The Study On Integrated Brushless Excitation AC Synchronous Generator

The brushless excitation generators can avoid ring fire,simplify the maintenance,and improve the reliability of the generation system.However,some problems still exist in many methods: 1.The output waveform is not sinusoidal and the quality of the output waveform should be improved.2.The iron cores are solid because the axial flux and the iron loss is increased.3.The volume of the generation system is larger because of the exciter.4.The output power cannot be regulated and the original operating characteristics are changed.5.The loss is increased because the excitation power is high.In order to solve the above-mentioned problems,an integrated brushless excitation method is proposed and used for the realisation of the brushless excitation for a rotor-wound hybrid excitation synchronous generator.And,the new generator is called Integrated Brushless Excitation Hybrid Excitation Synchronous Generator(IBE-HESG).The main contents of this paper are as follows: 1)A novel integrated brushless excitation method is proposed to realise the brushless excitation for the rotor-wound generator and IBE-HESG is designed by this method.The operating integrated brushless excitation method and IBE-HESG are studied,the method for the design of the number of the pole-pairs of the main generator section and excitation section is analysed.A 1.5kVA prototype is designed and the parameters of the main generator section is optimised,the finite element model of is built by Ansys Maxwell and the prototype is fabricated.The magnetic field distribution of the IBEHESG is obtained.It can be concluded that the magnetic field distribution is controlled by the stator excitation current and the merit of the rotor-wound generator is remained.Compared with the magnetic field distribution of the brush excitation generator,it can be seen that the excitation section has little effect on the main generator section.2)The magnetic field of the main generator section and excitation section is coupled.It is decoupled by the superposition and frozen permeability method.The rotor-pole-body,rotor tooth,stator yoke,stator tooth and air gap are chosen to be analysed.The main generator section and excitation section are regarded as the main generator and exciter in the generation system with the exciter respectively by the superposition.The influence of the coupling to magnetic field can be studied by comparison of the results of the superposition with the results of the frozen permeability method.It can be concluded that the field distribution of the two parts does not affect each other significantly when the iron core is not saturated.Also,it can be analysed that the excitation section will not lead to the demagnetisation of the permanent magnets and the operating characteristic of the main generator section.3)The voltage regulation ability of IBE-HESG is determined by the excitation characteristic.Therefore,the excitation characteristic of is studied.The influencing parameters and the operating features of the rotating rectifier are analysed.The equivalent circuit and vector drawing of the excitation section is studied to optimise the excitation characteristic of excitation section.The relatively good parameters are designed by finite element analysis and experiment.Both the improvement of the excitation efficiency and sensitivity of the excitation characteristics are taken into consideration.4)In order to obtain the operating characteristics of the IBE-HESG and brush excitation HESG,the operating characterises under no-load condition and load condition are obtained by the Ansys Maxwell and the test of the prototype.The output voltage,regulation characteristic,excitation characteristic and loss are studied.It is demonstrated that the operating characteristic of the brush excitation HESG is remained by the integrated brushless excitation method while the brushless excitation is realised.It can be concluded that IBE-HESG has many merits,such as wide voltage controlled range,good linearity of excitation characteristic,low voltage regulation rate,high efficiency.IBE HESG has good prospect because of excellent operation characteristics.Finally,the integrated brushless excitation method is applied in an electrical excitation synchronous generator.It is demonstrated the feasibility of the integrated brushless excitation method in realisation of the brushless excitation.