Electric Traction System - Tractive Effort, Specific Energy Consumption, Coefficient of Adhesion

1. ELECTRIC TRACTION
- Mr. V. S. Wadkar

2. TOPICS TO BE DISCUSSED
• Tractive Effort
• Specific Energy Output
• Specific Energy Consumption
• Factors affecting Specific Energy
Consumption
• Coefficient of Adhesion

3. Tractive Effort
• Tractive Efffort – force developed by traction
unit at the wheel for moving traction unit.
• Tractive effort for acceleration:
Fa = 28.3 We.α kg
• Tractive effort required to balance the
gravitational pull:
Fg = W.G kg

4. Tractive Effort
• Tractive effort to overcome train resistance:
Fr = r.W kg
• Tractive effort to overcome curve resistance:
Fc = 0.4 c.W kg
• Total tractive effort:
Ft = Fa + Fg + Fr + Fc
Ft = 277.8 We.α ± 9.81 W.G + 9.81 W(r+0.4 c)
Newtons

5. Specific Energy Consumption
• Specific Energy Consumption – energy
consumed
• Specific Energy Consumption is ratio of
specific energy output at driving wheels to the
overall efficiency of transmission gear and
motor

6. Specific Energy Output
• Specific energy output
= Total energy output of driving axels
Weight of train x Distance covered by train
• Total energy output of driving axels
= Energy output of driving axels to accelerate
train (Ea) + Energy output of driving axels to
overcome gradient (Eg)+ Energy output of
driving axels to overcome friction (Er)

7. Factors affecting Specific
Energy Consumption
• Acceleration and retardation
• Gradient
• Distance between the stops
• Train resistance
• Train equipment

8. Coefficient of Adhesion (μa)
• F α W
• F = μa.W Newtons
• F = 9.81 x 1000 μa Tonne
Factors affecting Coefficient of Adhesion:
• Track
• Mechanical Parts
• Electrical Parts