Millennium Line - Evergreen Extension | Completed

[aberdeen5698]

Originally Posted by jsbertram

Since the LIM requires electricity to generate the magnetic fields to move the train, when there is no LIM power there would therefore be no magnetism in the LIM for propulsion, nor for LIM braking.

It is possible for the LIM motor to brake the train using no external power - see this paper, which states:

Since the generated electric power can be allotted to the armature copper loss, an on-board energy source becomes unnecessary to maintain excitation of the LIM.

The issue would whether or not the vehicle control systems could maintain excitation of the LIM coils during the transition from powered to unpowered mode.

Originally Posted by jsbertram

Loss of power should cause the train to go into Emergency Braking...

I think we all understand that the system uses conventional wheel-based braking for emergencies and when stationary. The issue being discussed was the advantage of LIM braking on steep grades in inclement conditions because it doesn't rely on wheel adhesion, and whether or not that advantage was negated by the need to maintain separations based on worst-case scenarios (i.e., power loss).

[adrianroam95]

Found this video on YouTube:

• Video Link

Almost there!

[MIPS]

Originally Posted by aberdeen5698

The issue being discussed was the advantage of LIM braking on steep grades in inclement conditions because it doesn't rely on wheel adhesion, and whether or not that advantage was negated by the need to maintain separations based on worst-case scenarios (i.e., power loss).

Mk I's and II's have a hydraulic disc brake for keeping trains stationary under normal conditions but also have an independent magnetic track brake which operates off a battery supply and will hold the train in emergencies. They are tested automatically when a train enters Edmonds station.

[DKaz]

Originally Posted by MIPS

Mk I's and II's have a hydraulic disc brake for keeping trains stationary under normal conditions but also have an independent magnetic track brake which operates off a battery supply and will hold the train in emergencies. They are tested automatically when a train enters Edmonds station.

And 20 years later, I finally get an explanation as to what that sound is. Thanks!

[jsbertram]

Originally Posted by aberdeen5698

It is possible for the LIM motor to brake the train using no external power - see this paper, which states:
The issue would whether or not the vehicle control systems could maintain excitation of the LIM coils during the transition from powered to unpowered mode.

I think we all understand that the system uses conventional wheel-based braking for emergencies and when stationary. The issue being discussed was the advantage of LIM braking on steep grades in inclement conditions because it doesn't rely on wheel adhesion, and whether or not that advantage was negated by the need to maintain separations based on worst-case scenarios (i.e., power loss).

However, my message was in response to the belief that "Skytrain can use the LIM to brake even during power outages. "

No power to the LIM, therefore no magnetic fields on the LIM, therefore no means for the LIM to do braking (or propulsion) when the power is off.

[aberdeen5698]

Originally Posted by jsbertram

No power to the LIM, therefore no magnetic fields on the LIM, therefore no means for the LIM to do braking (or propulsion) when the power is off.

The LIM can brake without power, as long as the train is moving and excitation in the coils can be maintained when the train looses power. Eddy currents in the stationary reaction rail interact with the energized coil to generate LIM power from the kinetic energy of the train.

I don't know whether or not the LIMs in our Skytrain cars can do this, but it is certainly possible in principle, as indicated in the paper I linked to.

[dpogue]

Originally Posted by DKaz

And 20 years later, I finally get an explanation as to what that sound is. Thanks!

There was a (slightly) more details explanation in the comments on the Buzzer blog at one point: http://buzzer.translink.ca/2010/02/the-night-shift-on-the-skytrain-guideway/#comment-47806

[jsbertram]

Originally Posted by aberdeen5698

It is possible for the LIM motor to brake the train using no external power - see this paper, which states:
The issue would whether or not the vehicle control systems could maintain excitation of the LIM coils during the transition from powered to unpowered mode.

I think we all understand that the system uses conventional wheel-based braking for emergencies and when stationary. The issue being discussed was the advantage of LIM braking on steep grades in inclement conditions because it doesn't rely on wheel adhesion, and whether or not that advantage was negated by the need to maintain separations based on worst-case scenarios (i.e., power loss).

Unfortunately, the link is only to the first page of the paper, but I can see they are proposing a LIM braking system to be added to the bogie that uses a typical traction motor for propulsion. This is not how the Bombardier (Expo and Millennium line) trains operate, but is how the Rotem (Canada Line) trains get their propulsion.

Their proposed LIM operates against the track-rail itself to induce eddy current braking. The power for this is actually derived from the traction motor (acting as a generator). Since the Bombardier trains don't use traction motors, this concept can't be implemented on the Bombardier trains.

However, because the Rotem trains use conventional traction motors, this could be added to their trains. The issue then becomes: is this better than the conventional braking systems already in use?

Even if this can be proven useful, a conventional braking system will still be be needed once the train is halted (since the traction motor -acting as a generator- is no longer supplying power to the LIM for braking.


