at high speed, such as when the turbine rotates at 3000 rpm, the generator rotor will Rotating at a constant speed of 50 cycles/second, the polarity of the magnetic pole also changes 50 times, then the induced electromotive force in the stator winding of the generator also changes 50 times, and at the same time, three-phase alternating electromotive force with different phases is induced in the three-phase winding of the stator. 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 (that is, the neutral point) are connected to the ground, and the lead wire of the first end of the three-phase winding of the generator stator is connected to the electrical equipment, current will flow. This process It is the process of converting the mechanical energy input by the steam turbine rotor into electrical energy.

A generator is an electrical machine that converts mechanical energy into electrical energy, usually driven by a steam turbine, water turbine, or internal combustion engine. Generators are divided into two categories: DC generators and AC generators, the latter can be divided into synchronous generators and asynchronous generators. Synchronous generators are most commonly used in modern power plants. It is excited by DC current and can provide both active power and reactive power to meet the needs of various loads. The asynchronous generator does not have an independent excitation winding, its structure is simple and the operation is convenient, but it cannot provide reactive power to the load. Therefore, the asynchronous generator must be connected in parallel with other synchronous generators, or a considerable number of capacitors must be connected in parallel. The DC generator has a commutator, the structure is complex, the price is more expensive, it is prone to failure, the maintenance is difficult, and the efficiency is not as good as that of the AC generator. Therefore, since the 1950s, the DC generator has been gradually replaced by the DC power obtained by the rectification of the AC power supply by the power semiconductor.

A steam turbine generator is a generator matched with a steam turbine. Its rotational speed is usually 3000 rpm (frequency of 50 Hz) or 3600 rpm (frequency of 60 Hz). In order to reduce the mechanical stress caused by centrifugal force and reduce wind wear in high-speed turbo-generators, the diameter of the rotor is generally small and the length is large (ie, a slender rotor). Such elongated rotors limit the size of the rotors of large high-speed turbo-generators. After the 1970s, the maximum capacity of steam turbine generators reached 1.3 to 1.5 million kilowatts.

A steam turbine generator is a kind of synchronous generator. It is an electrical device that uses a steam turbine as the prime mover to drive the rotor to rotate, 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.

Due to many reasons in the design, installation and operation of the turbo-generator, the failure of the turbo-generator is latent, which often causes the failure rate of the operating unit to remain high in the actual production process. The purpose of the condition monitoring and fault diagnosis of the turbo-generator is to check the defects of the turbo-generator in the initial stage of the fault, and arrange the maintenance of the unit in a planned way to avoid the occurrence of major accidents. At the same time, it prolongs its mean time between failures and shortens the mean repair time, reduces downtime, reduces maintenance costs, and improves the equipment utilization rate of power generation equipment.