Rheostatic stabilisation of a chopper-controlled brake for traction drives

This paper describes a means of dealing with and compensating for line-voltage decreases in chopper-controlled regenerative-brake equipment. The method of correction involves using a rheostatic brake resistor which is commonly available in such equipment and requies no extra power electronic circuit components. Electric braking can be maintained under all specified line-voltage conditions, as well as with a short circuit on the power supply line. With this arrangement full protection of the traction and chopper equipment is provided. A fast acting controller is proposed consisting of a closed-loop peak-current inner feedback loop with an outer loop controlling average armature current. Results of practical tests on a 250 A 400 V chopper are supported by numerically predicted results, obtained using a digital computer.