Simply put, a diesel generator drives a generator.
In the cylinder, clean air filtered through the air filter mixes thoroughly with high-pressure atomized diesel injected from the fuel injector. The upward force of the piston compresses the air, causing it to shrink in volume and rapidly increase in temperature, reaching the diesel's ignition point. The diesel fuel ignites, and the mixture burns intensely, expanding rapidly, pushing the piston downward. This is called "work." Each cylinder performs work in a specific sequence. The thrust acting on the piston is converted through the connecting rod into a force that drives the crankshaft, thereby driving the crankshaft's rotation. By installing a brushless synchronous AC generator coaxially with the diesel generator's crankshaft, the generator's rotation drives the generator's rotor. Using the principle of electromagnetic induction, the generator generates an induced electromotive force, which, through a closed load circuit, generates current.
This only describes the basic operating principle of the generator set. To achieve usable and stable power output, a series of diesel generators, generator control and protection devices, and circuits are required.