Control arrangementt for a wheel slip system

Claim 1

In a traction vehicle adapted to be powered from a source of alternating current and including a plurality of direct current electric traction motors each having serially connected armature and field windings, the motors being connected in driving relationship to a corresponding plurality of wheel and axle assemblies of the vehicle, rectifying means interposed between the alternating current source and the traction motors for converting the alternating current to direct current, a current transformer having a primary winding and at least one secondary winding, the primary winding being serially connected between the alternating current source and the rectifying means, means for selectively coupling the secondary winding in current supplying relationship to the field winding of at least a first one of the traction motors for supplying auxiliary current to that field winding during a wheel slip condition of the wheels driven by said first motor, the coupling means comprising auxiliary rectifying means for converting the auxiliary current from alternating current form to direct current form, controllable semiconductor means connected for selectively short-circuiting the transformer, and wheel slip detector means for sensing a wheel slip condition of the wheels driven by said first motor and for producing a wheel slip signal in response thereto, the improvement comprising: (a) amplifying means connected across said controllable semiconductor means and normally operative when the magnitude of voltage thereacross exceeds a relatively small threshold level to supply gating signals that maintain said semiconductor means in a substantially continuously conducting state whereby said current transformer is short circuited; and (b) connecting means disposed between said wheel slip detector means and said amplifying means for inhibiting operation of said amplifying means and thereby terminating said gating signals in response to the production of said wheel slip signal, whereupon said controllable semiconductor means reverts to a non-conducting state and auxiliary current flows from said current transformer to the field winding of the motor driving the slipping wheel.