| 摘要 |
1,213,210. Control of D.C. motors. SCHALTBAU G.m.b.H. 11 Dec., 1968 [13 Dec., 1967], No. 58823/68. Heading H2J. [Also in Division H3] A main thyristor 3 in a motor control circuit is switched off by an extinguishing thyristor 4 discharging a capacitor 5, whose charge is previously reversed by a reversing thyristor 6; and inductances 9, 6 in series with each of the extinguishing and reversing thyristors 4, 7 are arranged in the magnetic field of an inductance 8 in the main thyristor path whereby the switching action of the thyristors 4, 7 is enhanced. When the current source 1 is connected to the main thyristor 3 a pulse train is simultaneously applied to extinguishing thyristor 4 to turn it on so that the capacitor 5 is charged from the source 1. When main thyristor 3 is turned on, the reversing thyristor 6 is also turned on, and the charge on the capacitor 5 is reversed. When main thyristor 3 is to be turned off, the extinguishing thyristor 4 conducts the charge on the capacitor 5 to the cathode of the main thyristor 3 to reduce its current sufficiently to turn it off. The rising magnetic field of the inductance 8 during initial conduction of the main thyristor 3 causes the inductance 6 to boost the charge-reversing current flowing at that time through it; the capacitor finally has a voltage greater than that of the source 1. The collapsing magnetic field of inductance 8 during turn-off of the main thyristor 3, produces a boosted current in the inductance 9 which assists the extinguishing of thyristor 3. In modifications, a transformer (10, Fig. 2a, not shown) responds through a Zener diode 11 to the fall in voltage across the main thyristor 3 during initial conduction thereof and provides an increased charging voltage to the capacitor 5. Alternatively, a transformer (12, Fig. 2b, not shown) responds to the gate signal applied to thyristor 3, to apply an already reversed voltage directly to the capacitor 5 to increase the stored charge, thereby restoring energy in the capacitor 5 if the main thyristor 3 is maintained conductive for such a period that the capacitor 5 is prematurely discharged. |
