汽轮发电机实心转子中由短路稳态定子负序与零序电流所产生的电流及气隙磁场

THE CURRENTS PRODUCED IN THE SOLID ROTOR OF TURBOGENERATOR AND THE AIR GAP MAGNETIC FIELDS BOTH BY THE STATOR NEGATIVE-SEQUENCE CURRENT AND THE ZERO-SEQUENCE ONE AT THE STEADY STATE OF THE LINE TO LINE GROUNDED SHORT CIRCUIT

该文应用电磁场的解析分析法分析了在汽轮发电机处于两相对中点短路稳态下由定子负序电流aNi和零序电流0ai分别在实心转子中所感应的电流RNi和0Ri以及气隙磁场。通过电流分析发现,如果aNaII0>,则0RI就有可能大于RNI。通过磁场分析发现,定转子基波回路间的耦合系数1k与定转子三次谐波回路间的耦合系数3k非常接近。正因为如此,0RI与RNI的大小主要就由0aI与aNI的大小而定。这一结果与文[1]运用网络分析所获之结果完全吻合,无疑是对零序电流仅在转子产生微弱电流的传统观念的又一挑战。

In this paper, the currents produced in the solid rotor of turbogenerator and the air gap magnetic fields both by the stator negative-sequence current and the zero-sequence one at the steady state of the line to line grounded short circuit have been analysed by using the analytical methods of electromagnetic fields. We find that the current 0RI in the solid rotor produced by the stator zero-sequence current 0aIis larger than that one RNI produced by the stator negative-sequence current aNI, if 0aI is much larger than aNI. Furthermore, we find that the coupling coefficient 1k between the fundamental loops of the stator and rotor is nearly equal to that one 3k between the third harmonic loops of the stator and rotor. So, which is the larger, RNI or 0RI, mainly determined by which is the larger, 0aI or aNI itself. As a result, the conventional concept of zero-sequence current without having possibility to induce any noticeable current in the rotor loops must be corrected.