Re: super series wheelslip control

["Rod [comtrain]" <freight_man@hotmail.com>]

The Engineman's manual: March 1984
Operating Instructions A.N. BL Class Diesel Electric Locomotive
JT26C-2 Super Series
2237 kw (3000 hp)
speed at continuous rating 18.4 kph (11 mph)
255 - 900 rpm
gear ratio 62:15 [115kph (70 mph)]
CLYDE Engineering [EMD licencee]
Super Series System-Wheel Control System

The starting wheel slip system consists of electronic circuits separate from
the super series wheel control system.
The starting wheel slip system provides a backup for the Super Series System
in the event of Super Series failure. If all conditions are present, for
Super Series Operation, the Locomotive will automatically switch into Super
Series Operation.
(now this is ambiguous, not really indicating which is right, but we WERE
taught it happens from a stand)

The starting wheel slip system is a modified rate of change corrective type
system.
It reacts to the severity of the wheel slip by smoothly reducing power and
applying sand. Depending on the severity of the slipping condition, the
wheel slip may, or may not flash on and off as the slip is corrected. This
system is an improvement over past corrective type wheel slip systems.
However  it is not as sophisticated as the Super Series System.
( The paragraph above was never properly pointed out to us, I assumed that
IDAC was fitted, to replace the Super Series, should it fail. In fact this
system is much more sophisticated than IDAC, and more nearly like the Super
Series system, and so as an operator, I may have been confused by this
improved system, and yet.....)
The Super Series system is not a corrective type wheel slip system. It is a
wheel control system which allows each traction motor to seek maximum
tractive effort. In some cases this involves allowing the wheels to creep
[rotate at a speed slightly faster than ground speed] whilst still being
controlled.. Under severe rail conditions sand will be applied
automatically, along with smooth power control. The wheel slip light will
not come on during Super Series wheel control.
speed
> The radar system is not as reliable in everyday operation as you might
> think.  The speed information it provides drops out frequently, even in
> what could be termed normal conditions.  The system is designed to
> tolerate intermittent signal loss, but in weather extreme conditions,
> the dropouts can be long enough that Super Series has to resort to a
> stand-by system. When I said the system is occasionally confused, it
> meant in extreme weather conditions such as when there is standing water
> between the rails, not just that the ballast is wet, when there is
> torrential rain or heavy snow, or when there is a layer of solid ice on
> top of the ballast.  The system will even lose the speed reference over
> high trestles where the radar signal will just pass through the sleepers
> and not bounce back to the radar head.  It does not happen that often,
> but understanding that it can happen on occasion can help explain the
> occasional performance problems.


James, most of these problems are not applicable where I drive trains. It is
possible that you are right, but the Engineman that first asked this
Question, needed information, from a drivers perspective. I can tell you
that I have been operating Equipment fitted wheel creep since the early
80's, and our Instructors told us the way I explained it. And my experience
with this equipment definitely backs up our Instructions. If drop outs
occur, but the system is designed to ignore them, well what the heck, it
works, and I do not stall. As I said before, only time it did not work,
because I got some debris under the front that destroyed the Equipment.




> > I should also add that whilst the wheel creep is operating, you cannot
sand
> > the rails. Locomotives so equiped, sand automatically, and more
precisely
> > than the human foot.
>
> Unless the 81s are set up differenly than other EMD locomotives, manual
> sanding is typically locked out above a certain speed, usually about 12
> or 15 km/hr, but the system will allow manual sanding at lower speeds,
> even while the wheels are creeping.  The system will automatically sand,
> when necessary, above the lock-out speed, but manual sanding will be
> inoperative.
>
> > at higher speeds, the wheel creep cuts out, and wheel slip controlls
> > are more conventional, and again you regain use of the sander.

The Engineman's manual:
Manual Sanding
The Driver has control of manual sanding up to 5 km per hour, then Super
Series takes control.
Sanding returns to the Drivers Control when wheel Creep cuts out.

WE were told that wheel creep is what got heavy trains moving, and was
usefull up to about 20 kph

I never noticed the low speed sanding, and note that nowhere does the manual
mention upper speed of wheel creep. I have noted the squeeling wheels at up
to 40 kph, but generally, it seemed to complete below 20 kph.




>
> It is actually the reverse.  Super Series is cut out below about 7
> km/hr, since the doppler radar will not provide a reliable speed signal
> at lower speeds.  Wheel slip control is handled by a back-up system at
> these lower speeds that is similar to older wheel slip systems.  The
> older system is less likely to sustain wheel creep than the Super Series
> system, so tractive effort may not be as high at these lower speeds.  At
> higher speed, Super Series will continue to function, and will allow
> wheel creep if the conditions are right. I have seen sustained wheel
> creep at speeds in excess of 80 km/hr. However, since the locomotive's
> horsepower limits tractive effort at higher speeds, sustained wheel
> creep is less likely than when making a heavy pull up a steep gradient
> at 15 or 20 km/hr, when tractive effort and adhesion demand can be the
> highest.

The Engineman's manual:

Notable Features of Super Series Control
A.Within preset limits all wheels are allowed to creep to develop the
required tractive effort
B: To obtain an absolute reference of locomotive speed a RADAR unit is
fitted below the "A" (No.1) cab to check speed relative to the track bed.
C: Once wheels reach the preset limit of creep, the system starts to reduce
generator excitation to prevent motors 'running away", a situation which can
lead to damaged motors.
D: The system monitors the tractive efforts and adjusts generator field
currents to maintain MAXIMUM possible tractive effort at all times.

Cheers
Rod