Generators are other forms of energy into electrical energy machinery and equipment, first produced in the second industrial revolution, made by German engineer Siemens in 1866, which consists of turbine, steam turbine, diesel or other power-driven machinery, the water energy airflow, fuel combustion or nuclear fission into mechanical energy produced by the generator to pass, then converted to electricity by the generator. Generating a wide range of uses in industrial and agricultural production, national defense, science and technology and everyday life.
No-load characteristics:
When the generator is not connected to the load, the armature current is zero, called no-load operation. At this point of the three-phase stator windings only the magnetizing current If the load is induced electromotive force E0 (three phase), its size increases with the increase of If. However, since the motor magnetic circuit core saturated phenomenon, so the two are not proportional. Reflect Load EMF E0 and excitation current If the relationship is called load characteristic curve for synchronous generator.
Armature reaction:
When the generator connected to the symmetrical load, the armature windings of the three-phase current generates a rotating magnetic field to another, said armature reaction magnetic field. Its rotational speed coincides with the speed of the rotor is equal to two synchronous rotation. Armature reaction magnetic field and the magnetic field rotor synchronous generator excitation can be approximated by sinusoidal distribution are considered. The space between them depending on the time phase retardation load emf and the armature current I E0 between. Armature reaction magnetic field also load status. When the generator load is inductive, armature reaction from the field demagnetization effect, will cause the voltage of the generator is reduced; when the load was capacitive, the armature reaction magnetic field plays the role of aid will make the generator output voltage increased.
Load operating characteristics:
Mainly refers to the external characteristics and tuning features. The external characteristics of the rated speed when the excitation current and load power factor is constant, the relationship between the generator terminal voltage and load current I U between. Adjustment feature is the speed and terminal voltage rating, the load power factor is constant, the relationship between the excitation current If the load current I.
"China's power generators and power generator unit manufacturing industry sales forecast demand and investment analysis report Prospects" The data show the rate of change in voltage synchronous generator is about 20 to 40 percent. General industrial and household loads are required voltage remains substantially unchanged. To this end, as the load current increases, magnetizing current must be adjusted accordingly. Although the trends and external characteristics adjustment feature on the contrary, for purely resistive and inductive loads, it is rising, while the capacitive load, generally declining.
