D.C. winder drives using mercury-arc rectifier/inverters

The high efficiency of mercury-arc-rectifier equipments would appear to make their use desirable on winder drives, on which efforts are continually being made to reduce hoisting costs. After outlining the requirements of a winding engine, the paper briefly describes a.c. and Ward Leonard drives, discusses their advantages and disadvantages, and compares them with a rectifier drive. The advantages of the latter led to the installation of such an equipment at Monk Bretton No. 3 Shaft, and the various rectifier connections and the methods of changing from rectification to inversion are considered. Various aspects of grid control and transformer design are discussed, and some rectifier faults are described, together with the protection provided against such faults. The winder is provided with closed-loop speed control and the system used is described. A comprehensive series of tests was carried out on the installation and the results obtained are illustrated.