I also notice that in Fig. 2, they are using a velocity of 160 KM/Hr which is significantly faster than what can be achieved by the Skytrain cars. I think this LIM braking system concept was intended for their high-speed MagLev train systems in Japan, or other high-speed trains where use of conventional braking systems at high speeds would be problematic, and an auxiliary braking system like this LIM is desired.


It's an interesting concept, but I can't see how it would be used on the Skytrain system here.

[aberdeen5698]

Originally Posted by jsbertram

Their proposed LIM operates against the track-rail itself to induce eddy current braking. The power for this is actually derived from the traction motor (acting as a generator).

Apparently you missed the part that I quoted: "Since the generated electric power can be allotted to the armature copper loss, an on-board energy source becomes unnecessary to maintain excitation of the LIM".

You need power to energize the LIM coils to "bootstrap" the process, but once that's done it's self-sustaining as long as the train is moving. Since the cars already have on-board batteries to power the magnetic brakes, it seems feasible that these could be used to activate the LIM even if coil energization couldn't be sustained when external power is lost.

The issue then becomes: is this better than the conventional braking systems already in use?

Yes, that is the issue (aside from whether or not our vehicles are actually capable of this). At worst, it could at least assist the conventional braking systems, therefore resulting in shorter stopping distances even on steep grades in conditions with poor rail adhesion.

[Alex Mackinnon]

Originally Posted by aberdeen5698

The LIM can brake without power, as long as the train is moving and excitation in the coils can be maintained when the train looses power. Eddy currents in the stationary reaction rail interact with the energized coil to generate LIM power from the kinetic energy of the train.

I don't know whether or not the LIMs in our Skytrain cars can do this, but it is certainly possible in principle, as indicated in the paper I linked to.

A better question is what cases can this actually be fully disabled. If the answer is yes to any system or set of systems failing, then you can bet that the disc brakes are the final spec because they're failsafe. They have to be held in the off position, so if power/pressure/control is lost they kick on. If the magnetic system doesn't failsafe then it's probably not used to determine the maximum grade spec.

If somehow the entire train's power and control system were disabled in one stroke, could you count on the LIM or Mag Brake to stop the train?

[aberdeen5698]

Originally Posted by Alex Mackinnon

If somehow the entire train's power and control system were disabled in one stroke, could you count on the LIM or Mag Brake to stop the train?

I have no idea as currently implemented. If it were necessary, though, I'm sure the control systems could be made redundant enough to rely on. Twin engine airliners that meet certain reliability standards are allowed to fly beyond 90 minutes out over water, and their systems are far more complex.

This is all hypothetical, of course.

[queetz@home]

Back to the actual topic of the thread which people love to deviate from....

Originally Posted by adrianroam95

Found this video on YouTube:

• Video Link

Almost there!

Thanks for the video adrianroam95! Looks pretty cool.

One thing that bugs me though....currently (as of this afternoon), the gantry crane is above a segment just north of Austin Avenue. The segment is not 100% complete, one piece of the segment at the south end is still not connected. It has been like that since Wednesday morning...and its already Friday.

So close and yet so far....I wonder why it seems work has stopped....

[GeeCee]

Posted on the Evergreen Line Facebook page today:

http://i.imgur.com/euSy4Kl.jpg

[Meraki]

Originally Posted by GeeCee

Posted on the Evergreen Line Facebook page today:

http://i.imgur.com/euSy4Kl.jpg

Great photo! Hopefully they correct that left turn signal in the middle of the photo.

[officedweller]

Webcam pics from today:

Port Moody Station - I wonder why the tracks separate so far west of the storage track?





Inlet Centre Station - you can see the elevated section near Klahanie in the background:

[SpongeG]

what are they gonna do around the columns along north road? just put up cement block things like they have along some stretches of lougheed hwy? or will they do something fancier?

[queetz@home]

Originally Posted by SpongeG

what are they gonna do around the columns along north road? just put up cement block things like they have along some stretches of lougheed hwy? or will they do something fancier?

If people stopped deviating to useless discussions that shouldn't really be brought up and extensively debated in this thread, you would have not missed the answer to this very question which was posted by officedweller VERY RECENTLY....

Originally Posted by officedweller

Webcam pics from today:

Port Moody Station - I wonder why the tracks separate so far west of the storage track?

I wonder about that too. Seems like a waste of space...

[Millennium2002]

I'm just taking a long shot, but it looks mighty appetizing to fly the Murray-Clarke connector over that section in the future...

EDIT: Wait, this section is a little further than where I'd normally think the overpass would go...

[officedweller]

Similarly, I was wondering if it was to allow columns to be erected in between in future - but for what I don't know. Waterfront access?

[officedweller]

Originally Posted by finalcoolman

No they are the L shaped columns to make room for the curving roadway underneath, like the ones on North Rd to make way for the left turn bays underneath.

Yup - there they are.
(It does seem a bit odd though, given that there appears to lots of space
around to design a road without them (but I guess it's minimizing the need to rebuild the existing curved road).


http://wcs.pbaeng.com/projects/R1_Transit