1. Job Characteristics: The main characteristics that indicate the performance of synchronous generators are the no-load characteristics and load operation characteristics. These characteristics serve as a crucial basis for users in selecting generators.

2. No-load Characteristics: When the generator is not connected to a load, the armature current is zero, which is referred to as no-load operation. At this point, the stator's three-phase winding of the motor only has the no-load electromotive force E0 (three-phase symmetrical) induced by the excitation current If. Its magnitude increases with the increase. However, due to the saturation phenomenon of the motor's magnetic circuit core, they 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 the synchronous generator.

3. Armature Reaction: After a generator is connected to a symmetrical load, the three-phase current in the armature winding generates an additional rotating magnetic field, known as the armature reaction field. Its speed is exactly equal to the speed of the rotor, rotating synchronously with it.

The armature reaction magnetic field of the synchronous generator and the excitation magnetic field of the rotor can both be approximately considered to be distributed in a sine wave pattern. 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 reaction magnetic field is also related to the load condition.

When the generator's load is inductive, the armature reaction magnetic field exerts a demagnetizing effect, leading to a decrease in generator voltage; when the load is capacitive, the armature reaction magnetic field has a magnetizing effect, causing the generator's output voltage to increase.