Mechanics of train movement:
Essential driving mechanism of an electric locomotive is shown in fig. The armature of the driving motor has a pinion diameter d‟ attached to it. The tractive effort at the edge of the pinion is transferred to the driving wheel by means of a gear wheel.
Tractive effort transferred tot the driving is given by the expression.
F = = η F (d/D0 = η 2T/D) = ηT (2/D) (d/d) = ηT 2y/D
Where T is the torque exerted in N-m, by the driving motor, d is the diameter of gear wheel in metres. D is the diameter of driving wheel in metres, η is the transmission efficiency and γ is the gear ratio and is equal to d/d‟
For obtaining train motion without slipping tractive effort F should be less than or at the most equal to µW where µ the coefficient of adhesion between the wheel is and the track and W is the weight of the train on the driving axles (called the adhesive weight).