Motor control system having improved dynamic braking

A motor control system for a reversible series DC electric motor, said motor having an output shaft adapted to be connected to a driven member, and said system when energized operable to rotate said output shaft to move said driven member and when energization is removed to smoothly, rapidly, and consistently stop rotation of said output shaft and movement of said driven member, said control system comprising:

• a DC source having output terminals of predetermined polarities;
• a motor field winding forming an integral part of said series DC motor, a bridge circuit conformed as a full-wave rectifier and having DC terminals of different polarities and AC terminals, said motor field winding electrically connecting between one output terminal of said DC source and the one DC terminal of said full-wave rectifier bridge which has a polarity opposite to the polarity of said one output terminal of said DC source, and the other DC terminal of said full-wave rectifier bridge connecting to said one output terminal of said DC source;
• a rotatable motor armature having two electric terminals and forming an integral part of said series DC motor, said motor armature connecting to and operable to drive said rotatable output shaft, one electric terminal of said motor armature adapted to be connected via one AC terminal of said full-wave rectifier bridge to said one DC terminal of said bridge, a first controllable open or closed switch connected in circuit between said one motor armature terminal and said one DC terminal of said bridge, the other electric terminal of said motor armature adapted to be connected via said other AC terminal of said bridge to said one DC terminal of said bridge, a second controllable open or closed switch connected in circuit between said other motor armature terminal and said one DC terminal of said bridge, said other electric terminal of said motor armature also adapted to be connected via a third controllable open or closed switch to the other output terminal of said DC source, and said one electric terminal of said motor armature also adapted to be connected via a fourth controllable open or closed switch to said other output terminal of said DC source;
• and means for selectively controlling the opening and closing of said open or closed switches including the following open and closed relationships to produce the following system functions:
• when said first and third switches are closed and said second and fourth switches are open, said armature and connected output shaft rotate in one direction to move said driven member in one predetermined direction;
• when said second and fourth switches are closed and said first and third switches are open, said armature and connected output shaft rotate in an opposite direction to move said driven member in another predetermined direction;
• and when said first and second switches are closed and said third and fourth switches are open, any rotation of said armature and output shaft and movement of said driven member are smoothly and rapidly dynamically braked.