Generators that enter the grid system must be synchronized. The synchronization requirements are the phase sequence, voltage magnitude of each phase, and the frequency between the generator and the system grid must be the same. Automatic control is required on the prime mover and generator excitation system to meet these requirements. This study proposes automatic adjustment of prime movers and excitation systems using a controlled rectifier from a constant AC voltage source to a variable DC voltage. Arduino Mega based settings for processing the measurement results of voltage sensors and frequency sensors from generators and grids. The difference in the measurement results of these sensors as a basis for control of the prime mover and excitation system. Arduino Mega sends the firing angle for setting the prime mover and excitation system to the Arduino Pro Mini in the controlled rectifier module for the prime mover and excitation system. The results showed the prime mover speed regulation resulted in a change in generator frequency with an increase of 1 rpm resulting in an increase of 0.0352 Hz. Setting the excitation voltage produces a change in the voltage of the generator Vrms with an increase in 1 volt of the excitation voltage resulting in an increase in the generator voltage of 4.0427 volts. The synchronous condition shown by the synchronronoscope, the difference in voltage and frequency of the generator with the three-phase power grid displayed by the synchronization module LCD is 0.13% for the voltage difference and 0.12% for the frequency difference, respectively.