New SCT locomotives

 
  nic Chief Train Controller

Location: Brisbane, QLD
Aww well that settles it i guess. Looks like they'll be a hood unit

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  Shacks Ghanzel

Location: Sir Big Lens of the Distant Upper Hunter
So a black, red and white V/Q/FQ with slightly different guts.
  nutbagg Deputy Commissioner

Location: Back at the chocolate factory.
So a black, red and white V/Q/FQ with slightly different guts.
"Shacks"
Massive difference only common bits will be 710 donk and Epic airbrake; most of the loco is of new design such as bogies, frame etc.
  Duncs Chief Commissioner

Will the fact that it is AC traction and not DC traction reduce its top speed?
As these locos usually do 110kph across the nullabor plain.
  simonl Chief Commissioner

Location: Brisbane
Will the fact that it is AC traction and not DC traction reduce its top speed?
As these locos usually do 110kph across the nullabor plain.
"Duncs"

Wouldn't think so - otherwise where would the advantage of AC traction be?  I'd like to see them do even more speed, and on the Nullabour there doesn't seem any reason to restrict it other than track strength.
  Duncs Chief Commissioner

Will the fact that it is AC traction and not DC traction reduce its top speed?
As these locos usually do 110kph across the nullabor plain.
"Duncs"

Wouldn't think so - otherwise where would the advantage of AC traction be?  I'd like to see them do even more speed, and on the Nullabour there doesn't seem any reason to restrict it other than track strength.
"simonl"


BTW What is the track strength out there?
  Shacks Ghanzel

Location: Sir Big Lens of the Distant Upper Hunter
Can someone correct me if I am wrong.

A DC loco has AC output from the generator that runs through a rectifyer to change it to DC ?
A AC loco does not require the rectifyers, therefor saving weight ?
  tery84_trainee Assistant Commissioner

yep prety corect except so,e of the older loco's like vic t's s's y's wich are fitted with main generators put out dc power
  derekmorton Chief Train Controller

Location: DVR Eltham, Vic
A AC loco does not require the rectifyers, therefor saving weight ?[/quote]

Incorrrect, the Ac and DC loco's have alternators and rectifiers.

In the dc varient the dc is fed directly to the dc control system.

In the ac variant, the dc is fed to the inverter bank, which generates the required variable frequency AC required to operate the AC traction motors.
  simonl Chief Commissioner

Location: Brisbane
Will the fact that it is AC traction and not DC traction reduce its top speed?
As these locos usually do 110kph across the nullabor plain.
"Duncs"

Wouldn't think so - otherwise where would the advantage of AC traction be?  I'd like to see them do even more speed, and on the Nullabour there doesn't seem any reason to restrict it other than track strength.
"simonl"


BTW What is the track strength out there?
"Duncs"

I understand it is over 90% concrete sleepered, and I don't know if there's too much light rail, but I think the ballast is a limitation.


AC traction allows maximum power to be applied over a broader speed range.  That's it's advantage.  As to why, I'm not quite sure.  Apparently it would add weight (about 3t) to an NR to upgrade to AC traction.
  derekmorton Chief Train Controller

Location: DVR Eltham, Vic
>AC traction allows maximum power to be applied over a broader speed range. That's it's advantage.

No that is not so.

AC's advantage is that it produces more torque for the applied power.
AC is also far more accurate in the speed control of the motors / wheels.

Maximum grip is available at 11% slip, the AC control system is able to apply this 11% slip very accurately.

Derek
  Dog Spike Train Controller

Location: Melbourne
If an NR was AC, the AC out as AC, rectified to DC then back to AC again. The ripple in the AC is more controlled that way for the motor control. And it would add alot more than 3t to an NR.
  Shacks Ghanzel

Location: Sir Big Lens of the Distant Upper Hunter
Why not just run straight out AC ?
The power companies don't change it to DC then back again.
  derekmorton Chief Train Controller

Location: DVR Eltham, Vic
Why not just run straight out AC ?
The power companies don't change it to DC then back again.
"Shacks"


You can't run straight AC on a loco, you don't have any speed control.
Mains AC motors run on a 3 phase rotating field and its at 50HZ.
  M636C Minister for Railways

Why not just run straight out AC ?
The power companies don't change it to DC then back again.
"Shacks"


You can't run straight AC on a loco, you don't have any speed control.
Mains AC motors run on a 3 phase rotating field and its at 50HZ.
"derekmorton"


My understanding is that for long underwater cables, power companies do change to DC and back again. That is related to reducing the different kinds of power losses incurred in very long transmission lines.

