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 Post subject: Traction Motors
PostPosted: Wed Sep 16, 2020 9:44 pm 

Joined: Sun Jul 20, 2008 12:21 am
Posts: 58
Today I was asked a question which got me to thinking:

Someone asked me what I think about running electric railroad
cars such as old South Shore cars during the winter months in Wisconsin.

The reason for the question is because this person has been told
that operating interurbans and streetcars at a museum setting in winter
can be very harsh on motors. The supposed reason for this harshness
is because the motors never get fully warmed up while running at
a typical museum.

Thus, (the theory goes), there will be condensation buildup on coils
and commutator as the car runs. Commutator brushes will rub off
a mixture of moisture and brush dust, forming a sort of mud that
tends to cake things up and short things out.

That, plus the moisture on the windings themselves is present.

So, it has been said that this can lead to motor failure.

My questions to the group here are:

1) How severe is this?
2) What, if any, forms of prevention and/or mitigation can be had?

I would think that maybe some way to ventilate, and dry out these
motors after a Christmas train, might help this situation.

Any and all discussion is welcome! Any ideas out there?

Thank You.

Chuck


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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 2:43 am 

Joined: Mon Jul 02, 2018 8:04 pm
Posts: 241
I have never heard that theory. Considering there is considerably more condensation in the hot, humid, Summer months of the coastal states. I would expect to see more problems as the humidity rises especially after a good rain. I have also never heard of electric motors needing to "warm up" before operation. Sure there is plenty of old electric motors that you need to wait a minute or two before it gets to full RPM. But as far as heating up a motor with a propane burner or something never seen it or heard of it. Also if you have enough carbon build up in a traction motor that it is gumming things up, you are not doing very good periodic maintenance on that motor.


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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 2:49 am 

Joined: Thu May 24, 2012 1:37 pm
Posts: 1386
When I was looking at the Electroliner/Liberty Liner at Rockhill for a proposed Memphis transit service, a member of the staff there brought up a very similar issue, involving not a traction motor per se but a motor-generator. If this was started in cooler weather, condensation on the commutator could lead to fairly dramatic and expensive flashover; to get rid of the problem, the unit was installed in a fairly well-sealed box which contained an incandescent bulb, which was left on overnight to preclude any condensation from forming. I was told this was cheap insurance against a very expensive trouble.

It does stand to reason there might be a comparable issue for other electric components subjected to sudden heavy loading while still 'wet with condensation' (or frosty). The "answer" there might be to restrict loading until the devices had heated up enough to be dry. something perhaps not as easily done as thought about if no fine resistance control were provided and the motors did not have cooling fans or blowers to help any moisture evaporate.

You would certainly not solve this with any sort of torch or contact heating a la diesel block heaters, although as noted some form of resistance heating close to the affected areas might be valuable. I might be tempted to arrange for some kind of blower arranged to deliver hot and perhaps desiccated air to the area of motors or other devices for some effective length of time before putting them under traction power or starting them in service.

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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 3:29 am 

Joined: Mon Jul 02, 2018 8:04 pm
Posts: 241
When I was working for the railroad in Alaska, I asked a question to a locomotive electrician on a very cold day. The question was "this cold weather must be hard on the locomotive electrical system". He said "no electricity flows better in cold weather". He was right. Electricity flows better the colder it gets. After cooled to -273° Celsius there is no electrical resistance which is why super computers need such massive cooling systems.

I also know that the #1 killer of electrical motors is heat. So I would expect less problems in the Winter time and more in the Summer. As far as the condensation issue. I can't ever recall in all the manuals I own, ever reading about condensation. If there is arcing or flash over due to condensation then you already have some serious problems with that motor. When I was in my 20's I was a mechanic at a water park. We had some huge 500hp motors that ran blowers for the wave pool. The ceiling in that room were dripping water constantly and it was extremely humid. Every morning I would start those up with out any problems.

You would also be surprised what a poor conductor electricity is in pure water. This guy sticks two wires in a glass of water and moves his finger around in it https://www.youtube.com/watch?v=dcrY59nGxBg


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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 4:04 am 

Joined: Thu May 24, 2012 1:37 pm
Posts: 1386
Quote:
"You would also be surprised what a poor conductor electricity is in pure water."
I think a large part of the actual issue is that the condensation does not remain 'pure' -- it absorbs contaminants from polluted air and from any dust or dirt, possibly including copper and carbon particles, around the commutator area. I don't think it takes much conductive 'loading' to make water a reasonable ionic conductor -- the relationship between this and sustaining the high-voltage high-current 'sheet arc' that is the initial sign of a flashover is less certain. I do not have firsthand experience, but I suspect there are people at Rockhill who can flesh out the actual story with some precision as to details, or will know how to obtain them.

