| 摘要 |
1326140 Control of D.C. motors CKD PRAHA OBOROVY PODNIK 19 April 1971 [4 April 1970] 23748/71 Heading H2J A running and braking circuit for a D.C. motor which facilitates a quick transition from running to braking by employing a scheme in which the motor acts as a series motor whilst the motor is running and as a shunt generator during braking of the motor comprises a switching circuit with two contactors. A running contactor 2 interrupts the power supply to a thyristor switch 1 in series with the motor 6, the field winding 4 and a parallel combination of a diode 5 and a braking resistance 9. For running the contactor 2 is closed and a braking contactor 3 is open and current flows in the combination described above when the switch 1 is closed. When the switch 1 is opened, after the current has reached a predetermined value, the current decays through a commutating diode 7 and the switch 1 closes once more hence maintaining the required current. For braking the motor, contactor 2 is open and contactor 3 is closed. The induced e.m.f. in the armature flows through a second diode 8, the switch 1, the field winding 4 and the contactor 3. This current has a rising characteristic and eventually opens the switch 1. The current then decays through two circuits; the field winding 4 and diode 7 with contactor 3 and the motor 6 and brake resistor 9 with contactor 3 and again the switch 1 closes hence maintaining the braking torque at the required value. A second circuit similar to the first is described with the power supply and diodes reversed. |
