The remaining magnetic flux of the generator core disappears or is too weak, causing vibration during long-distance transportation of the new machine. If the generator is placed for too long, the remaining magnetic flux voltage of the generator disappears or is less than the normal remaining magnetic flux voltage. That is, the residual flux line voltage is less than 10V, and the residual flux phase voltage is less than 6V. The stator and rotor cores of synchronous generators, as well as those of AC exciters, are usually overlapped and stamped with 1-1.5mm thick silicon steel sheets. Excitation can easily cause residual magnetism to disappear or weaken.

励磁回路接线不正确。修理发电机时，励磁绕组的极性意外逆转。通电后，由励磁绕组的电流中产生的磁场向剩馀磁化的反方向移动，剩馀磁化消失。此外，如果在维护过程中测量励磁绕组的DC电阻，或者在没有考虑极性的情况下测试自动调节器AVR励磁绕组的DC电流，铁心的剩馀磁通就会消失。

The excitation circuit wiring is incorrect. When repairing the generator, the polarity of the excitation winding unexpectedly reversed. After being energized, the magnetic field generated by the current in the excitation winding moves in the opposite direction of residual magnetization, and residual magnetization disappears. In addition, if the DC resistance of the excitation winding is measured during maintenance, or the DC current of the AVR excitation winding of the automatic regulator is tested without considering polarity, the residual magnetic flux of the iron core will disappear.

励磁回路堵塞，发电机励磁回路电气接触不畅，各种电气部件连接器松动，导线断开，电路中断，交流发电机励磁绕组不再有励磁电流流过。

The excitation circuit is blocked, the electrical contact of the generator excitation circuit is not smooth, the connectors of various electrical components are loose, the wires are disconnected, the circuit is interrupted, and there is no longer excitation current flowing through the excitation winding of the AC generator.

旋转整流器的DC侧电路被切断。由于旋转整流器直流侧电路的断路，励磁机经旋转整流器整流后，提供给励磁绕组的励磁电流不再输送给励磁绕组，交流同步发电机无法发电。

The DC side circuit of the rotating rectifier is cut off. Due to the open circuit in the DC side circuit of the rotating rectifier, the excitation current provided to the excitation winding is no longer transmitted to the excitation winding after the exciter is rectified by the rotating rectifier, and the AC synchronous generator cannot generate electricity.

由于交流励磁机故障，没有输出电压。由于交流励磁机不能产生电压，所以交流同步发电机的励磁绕组中没有励磁电流。

Due to a malfunction of the AC exciter, there is no output voltage. Due to the inability of the AC exciter to generate voltage, there is no excitation current in the excitation winding of the AC synchronous generator.

发电机励磁绕组损坏或接地。极低发电机的无励磁电流或励磁电流。

The excitation winding of the generator is damaged or grounded. The non excitation current or excitation current of an extremely low generator.

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