| 摘要 |
<p>PURPOSE:To detect a field abnormality without providing a special detection coil by obtaining a power factor angle by a voltage, a current, obtaining a field current at the time of loading from a field current, three-phase short-circuit rated currents corresponding to a non load rated terminal voltage corrected by the angle and a frequency, and comparing it with an actual field current. CONSTITUTION:A phase angle is detected by a phase angle detector 23 by outputs of a current detector 21 and a voltage detector 22, a correction value of a field current with respect to a no load rated terminal voltage is calculated by a field current corrector 28 based on a frequency detected by a frequency detector 27, and a correction value of a three-phase short-circuit rated current is calculated by a field current corrector 29. A field current at the time of loading is obtained by a field current calculator 30 by using them, compared with actual field current detected by a field, current detector 31 by a comparator 32 to detect a field abnormality.</p> |
