Brushless Electrically Excited Synchronous Machine Loss Analysis And Temperature Field Calculation

Since brushes and slip rings of brushless electrically excited synchronous machine(BEESM) are cancelled, BEESM does not produce spark, and it is suitable to use in inflammable and explosive environment. The structure of BEESM is simpler and more durable, and the operation is more reliable, and the maintenance costs are lower. BEESM has the advantages of conventional electrically excited synchronous machine excitation controllability. When BEESM connected to the grid operation or electric operation, adjusting the excitation current can change the power factor of BEESM; when BEESM off-grid power generation runtime, adjusting the excitation current can change the power winding end voltage of BEESM. BEESM has broad application prospects, and the operating mechanism of BEESM is more complex, so it has the problems of high loss and high temperature. In this paper, BEESM is used as the research object, the loss analysis, temperature field calculation and experimental study are carried out. Aiming at these problems, this paper carried out the following work:First, the structure, operation mode and magnetic field modulation mechanism of BEESM are summarized. The magnetic field of core, magnetic density of gap, inductance parameter and starting performance of BEESM with different rotor structures and operations mode are analyzed by finite element method.Second, stator copper loss, rotor copper loss, core loss, mechanical loss and stray loss of BEESM are calculated. Using different methods to calculate the loss coefficient of silicon steel sheet. The core loss calculation model considering the influence of the harmonic, rotating magnetization and skin effect is established, and the efficiency of BEESM is calculated according to the calculation result of the loss.In addition, based on the analysis of heat transfer characteristics of BEESM, the temperature field simulation model of BEESM is built by using Ansys Workbench finite element simulation software, at the same time, the equivalent treatment of the BEESM model is carried out, and the convective heat transfer coefficients of each surface are calculated. The influence of different cooling fin numbers, different cooling fin height, different casing surface wind speeds and different loads on temperature field of BEESM were analyzed.Finally, BEESM with two kinds of rotors is processed and manufactured. The experimental platforms of BEESM for electric operation and power generation are set up. The stator winding resistance was measured by bridge method, and the inductance parameters are measured by the static measurement method. The loss and performance of BEESM with different rotor structures and different operating modes are studied. The temperature rise of power winding, excitation winding and surface of casing are measured by using the thermal resistance and infrared thermometer. The results are compared with the simulation results.