Electric Traction System

Electric Traction

• Electric traction is a locomotion method where the driving force is obtained from electric motors.
• Electric traction is a practical application of electricity in everyday life, used in transportation, such as electric trains, trolley buses, tramcars, and diesel-electric and gas turbine electric vehicles.

Ideal Traction System

• An ideal traction system should have the following characteristics:
• High starting tractive effort for rapid acceleration
• Self-contained and compact locomotive or train units
• Equipment capable of withstanding large temporary overloads
• Minimum wear on the track
• Braking system that causes minimum wear on the brake shoes and regenerates energy back to the supply during braking
• Minimum equipment required with high efficiency and low initial and maintenance cost
• No interference with communication lines
• Easy speed control

Systems of Electric Traction

• There are two main groups of electric traction systems:
• Units that receive electric power from a distributing network at suitable points (e.g. trolley buses, tramways, and railways)
• Self-contained locomotives that generate their own power (e.g. diesel-electric traction, ships, and petrol-electric trucks)

Advantages of Electric Traction

• Electric traction has several advantages over steam traction, including:
• Cleanliness: no smoke and flue gases
• Lower maintenance cost (50% of steam traction)
• Shorter starting time (no need to wait for hours like steam locomotives)
• Regenerative braking, which feeds back 80% of the energy required during ascent
• Lower maintenance cost of brake shoes, wheel treys, and rails
• Lower center of gravity, making it more stable and able to take curves at higher speeds
• Saving in high-grade coal, which is deficient in many countries
• Absence of unbalanced forces, resulting in a higher coefficient of adhesion
• Less noise
• Regenerative braking can be applied, returning power back to the supply

Disadvantages of Electric Traction

• Despite its advantages, electric traction has some disadvantages, including:
• High capital cost of the overall electric traction system
• Failure of power can cause disruption of traffic for several hours
• Interference with communication lines, which can be solved by removing them to a far-off place or using underground cables, making the system more expensive