| 摘要 |
<p>PURPOSE:To detect field missing, including opening and short circuit of field, of a synchronous phase modifier reliably with no time lag. CONSTITUTION:Output from an AC side current detector 6 for exciting current supply is passed through a rectifier 12 and a smoothing circuit 13 in order to obtain the field current Ie of a synchronous phase modifier. On the other hand, a voltage detector 8 detects the field voltage Vf of the synchronous phase modifier and comparators 14, 15 make decisions, respectively, whether Ie=0 and Vfnot equal to 0 are satisfied. An AND circuit 16 makes a decision whether these outputs are satisfied simultaneously while a timer 17 makes a decision whether such state endures for a predetermined time thus detecting an open state of field reliably with no time lag. Furthermore, perfect short circuit and imperfect short circuit of field can also be detected through similar constitution directly utilizing field voltage and current of the synchronous phase modifier.</p> |