The power developed from a locomotive alternator is already three phase AC, and the frequency varies according to the diesel engine speed.

The traction motors, however, have to be supplied with AC power that allows the frequency to vary down to close to zero, since the frequency  controls the speed of the traction motor.

The only way of obtaining this result is to convert the power to DC and then feed it through an inverter (technically an "Insulated Gate Bipolar Transistor") which allows you to match the alternating current frequency and the voltage to that required by the motor. The required voltage and current is obtained by combining the IGBT elements in groups in series and parallel.

M636C
  nutbagg Deputy Commissioner

Location: Back at the chocolate factory.
Why not just run straight out AC ?
The power companies don't change it to DC then back again.
"Shacks"
An AC motor's speed is dependent on the frequency of the voltage applied to it. Domestic supply is always 50Hz so power station generators always run at a constant speed.
  derekmorton Chief Train Controller

Location: DVR Eltham, Vic
>My understanding is that for long underwater cables, power companies do change to DC and back again. That is related to reducing the different kinds of power losses incurred in very long transmission lines.

NO, power companies only deal with AC, however HIGH voltage AC is what gives the low transmission losses.  500KV is used in Victoria from the Latrobe Valley to Portland for the aluminium smelter.
  M636C Minister for Railways

>My understanding is that for long underwater cables, power companies do change to DC and back again. That is related to reducing the different kinds of power losses incurred in very long transmission lines.

NO, power companies only deal with AC, however HIGH voltage AC is what gives the low transmission losses.  500KV is used in Victoria from the Latrobe Valley to Portland for the aluminium smelter.
"derekmorton"


If I were you I would check some references before saying that DC is not used on long underwater transmission lines.

Check details of a link between Victoria and Tasmania.

I concur that it isn't used in even very long lines over land.

M636C
  simonl Chief Commissioner

Location: Brisbane
>AC traction allows maximum power to be applied over a broader speed range. That's it's advantage.

No that is not so.

AC's advantage is that it produces more torque for the applied power.
AC is also far more accurate in the speed control of the motors / wheels.

Maximum grip is available at 11% slip, the AC control system is able to apply this 11% slip very accurately.

Derek
"derekmorton"

Actually, Power (Watts) = Torque (Newton-Metres) x Rotational speed (radians/s).

So it is so. But tks for explaining why it is so.
  simonl Chief Commissioner

Location: Brisbane
If an NR was AC, the AC out as AC, rectified to DC then back to AC again. The ripple in the AC is more controlled that way for the motor control. And it would add alot more than 3t to an NR.
"Dog Spike"

That was the figure I remember reading.  Do you have better information?  It seems to me that 3t is a lot for DC-AC rectifiers and some electronic control.
  derekmorton Chief Train Controller

Location: DVR Eltham, Vic
>If I were you I would check some references before saying that DC is not used on long underwater transmission lines.

>Check details of a link between Victoria and Tasmania.

You are the only one mentioning underwater transmission, and yes taslink is 400KV DC, but only as its under water.

My comments apply to above water transmission, which is what has been discussed.
  bluebird252 Assistant Commissioner

what class are these locos going to be named  SCT class ? would there be a possiblity that the sole V class would join this class allowing 2 Gs to go back to Pac Nat ? I know which loco i would prefer because the V wasnt it mainly used on the SCT services and was mainly built for this service?
  wongm GEEWONG

Location: Geelong, Victoria
would there be a possiblity that the sole V class would join this class allowing 2 Gs to go back to Pac Nat ? I know which loco i would prefer because the V wasnt it mainly used on the SCT services and was mainly built for this service?
"bluebird252"
The V class was purchased as a replacement for a pair of G class locos written off in an accident, and was purchased with the insurance money.
  brads Train Controller

Location: Werribee, Victoria
would there be a possiblity that the sole V class would join this class allowing 2 Gs to go back to Pac Nat ? I know which loco i would prefer because the V wasnt it mainly used on the SCT services and was mainly built for this service?
"bluebird252"
The V class was purchased as a replacement for a pair of G class locos written off in an accident, and was purchased with the insurance money.
"wongm"

Does anyone know if the V class will stay in R&B duties or would it be transfered to banking duties in intermodal.
Regards
brads Very Happy
  simonl Chief Commissioner

Location: Brisbane
Banking duties in intermodal?  Never heard of it.  Where does this apply?

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