| 摘要 |
<p>PURPOSE:To detect d.c. current equivalently including polarity with one set of current transformers and without using insulating amplifier by combining a gate block signal and output signal of current transformer. CONSTITUTION:Output of electric power source 1 is applied to a d.c. motor 6 through a positive side thyrstor cnverter 3 and a reverse side thyristor converter 4 which are controlled by a positive side gate block release signal 10 and a reverse side gate block release signal 11. On the other hand, output of a current transformer 2 is applied to a subtracter 20 through a rectifier 8 and a resistor 9. At the same time, output of the resistor 9 is applied to the substracter 20 through a relay controlled by a gain circuit 19 and the reverse side gate block release signal 11, and an equivalent d.c. signal I6 of polarity corresponding to d.c. current ID is obtained. By this way, detection can be made without using an expensive insulating amplifier and two sets of current transformers, and the cost of the detecting circuit can be reduced.</p> |
