Study On Parallel Structure Hybrid Excitation Brushless Claw-pole Alternator

Claw-pole alternator is widely used in the area of automotive field due to its simple structure and low cost. In recent years, with the improvement of whole capability, higher requirements are put forward to automotive generators; the concrete requirements are as follows:low excitation capacity, convenient magnetic field regulation, reliable operation, high power density. Common silicon rectification generator has shortcomings such as complex structure, low reliability and inconvenient maintenance. Hybrid excitation brushless claw-pole alternator has drawn considerable attention by its advantages of high flux density and power density, good performance in low speed and low excitation losses.A new parallel structure hybrid excitation brushless claw-pole alternator is proposed in this thesis, its structure character and operation principles are introduced. By using three-dimensional finite element method and equivalent magnetic circuit network method, magnetic field performance is analyzed. The main studies of this thesis are as follows:(1) A new parallel structure hybrid excitation brushless claw-pole alternator is proposed, which combines the advantages between electrical generators and magnetic generators and overcomes the disadvantages between them at the extreme, meanwhile, in this machine, the excitation can be easily regulated. The existence of permanent magnet makes magnetic flux of the air-gap increase and leakage flux decrease.(2) By using Ansoft/Maxwell3D finite element software, three dimensional finite element model of the motor under a pair of poles is set up, magnetic field distribution under no-load condition, adjustment characteristic under different excitation currents and no-load magnetic leakage field are analyzed. With contrast of no-load characteristic of the electrical excitation claw-pole motor with the same parameters, it can be found that, hybrid excitation structure can greatly decrease the leakage flux in the claw-poles and increase flux density of the air-gap. High air-gap flux density can be produced under lower excitation currents, which improves efficiency of the machine.(3) By changing rotor parameters of the hybrid excitation claw-pole alternator, the influence on air-gap flux density, leakage flux and magnetic saturation produced by the structure parameters such as palm thickness and yoke height of claw-pole rotor can be obtained based on Ansoft/Maxwell3D analysis. Therefore, appropriate parameters of claw-pole rotor can be obtained.(4) In consideration of the particularity and complexity of flux distribution in claw-pole machines, equivalent magnetic circuit network model considering3D filed distribution is put forward. The flux distribution under no-load operation by using MMFs node equations is analyzed. By comparing with3D finite element method, it can be obtained that the calculation results of these methods are consistent; meanwhile, the requirement of calculation accuracy can be satisfied. Moreover, the method of equivalent magnetic circuit network provides a powerful tool in reducing the split element quantities, saving computer memory and computation time.