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In the February issue, this column took on the questions and answers format to address some of the situations which I, along with you, the readers, had concerning events which they had happen, along with wanting to better understand how locomotive equipment reacts under both normal and not so normal operating conditions.
Today, I'll be going back with this style of approach, as I have received other inquiries and requests from you to outline what, how and why options in place on locomotives respond. I'll start off by answering a special request from an engineer who had a question which focuses on featuring the models of locomotives he works with on a daily basis; the SW15 and MP15 units used at the bowl yard facility (I am a fellow who does believe in all around coverage; to me, there is not any such animal as an unimportant question).
YARD SWITCHER LOCOMOTIVE SYSTEMS
Regardless of the type of service a locomotive will be primarily targeted for, a customer may request the type of options needed for fulfilling the specific needs and conditions for that category of service. In the instance of the SW15 and MP15 units operating at the bowl yard, there is an item in use which allows for adaptability to various situations. It is the Service Selector switch on the control stand. This switch is of the rotary snap type format, and it allows for selecting the type of requirement for the intended service.
The functions of the positions are:
ROAD (AUTO) - It is for use during moderate and high speed road operations. Should the
locomotive be involved in multiple unit operations with locomotives equipped for making
transition, it will allow for this change.
SERIES (FORESTALLING) - This position is used for whenever the locomotive is to be
involved in slow speed, drag type service. At this speed range, the desire for the unit to make
transition is more infrequent than it is for high speed operations, so this position keeps the main
generator to traction motors connections in the series mode.
SWITCHING 1 - This is the position normally used for yard switching. With it, you are provided
fast, but controlled throttle response for switching operations. In this position, the diesel engine
will run at low speed idle.
SWITCHING 2 - The difference in this position from the Switching 1 position is that the engine
will idle faster. This will produce the result of faster acceleration from the locomotive whenever
"kicking" cars is desired.
A DYNAMIC BRAKING SYSTEM FEATURE
The inquirer about this matter has at times asked me about where the dynamic brake is on these
locomotives. Well, here is an answer that may surprise most of you. To some extent, there is
dynamic braking equipment on some of the SW15's at the bowl. They are outfitted with the
magnet valve which provides the dynamic brake interlock protection (in this instance, it is the
Type 1 version found on many of the UP and SP locomotives).
This modification was a carryover of a program done to the SW10 home rebuilt switcher units of the UP; it was done because the locomotives were incurring flat spots from air brake applications during dynamic braking operations as they were being transported from one location to another.
The magnet valve is tied in with the No. 24 train line pin (the braking regulation control), and serves as a backup for preventing application of the air brakes during such operations. So as to not be misinterpreted: the use of the dynamic brake interlock on a locomotive DOES NOT relieve an engineer from compliance during dynamic braking operations of paragraph 2 of Air Brake rule 31.5.4 in the current UP Air Brake and Train Handling Rules.
THE PACESETTER CONTROL BOX
Now let's head up to the Crest yard, where an engineer on those jobs had a good question for me. It is about the pacesetter control box employed on the GP38-2 doubleheaders sets. To begin, it has in common with the dynamic braking system a tie in with the No. 24 train line pin, which is the one used for regulation of the desired output setting (the other pin used is the No. 1, which permits sending the setup command to the other MU connected units). Specifically, the inquiry deals with the functions of some switches and controls.
Well, let's take a closer look at them:
PLUG/MOTOR SWITCH - This toggle switch, when in the Motor position, permits
normal powering speed control for flat or uphill grade terrain. In the Plug position, the
locomotive must be operated with the reverser set opposite to the direction of movement.
The range switch is required to be set at the .1-1MPH position, along with the Auto-Man
switch in the Man position during the initial setup process. The Plug switch is used for
loading on a down hill grade.
LOAD/AXLE KNOB - This is used to set the Low-Medium-High position for train load
weight into the axle limitations so as to not overload the electrical systems in the traction
motors.
SPEED RANGE SWITCH - This switch allows for selecting the operating ranges of the
control box.
START/MANUAL CONTROL - This dial is used for starting the train or switching move
in the pacesetter control. In the Start position, traction motor current is regulated
automatically, and the manual position offers that control to the operator.
SD90/43AC Q & A
There were two questions submitted to me by engineers regarding events to have happened while operating as lead units the SD90/43AC locomotives. In the first case, the locomotive "fired" what is referred to as a hard crowbar; he also noted when this happened, the effect was worse than that of a ground relay tripping (this is very true; it is because you are producing much higher levels of voltage in the AC control systems than in the DC portions.
The sudden removal of this level of power produces this effect). Here is the background: This feature is part of what is named the Inverter Protection System (IPS); it is in the SIBAS16 inverter control system, and it is there to protect the system's components from potentially damaging electrical imbalances. The "firing" of a hard crowbar creates an authentic dead short across the DC Link switchgear; this action causes the main generator to stop producing output and, in addition, immediately discharges the DC Link voltages by way of placing on-line numerous devices called bleeder resistors, which reduce the voltage levels to little or no degrees.
Although in most cases, the condition(s) which caused the crowbar "firing" will be in the SIBAS16 system portions, it is also possible that a ground relay tripping in the DC portions components can trigger an AC system crowbar "firing".
