| 摘要 |
<p>PURPOSE:To eliminate the contact of a weak field circuit in switching by firing a reverse blocking thyristor at weak field controlling time and connecting a branch resistor in parallel with a field coil. CONSTITUTION:When a weak field control command is produced in high speed power driving region at braking time, a gate signal is supplied to a reverse blocking thyristor FTH, and a branch resistor R is connected in parallel with a field coil F1. When the command is released by the return of a notch to all fields, the gate signal of a reverse blocking thyristor FTH is interrupted, and the current flow rate of a chopper CH is throttled. Thus, the thyristor FTH become OFF. In this manner, a switch for performing a weak field control can be eliminated in provision of a contact.</p> |
