Agricultural generator in operation has two characteristics : no-load characteristic and load operation characteristic. The no-load operation means the equipment is not connected, and the armature current is Zero.
In the process of no-load operation, the three-phase winding of the motor stator only has the no-load electromotive force E0 induced by the excitation current If. It increases effectively with the increase of If, but the two are not proportional because motor magnetic circuit core has saturation phenomenon.
When the agricultural generator connects to the load, the armature winding in the three-phase current will produce another rotating magnetic field, it is called the armature reaction magnetic field. Its speed is exactly the same as the rotor speed.
The armature reaction magnetic field and the rotor field magnetic field of the agricultural generator can be regarded as the distribution of sinusoidal law. The spatial phase difference between them depends on the time difference between the no-load electromotive force E0 and the armature current I.
The armature reaction magnetic field of the agricultural generator is also related to the load condition. When the load of the generator is inductive, the armature reaction magnetic field acts as a demagnetization, which leads to the decrease of the voltage of the generator. When the load is capacitive, the armature reaction magnetic field acts as a magnetic flux, and the output voltage of the generator Rises.
The load operation of the agricultural generator mainly refers to the external characteristics and the adjustment characteristics. The external characteristic is the relationship between the generator voltage U and the load current I when the excitation current and the load power factor are constant and the speed is rated , The adjustment characteristic is the relationship between the excitation current If and the load current I when the speed and terminal voltages are rated and the load power factor is constant.