What current type is used by the overhead traction system after conversion at substations?

What current type is used by the overhead traction system after conversion at substations?

• A. Alternating current (AC)
• B. Direct current (DC)
• C. Pulsed current
• D. Three-phase current

Answer: (B)

Direct current is used by the overhead traction system after conversion at substations. Electric power comes from the grid as alternating current, and substations convert it to direct current before feeding the overhead lines. This DC power is what powers the traction motors on trains, and it allows straightforward, controllable motor operation—providing strong starting torque and smooth speed control, which is ideal for moving heavy trains. The other options describe forms of current that aren’t what the overhead system carries once conversion has occurred: AC is what the grid provides before conversion, three-phase current is another form of AC used in different contexts, and pulsed current isn’t the standard traction supply on the overhead line.

Direct current is used by the overhead traction system after conversion at substations. Electric power comes from the grid as alternating current, and substations convert it to direct current before feeding the overhead lines. This DC power is what powers the traction motors on trains, and it allows straightforward, controllable motor operation—providing strong starting torque and smooth speed control, which is ideal for moving heavy trains. The other options describe forms of current that aren’t what the overhead system carries once conversion has occurred: AC is what the grid provides before conversion, three-phase current is another form of AC used in different contexts, and pulsed current isn’t the standard traction supply on the overhead line.