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25 kV AC power supplies

  • 29-05-2021 5:48pm
    #1
    Victor
    Registered Users, Registered Users 2 Posts: 78,474 ✭✭✭✭


    So, the overhead line provides 25 kV AC to the on-train transformer. What voltage (typically) does the transformer supply to the motors?


Comments

  • #2
    GerardKeating
    Registered Users, Registered Users 2 Posts: 7,697 ✭✭✭GerardKeating


    Victor wrote: »
    So, the overhead line provides 25 kV AC to the on-train transformer. What voltage (typically) does the transformer supply to the motors?

    I thought the DART was 1,500 V DC...


  • #3
    Victor
    Registered Users, Registered Users 2 Posts: 78,474 ✭✭✭✭Victor


    GerardKeating wrote: »
    I thought the DART was 1,500 V DC...

    It is. Internationally, 25 kV AC is quit common for long distance services, as it means fewer lineside substations.


  • #4
    tabbey
    Registered Users, Registered Users 2 Posts: 1,943 ✭✭✭tabbey


    Victor wrote: »
    So, the overhead line provides 25 kV AC to the on-train transformer. What voltage (typically) does the transformer supply to the motors?

    Difficult to find the answer.
    Looking at numerous technical details in books and magazines, the power in hp/KW is often given, and sometimes the make and model number but the voltage remains elusive.
    I R R S journal, October 1984, has two articles on the electrification project, one by R P Grainger, CME, informs us that the traction motors on the 8100/8300 sets are as follows:
    Four (per power car), nose suspended, self ventilated.
    Traction motor rating: 130 KW (337v, 440a, 70 per cent field).
    This suggests that these motors run on 337 volt but perhaps only at 70% field, so maybe at 100% the full voltage of the motor could be 480 volt.
    It's reasonable to suppose that DC motors in ac locos and emus could be similar. Since the 1980s, a growing number of AC electric locos and railcars have AC motors, as the moving parts of DC motors are more likely to fail.
    AC locos with DC motors, would need a rectifier as well as a transformer. Mercury arc rectifiers were used until the 1960s when they were replaced by silicon.


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