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同步发电机失磁故障对电网稳定性和发电机安全运行会产生很大影响。在中国,超高压发电机（extra high voltagegenerator,EHVG）是新型的同步发电机,其失磁后对电网的影响还处于研究阶段。为准确模拟EHVG失磁故障发生后磁场分布情况,建立了EHVG场、路、运动直接耦合的时步有限元分析模型,以EHVG模拟样机为算例,通过试验证明该模型正确,方法可行。利用该模型对EHVG同步运行和失磁异步运行的瞬态磁场进行对比分析,得出了同步运行和稳态异步运行时气隙磁密基波幅值基本一致,而失磁异步运行时气隙磁密谐波幅值较大;且随着EHVG失磁,稳态异步运行前所带负荷的减少进入稳态异步运行时,气隙磁密谐波分量也逐渐减小,气隙合成磁密接近正弦波,为其运行提供基础数据。“,”There was a huge impact on the grid stability and safe operation of generators when loss of field fault was occurred on a generator.In this country,the effect of EHVG loss of field on the power grid was still in the research stage.For accurate simulating the magnetic field distribution of the EHVG loss of field,the time-stepping finite element model of the EHVG was built considering the couple of field,circuit and rotational movement.Simulations and tests showed that the model and the method are effective.By comparison of the transient field distributions under the synchronous operation with the steady-state asynchronous operation in case of field loss in the prototype of EHVG,Fundamental amplitudes of flux density in the air gap are found to be equal.But,when the EHVG is operating at the asynchronous steady state,its harmonics amplitudes of flux density in the air gap are larger,than that at the synchronous operation.It can been concluded that the less load before the generator get access to the steady-state asynchronous operation,the less harmonic components contained in the air gap where the synthesis magnetic potential is close to sinusoidal shape.