electric traction basics

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.