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Re: Recent derailments - Metro North
Author: Dr Zarkoff
Date: 12-05-2013 - 14:37
>Dr. Zarkoff wrote : "Regenerative braking won't work if there is no load elsewhere on the [trolley] wire or 3rd rail."
>If this is true, how was Milwaukee Road able to use regenerative braking on its' Lines West electric locomotives ???
Regenerative braking, whether true regenerative or dynamics on a diesel, must be able to dissipate the train's kinetic energy or it will be ineffective. With [diesel] dynamics, this is accomplished by the resistor grids on each locomotive. With electrics, like the VGN and MILW, there were no grids on the locomotives, so the power was fed back into the trolley wire. On both, this power was used to power uphill trains. If there was insufficient uphill train load, the VGN dissipated the excess power with liquid rheostats at the power house (I suspect the N&W did the same -- PRR locomotives weren't equipped for regeneration, with the possible exception of Big Liz). The MILW either powered uphill trains or sold the power back to the power company.
For all these railroads, if there was no [other] electrical load on the trolley wire, regeneration wouldn't work because there would be no way to dissipate the electricity generated by the kinetic energy of the train. IOW, whenever the MILW's power companies couldn't absorb the regenerated power, the MILW couldn't regenerate beyond powering an uphill train, and if there was no uphill train, then there would be no regeneration at all. This undoubtedly happened from time to time.
> other trains nearby, the Electric Useage meters in the substation would actually run backwards,
This may have been the case at the beginning, but for later years it's an urban legend. There was a second meter which ran up credit. I asked a substation operator about this, and he showed me the two meters, which were side by side on the electrical panel.
> Is it indeed possible for electric current to run through a substation in either direction ???
If the substation has rotating conversion equipment (M-G sets, rotary converters), the process is essentially bi-directional depending upon load, although some additional controlling apparatus (control relays etc.) is necessary. Solid state conversion equipment is another matter.
>If this is true, how was Milwaukee Road able to use regenerative braking on its' Lines West electric locomotives ???
Regenerative braking, whether true regenerative or dynamics on a diesel, must be able to dissipate the train's kinetic energy or it will be ineffective. With [diesel] dynamics, this is accomplished by the resistor grids on each locomotive. With electrics, like the VGN and MILW, there were no grids on the locomotives, so the power was fed back into the trolley wire. On both, this power was used to power uphill trains. If there was insufficient uphill train load, the VGN dissipated the excess power with liquid rheostats at the power house (I suspect the N&W did the same -- PRR locomotives weren't equipped for regeneration, with the possible exception of Big Liz). The MILW either powered uphill trains or sold the power back to the power company.
For all these railroads, if there was no [other] electrical load on the trolley wire, regeneration wouldn't work because there would be no way to dissipate the electricity generated by the kinetic energy of the train. IOW, whenever the MILW's power companies couldn't absorb the regenerated power, the MILW couldn't regenerate beyond powering an uphill train, and if there was no uphill train, then there would be no regeneration at all. This undoubtedly happened from time to time.
> other trains nearby, the Electric Useage meters in the substation would actually run backwards,
This may have been the case at the beginning, but for later years it's an urban legend. There was a second meter which ran up credit. I asked a substation operator about this, and he showed me the two meters, which were side by side on the electrical panel.
> Is it indeed possible for electric current to run through a substation in either direction ???
If the substation has rotating conversion equipment (M-G sets, rotary converters), the process is essentially bi-directional depending upon load, although some additional controlling apparatus (control relays etc.) is necessary. Solid state conversion equipment is another matter.
