Dan Noël's Experience in Traction

Up till the early 1980's, Dan was a railroad aficionado, spending school vacations accumulating a wealth of theoretical and field knowledge on the infrastructure, the rolling stock and the operation of railroads, learning from his father's professional experience as a fleet manager at the Belgian National Railroad

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Railroads are a world of their own, a thorough introduction to which deserves a book. Within the scope of this web, suffice to list a few aspects of traction applications that challenge motor drives:

  • Technical challenges:
    • Relative high power: 1 MW as an order of magnitude
    • High nominal input voltages: 3 kV DC is common
    • Inertia of motor load varies considerably: extremely high when pulling a heavy freight train on a plain, extremely low during wheel slip
    • High torque requirement when stopped, as heavy freight trains require some extra effort to start moving
    • Wheel slip condition to be detected and cleared promptly, if possible in the bud; provokes mechanical shocks and can wear out rails
    • Ability for driver to finely adjust the torque in order to avoid shocks in the train, which can annoy passengers and break couplers
    • Unusual space and mass constraints
    • Speed differentials induced by uneven wheel wear
    • Need for redundancy: provision to isolate failed motor or converter in the field, sometimes without stopping the train
    • Risk of unstable interaction between onboard converters, catenary and substations
    • High power single phase systems, some of them at low frequency
    • Short-circuit protection to take into account the variable position of the loads and their intermittent connection of normally disconnected circuits
    • Non-symmetrical and harmonic loads on power systems
    • Dynamic brake (i.e. turning traction motors into generators to brake the train) is used often and over long periods of time
    • EMC: excessive harmonic rejection may disturb railroad signaling systems (risking collisions) and third-party equipment
    • Extreme environmental stress: temperature, humidity, dirt and pollution (including human), shocks and vibrations...
  • Reliability and maintenance challenges:
    • High reliability: a train stopped because of traction system failure can obstruct a railroad for hours, wreaking havoc on schedules
    • Long maintenance intervals and easy maintenance

Before graduating, Dan noticed flaws in the design of the drives of the first chopper-driven electric locomotives in the world, some of which were confirmed in the field.

Dan got much knowledge on the operation of electric and diesel-electric locomotives with traditional electromechanical controls, pointing to a flaw in an upgrade by the Belgian National Railroads before it caused a field failure.