How does the generator stator generate a magnetic field?

It depends on the excitation mode of DC motor. Excitation modes are mainly divided into two categories: 1. Separate excitation mode, which means that the excitation current of the magnetic field winding (stator winding) of the main magnetic pole is powered by another DC power supply, and there is no electrical connection with the armature circuit. You mean adding DC power to the stator. 2. Self excitation means that the excitation current of the excitation winding of the main magnetic pole is supplied by the armature of the motor itself. I guess what you want to ask is how to supply power to the magnetic pole (stator) in order to generate a magnetic field before the generator generates electricity, right! This is the use of residual magnetism. Before the generator generates power, the residual magnetism in the stator can meet the requirements of providing magnetic field. I have encountered that the generator has been idle for a long time, and there is no residual magnetism when it needs to generate power, so the generator cannot be started. An experienced master connects a battery to the stator winding and starts the generator to operate normally!