Abstract: A method and apparatus are disclosed for controlling the wheel slip of an electric or diesel electric locomotive such that optimum wheel adhesion may be attained. A certain characteristic of a series traction motor, specifically the back emf per rpm versus motor current (E/n vs. I), forms the basis for a voltage control which limits the voltage (V) supply to each motor to a value which will limit the maximum percentage wheel slip. The selected limit value of wheel slip is great enough to encompass the conditions of maximum adhesion under most rail conditions. By combining the E/n with the motor IR drop, motor current, and a locomotive speed signal, the idealized voltage V for a non-slip condition is derived. This voltage is increased by a factor representing the desired maximum percentage slip to obtain the limiting voltage which may be supplied to the motor.

Abstract: In a feedback control circuit, a circuit maximizes or minimizes a controlled signal by incrementally varying the controlling signal in one sense, determining the direction of controlled signal change in response to such variation, and then incrementally varying the controlling signal in the same or the opposite sense in accordance with such direction. A condition of the system is that the controlled signal must reach a maximum or minimum in the range of the controlling signal. For illustration, the circuit is described in an analog-digital form applied to a wheel slip control of an electric locomotive to adjust the motor current to a maximum value to obtain the peak tractive effort that the rail conditions will permit.

Abstract: A method and apparatus are disclosed for controlling the wheel slip of an electric or diesel electric locomotive such that optimum wheel adhesion may be attained. A certain characteristic of a series traction motor, specifically the back emf per rpm versus motor current (E/n vs. I), forms the basis for a voltage control which limits the voltage (V) supply to each motor to a value which will limit the maximum percentage wheel slip. The selected limit value of wheel slip is great enough to encompass the conditions of maximum adhesion under most rail conditions. By combining the E/n with the motor IR drop, motor current, and a locomotive speed signal, the idealized voltage V for a non-slip condition is derived. This voltage is increased by a factor representing the desired maximum percentage slip to obtain the limiting voltage which may be supplied to the motor.