In an effort to improve operating and technical characteristics and to eliminate some of the difficulties experienced when semi-skilled or unskilled persons are employed as drivers of electric locomotives in South African mines, an investigation was made to develop an improved, simple drive system having as many foolproof features as possible. A drive consisting of two compound-wound d.c. motors coupled differentially to the road wheels through an epicyclic-gear unit was examined and found to meet the requirements. Subsequent tests on a 4????????-ton experimental locomotive confirmed the features expected, and demonstrated in addition numerous useful characteristics not previously available on small locomotives. Ease and sensitivity of control, electric braking at any speed, exceptional manoeuvrability, inherent limitation of both tractive and braking efforts to prevent wheel-slip and skidding, virtual elimination of sparking at the controller contacts, limitation of motor loading and line current for any combination of controller position, drawbar load and speed, inherent automatic acceleration and maximum power economy at any speed and load are some of the more attractive features. The paper describes the drive and explains its basic characteristics by mathematical analysis.
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