From the perspective of the development of AC synchronous generators, the excitation system has become one of the core components. The quality of the excitation system directly affects the performance and operational quality of the synchronous generator. The AC exciter is a rotating armature type AC synchronous generator. However, due to its working characteristics and the particularity of the load, it is different from the general AC synchronous generator. Attention should be paid to its particularity during the design.
The magnetic circuit design of the AC exciter: The output voltage of the AC exciter varies significantly with the load and operating temperature of the main generator. Correspondingly, its induced electromotive force also changes significantly. This is the load characteristic of the AC exciter. To meet the rated excitation requirements of the main generator, the magnetic circuit size design of the AC exciter should be based on the corresponding rated phase potential. That is, the magnetic flux density at the rated operating point of the AC exciter should be very low. Therefore, the utilization rate of its magnetic materials is extremely low. The volume of an AC exciter of the same capacity is larger than that of a general synchronous generator, and its weight is also heavier.
According to the requirements of JBP T33201122000 “Technical Conditions for Small Brushless Three-Phase Synchronous Generators”, the AC excitation machine should be capable of providing the excitation current required for the starting motor to withstand 150% of the rated current in a hot state without reducing the voltage value. Therefore, the excitation current required by the generator at this operating point can be regarded as the rated load point of the exciter, and a certain transient response margin should be reserved according to the existing load conditions.
To improve the dynamic characteristics of brushless generators, it is advisable to select a smaller short-circuit ratio (approximately 0.13 to 0.15) as much as possible to enhance the sensitivity of the excitation current and shorten the time constant. A smaller short-circuit ratio enables the exciter to be designed more economically, with a smaller volume and lighter weight.
Select a higher frequency to reduce the time constant of the exciter. The measure to increase the frequency of the exciter is to increase the number of pole pairs of the exciter. An increase in the number of pole pairs can reduce the number of turns per pole of the excitation winding, thereby effectively reducing its time constant.
For more questions about the generator set, please call the Beidou Power team. More than ten years of professional production and sales of power generation equipment experience, more professional engineer team to serve you, choose Beidou power is to choose rest assured, welcome on-site factory inspection.
Post time: Dec-15-2025