Generator refers to mechanical equipment that converts other forms of energy into electrical energy. It is driven by water turbines, steam turbines, diesel engines or other power machinery. It converts the energy generated by water flow, gas flow, fuel combustion or nuclear fission into mechanical energy and transmits it to the generator. It is then converted into electricity by a generator.

Generators are widely used in industrial and agricultural production, national defense, technology and daily life. There are many forms of generators, but their working principles are based on the law of electromagnetic induction and the law of electromagnetic force. Therefore, the general principle of its structure is: use appropriate magnetically conductive and conductive materials to form magnetic circuits and circuits that perform electromagnetic induction with each other to generate electromagnetic power and achieve the purpose of energy conversion.

Working characteristics:

The characteristics of synchronous generators are mainly no-load characteristics and load operation characteristics. Generator (Figure 11)

These characteristics are an important basis for users to choose a generator.

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 windings of the motor stator only have no-load electromotive force E0 (three-phase symmetry) induced by the exciting current If, and its size increases with the increase of If. However, due to the saturation phenomenon of the magnetic core of the motor, the two are not proportional. The curve reflecting the relationship between the no-load electromotive force E0 and the exciting current If is called the no-load characteristic of the synchronous generator.

Armature response:

When the generator is connected to a symmetrical load, the three-phase current in the armature winding will generate another rotating magnetic field, which is called the armature reaction magnetic field. Its rotation speed is exactly equal to the rotation speed of the rotor, and both rotate synchronously.

Both the armature reaction magnetic field and the rotor excitation magnetic field of a synchronous generator can be approximately considered to be distributed according to a sine law. The spatial phase difference between them depends on the time phase difference between the no-load electromotive force E0 and the armature current I. The armature response magnetic field is also related to the load situation. When the load of the generator is inductive, the armature's reaction magnetic field plays a demagnetizing effect, which will cause the voltage of the generator to decrease; when the load is capacitive, the armature's reaction magnetic field will act as a magnetizing effect, which will cause the output voltage of the generator Rise.

Load operation characteristics:

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 the rated value, the excitation current and the 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 values and the load power factor is constant.

The voltage change rate of the synchronous generator is about 20 to 40%. General industrial and domestic loads require voltages to remain essentially constant. For this reason, as the load current increases, the excitation current must be adjusted accordingly. Although the changing trend of the adjustment characteristics is exactly the opposite of the external characteristics, it increases for inductive and purely resistive loads, and generally decreases for capacitive loads.