Abstract: The motor control for a universal or D.C. electric motor controlled by opposing SCRs in parallel includes a comparator for controlling timing of firing of the SCRs based on a comparison of a sensed motor speed error signal and a synchronous ramp and also includes a circuit for sensing motor current as representative of motor torque and generating a motor shut-down signal when the sensed torque or current is greater than a setpoint value. When the shut-down signal is generated, the sensed speed error signal is overridden or prevented from being input to the comparator by deactivation (reverse biasing) of a current switch (diode) and results in the SCRs being deactivated. When the motor is restarted, a soft start circuit provides an alternate gradually increasing speed signal to the comparator in lieu of the sensed speed error signal for a selected short time after restart to gradually increase motor speed.

Abstract: A bending machine with a rotatable bending shoe for bending conduit and pipe includes a digital electronic control system with memory for providing accurate bending control and accurate repeat bending of successive conduits or pipes to substantially the same angle. A sensor is provided for determining increment degrees of rotation of a gear in the bending shoe drive train with the increments correlated to a particular degree of rotation of the bending shoe. The sensor signals are input to counting and comparator devices to terminate bending after the shoe rotates the degrees stored in memory for a particular bend.