| 摘要 |
A pulse control circuit for a reversible permanent magnet d.c. motor comprises first and second thyristors 14F, 14R and first and second transistor switches 15F, 15R arranged in a bridge circuit so that on conduction of the first thyristor 14F and first transistor switch 15F current flows in one direction from a d.c. source 12 through the motor armature 10 whereas on conduction of the second thyristor 14R and second transistor switch 15R the current flow is reversed. To drive the motor in a selected direction a continuous gating pulse is applied to the appropriate thyristor 14F or 14R and the corresponding transistor switch 15F, or 15R is switched on and off at a variable mark-to-space ratio. A freewheel diode 16F, 16R is connected across each thyristor. Regenerative braking can be effected by holding both thyristors 14F, 14R nonconducting and by switching on and off the transistor switch 15F, 15R associated with drive of the motor in the direction opposite to that in which the armature 10 is rotating a runther diode 17F, 17R being connected across each transistor switch to provide a freewheel path for the armature current during non-conducting periods of the transistor switch. |
