This document discusses requirements for an ideal electric traction system for trains, including high starting tractive effort, low track wear, ability to handle temporary overloads, easy speed control, and being pollution-free and cost-effective. It also covers speed-time curves for different train services, types of train speeds, the mechanism of train movement, factors that affect energy consumption, and features of common traction motors like DC series motors and three-phase induction motors.

1. ELECTRIC TRACTION

2. Requirements of an ideal traction
system
 The starting tractive effort should be high so as to have
rapid acceleration.
 The wear on the track should be minimum.
 The equipments should be capable of withstanding
large temporary loads.
 Speed control should be easy.
 Pollution free.
 Low initial and maintenance cost.
 The locomotive should be self contain and able to run
on any route.

3. Speed time curve for train
movement

4. Typical speed time curves for different
services
 Urban or city services

5. Typical speed time curves for different
services
 Sub urban services

6. Typical speed time curves for different
services
 Main line services

7. TYPES OF SPEED IN TRACTION
 crest speed: Maximum speed
 Average speed:
 Schedule speed:

8. Mechanism of train movement
 Armature of driving motor has a pinion of
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

9. Specific energy consumption
 Energy input to the motors is energy consumption of
the train, since it is energy consumed for propelling
the train
 Energy consumption can be expressed in
watt-hr/tonne-km

10. Factors affecting energy consumption
 Distance between the stops.
 Train resistance
 Acceleration and retardation.
 Gradient
 train equipment.

11. Traction motors
 DC series motor
 Ac series motor
 Three phase induction motor

12. Traction motor electrical features
 High starting torque
 Simple speed control
 Regenerative braking
 Better commutation
 Capability of withstanding voltage fluctuations.
MECHANICAL FEATURES
 Light in weight.
 Small space requirement.
 Robust and should be able to withstand vibration.