Subway Braking System

Sequence Of Operation:

  • The braking systems on many subway and rapid-transit cars made use of electromagnetic induction and eddy currents.
  • An electromagnet attached to the train is positioned near to the steel rails.
  • When a large current is passed through the electromagnet, a strong magnetic field is set up near the rails.
  • The relative motion of the rails and the electromagnet will induce eddy currents in the rails.
  • By Lenz’s law, these eddy currents will flow in a direction to oppose the changing flux.
  • Hence, there will be a retarding force on the train.
  • As the eddy currents decreases steadily in magnitude as the train slows down, the braking effect feels smooth to the passenger.


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