Stepping motor driving by controlled-energy discharge

Stepping motors are indexing devices widely used in microcomputer-controlled machines. They have been proven to give excellent results in terms of accuracy and repeatability in many industrial applications. Their main weakness, however, is their relatively low working speeds (when compared to the alternative of servo motors), but this has been changing lately, mainly due to better electrical controller and motor designs. Hence, today there is a wider interchangeability range with servomotors. This paper describes a new electrical driving method for stepping motors based on controlled energy discharge over the motor windings. This method makes use of the fact that the time response of an LR circuit can be improved by the addition of an adequate capacitance. Experimental tests were performed for evaluation purposes. Results obtained show speeds reaching up to 6000 r/min and as much as 90% of the low-speed torque still available at 1000 r/min for a commercial-type stepping motor