So, for safety reasons, please make note of these conditions to expect when a hard crowbar "firing" occurs: If the crowbar is "fired" when the locomotive is under full load at low track speed, the sudden removal of power can cause pretty good jolt in the cab (the lower the speed, the more severe the jolt can be). So when in this type of an operating situation, it is a very good idea for cab occupants to remain seated. But if it does become necessary for you to stand or move about in the cab, make sure that you maintain a secure handhold.
After the unload from a crowbar "firing", the DC Link gear will be cycled for a period of 10 to 12 seconds; afterwards when the DC Link and main generator voltages have decayed to a safe level, the load output will gradually be returned to the level of the throttle setting (this process is the automatic reset of a crowbar "firing").
Should the locomotive then within a time period of three minutes "fire" two or more hard crowbars, the locomotive will drop out loading and lockout the electrical system. So in this case, the crowbar will have to be manually reset using the EM2000 display.
If the fault that caused the crowbar occurred with one of the two inverters, it may be
necessary for you to cutout the problem inverter. The Cutout soft key selection will be
displayed immediately on the setup menu display. Be sure that before you use the Cutout
key, that you have taken the locomotive "off the line". The locomotive will now produce
up to 55% of its power and dynamic braking effort whenever it is in Run 8 throttle or Full
8 dynamic braking handle position.
The other question concerned an engineer getting an EM2000 display screen message which said
TCC2 TORQUE REDUCTION: WHEEL DIAMETER MISMATCH. Specifically, what is this
telling you? Background: Wheel mismatch within a set of trucks is detected by the SIBAS16
inverter control computers. The data being used to calculate and process this information are:
A. The wheel speed from the traction motor probes.
B. The flux density from the AC current going to the traction motors.
If these items find that within a truck, you have over 3/10 of an inch in wheel variance, you will
get the torque reduction crew message display. What starts is you will get a warning light at a
66% mismatch, along with a crew message display of TCC WHEEL DIAMETER MISMATCH
WARNING. This will indicate there is a 2/10 of an inch wheel variance present, but it will not
result in a torque levels reduction. At 76% mismatch, you will start getting some torque
reduction. At 134% mismatch, the torque output will go to zero.
Whenever you start getting torque reduction, up to 10% power of the inverter for that truck is then "phase shifted" over to the other inverter, thereby raising the output of that truck to 55%. The full 10 % is dependent upon the rail adhesion conditions being there.
DP Q & A
Q. Why is it possible on the control box console to have an air flow readout of zero on a DP coal train? A. It is because of the gradient conditions you now have in effect. Along with the placement of the locomotives in the train, you are at those locations pumping air into the brake pipe. Due to this, you now have a more evenly charged brake pipe than what you would have if all the locomotives were placed on the head end.
AC TRACTION UNIT RAILFAN NOTES
A NAFTA TRADE (OF SORTS) - On March 24th, SD90/43AC locomotives 8026, 8072 and 8075 were part of a six unit consist powering train XHKNP-24; this is an extra train which operated from Hinkle, Oregon toward Eastport, Idaho, where there is an interchange point with the Canadian Pacific railroad (Regular run-thru operations between these locations and companies has been a longtime partnership). The CPRS received this trio so as to conduct performance testing, as they were contemplating a purchase order for GM AC Traction locomotives (It turned out to be a successful venture, as they did order some 5000 horsepower SD80MAC's).
As horsepower compensation, UP was loaned three CP Rail C44AC locomotives; the unit numbers are the 9515, 9529, and 9551. They came onto the UP on March 25th via the UP-BNSF interchange at Spokane, Washington. The CP Rail units have remained together and have been working in the Hinkle to Eastport corridor on the UP-CPRS run-thru jobs in conventional service format (The CP units are non-upgrade able versions to 6000 horsepower. They are outfitted with the stand alone DP control boxes, IFC and WABCO E3102 brake systems).
AN INTERESTING CONSIST - As North Platte, Nebraska is one of the busiest places for seeing various types of motive power consists, I was looking at an LZ lineup for them in TCS and found yet another circumstance in motive power consists I didn't think would happen, at least not this soon: On April 11th, there was an empty unit coal train, the CSYMB-11, which came into Bailey Yard with 107 cars powered by a trio of GM AC Traction units. SD90/43AC unit No. 8112 was leading a pair of BN SD70MAC's; their unit numbers were the 9424 and the 9582.
I cannot for certain tell you whether or not this is the first time such a lashup of these models has occurred on the UP, but nonetheless, it is an event which got my attention (for me personally, I would like someday to step aboard one of the four pre-production SD60MAC units. As we know, these guys were the big trailblazers for what is now known as the AC revolution. Unit No. 9502 has been in Ft. Worth in the last month as the middle unit of the HL&P unit coal trains).
NAME THAT CONDITION First, it was the "boogie shake". Now comes the latest name for the shuddering effect sometimes produced by the AC Traction models of locomotives. This co-worker calls it "The AC Shuffle".
Who knows what other colorful terms for this are out there? If you do have one, leave it at my E-Mail address, or by phone at (817) 878-4528.