Generator set manufacturers offer different options for providing power to the automatic voltage regulator (AVR), and selection of the proper option is important to ensure correct operation of the generator set. While there are multiple options available for excitation systems, each has its own unique features that provide benefits for different applications. This is generally driven by the electrical characteristics of the loads and the short circuit performance requirements.
- Self-excited (Shunt)
Shunt (self-excited) excitation uses the output of the main stator to derive power for the input to the AVR.This same output is used for sensing the alternator output to continue properly regulating the voltage required for the input of the exciter.
- EBS (Excitation boost system)
The construction of this system follows the same setup of the shunt excitation for voltage sensing and power input to the AVR and also includes an excitation boost control (EBC) module and small excitation boost generator (EBG) added to the non-drive end of the alternator shaft. The EBS is engaged by the AVR when needed, eg during generator start-up or motor starting.
- PMG (Permanent Magnet Generator)
This PMG method places an additional small permanent magnet generator at the non-drive end of the alternator to produce power for the AVR. This permanent magnet generator output is isolated from the disturbances on the main output from the alternator and produces a clean, uninterrupted 3 phase waveform as long as the alternator shaft is turning, thereby preventing any disturbances to the input power of the AVR. The PMG provides reliable isolated power input to the AVR where significant voltage waveform distortion may have been a problem in a self-excited system.
The Auxiliary winding system uses the main field to generate power for the AVR through a separate winding on the stator. The winding is a separate single-phase winding which is inserted into the main stator alongside the main output winding