Generator refers to the mechanical equipment that converts other forms of energy into electric energy. It is driven by water turbine, steam turbine, diesel engine or other power machinery, and converts the energy generated by water flow, air flow, fuel combustion or nuclear fission into mechanical energy to the generator, and then the generator converts it into electric energy.

Generators are widely used in industrial and agricultural production, national defense, science and technology and daily life. Generators come in many forms, but their working principles are based on the law of electromagnetic induction and the law of electromagnetic force. Therefore, the general principle of its construction is: with appropriate magnetic and conductive materials to form magnetic induction magnetic circuit and circuit, in order to generate electromagnetic power, to achieve the purpose of energy conversion.



Working Characteristics:

The performance of synchronous generator is characterized by no-load characteristics and load operation characteristics. Generator (FIG. 11)

These characteristics are the important basis for users to choose generators.

No load characteristics:

When the generator is not connected to the load, the armature current is zero, which is called no-load operation. At this time, the three-phase winding of the motor stator only has the no-load electromotive force E0 (three-phase symmetry) induced by the excitation current If, and its size increases with the increase of If. However, because of the motor magnetic circuit core saturation phenomenon, so the two are not proportional. The curve reflecting the relationship between the no-load electromotive force (E0) and the excitation current (If) is called the no-load characteristic of synchronous generator.

Armature reaction:

When the generator is connected to a symmetrical load, the three phase current in the armature winding will generate another rotating magnetic field, called the armature reactive magnetic field. Its speed is exactly equal to that of the rotor, and the two rotate simultaneously.

The armature reaction field and rotor excitation field of synchronous generator can be considered as sinusoidal distribution. The spatial phase difference between them depends on the temporal phase difference between the no-load electromotive force E0 and the armature current I. The armature reactive magnetic field is also related to the load. When the load of the generator is inductive, the armature reactive magnetic field will play a demagnetization role, which will lead to the voltage reduction of the generator. When the load is capacitive, the armature reactive magnetic field will act as magnetic aid, which will increase the output voltage of the generator.

Load operation characteristics:

It mainly refers to external characteristics and adjustment characteristics. The external characteristic is the relationship between the generator terminal voltage U and the load current I when the speed is rated and the excitation current and load power factor are constant. The adjustment characteristic is the relationship between the excitation current If and the load current I when the speed and terminal voltage are rated and the load power factor is constant.

The voltage variation rate of synchronous generator is about 20 ~ 40%. General industrial and domestic loads require the voltage to remain essentially constant. Therefore, as the load current increases, the excitation current must be adjusted accordingly. Although the tendency of the adjustment characteristic is opposite to that of the external characteristic, it goes up for inductive and purely resistive loads and generally goes down for capacitive loads