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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 10:24 am 

Joined: Tue Dec 18, 2007 10:28 am
Posts: 33
Location: Central Pennsylvania
I’ve been a volunteer at Rockhill Trolley Museum in one capacity or another for the past 21 years. During that time I’ve led the effort to return both of their PCC cars to operable condition and was part of the team that returned Liberty Liner Independence Hall to limited operating condition back in 2014. I also still perform the annual inspection and maintenance on the museum’s two PCC cars.

I’ve never had any problems with motor generators operating in colder weather. For example, at the 2014 Winterfest (annual gathering of east coast trolley museums), both of the museum’s PCC cars and the Independence Hall successfully operated on a cold and snowy day. Several other museums run their PCC cars in winter as well with no special precautions or extra efforts.

PSCT PCC #6 sat in dead storage for 10 years before it was operated again and it still runs fine with the MG it came with 9 years later (other than some noise caused by one fan blade in one of the blowers which is broken at one end and thus rattles). PTC #2743 sat for 5 years between the time it was taken out of service at the museum and its return to operation, again, with no MG problems in the 11 years since.

In each case, prior to starting the MG for the first time after years of sitting idle, the unit was carefully blown clean, visually inspected, commutators cleaned, brush holders cleaned, brushes cleaned and inspected, and bearings lubricated before power was applied. MGs in a PCC run at a constant speed except for fluctuations in line voltage and load, but there is no ramp up/down.

I’m not sure who the Liberty Liner MG was discussed with, but the issues with the MG itself are likely due to its age and marginal condition. Only one of the train’s MGs has been operable for some time, and the functional unit has not been overhauled in many decades. The train sat inoperable for many years in Upper Darby prior to going to the museum nearly 40 years ago, and ran on and off at the museum for about a decade before going out of service at the museum for another decade prior to its return to operation for a few trips per year in 2014.

Bottom line, in my opinion the fundamentals of good preventive maintenance on vintage traction motors (periodic cleanings, inspections, appropriate lubrication) is the best defense against failures.

Thanks,
Matt Nawn


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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 1:15 pm 
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Joined: Fri Oct 24, 2008 9:05 pm
Posts: 882
Location: MA
Unlike some memes that water is not a good conductor condensation can and has caused problems there this very serious accident involving electrician who had his multimeter out in hot and humid weather and then took it inside and probe some high voltage lines.


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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 2:18 pm 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2589
Location: Northern Illinois
Tom F wrote:
When I was in my 20's I was a mechanic at a water park. We had some huge 500hp motors that ran blowers for the wave pool. The ceiling in that room were dripping water constantly and it was extremely humid. Every morning I would start those up with out any problems.


Those were undoubtedly induction motors. There is really no reason that an induction motor with modern insulation shouldn't run even if filled with water, other than the turbulence will likely tear the windings up.

DC traction motors are a different beast. However the first sixty years of diesel locomotives used DC motors exclusively, and those motors aren't going to be pre-warmed if the unit has been sitting in the yard pumping air for a couple hours on a winter night before starting a maximum tonnage train. I would think that if condensation in the motors had proven to be a significant problem, it would have been addressed by now.

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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 4:46 pm 
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Joined: Tue Feb 20, 2018 7:08 pm
Posts: 163
Location: Alberta, Canada
Dennis Storzek wrote:
DC traction motors are a different beast. However the first sixty years of diesel locomotives used DC motors exclusively, and those motors aren't going to be pre-warmed if the unit has been sitting in the yard pumping air for a couple hours on a winter night before starting a maximum tonnage train. I would think that if condensation in the motors had proven to be a significant problem, it would have been addressed by now.


Wouldn't the airflow from the traction motor blowers take care of any condensation, as well as preventing it from building up?

Most if not all railroad and diesel-electric operating manuals contain strict instructions to never run through water that is more than a few inches above the railhead. If you cannot stop before the water our instructions also say to move the throttle to idle, centre the reverser and then open the throttle again to a high position, in an attempt to pressurize the motors with air and keep as much water out of them as possible.

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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 8:23 pm 

Joined: Sun Aug 22, 2004 9:54 am
Posts: 928
Location: NJ
Traction motor blowers will help keep moisture out of motors, IF the unit has those blowers. The EMD SW-1 did not have TM blowers, nor did many (most?) of the GE 'industrial' or smaller railroad engines, such as the 44 tonner. I don't think too many trolley cars or interurbans had TM blowers, either.


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 Post subject: Re: Traction Motors
PostPosted: Thu Sep 17, 2020 9:24 pm 

Joined: Sun Jun 23, 2013 1:16 pm
Posts: 121
Most older locomotives would be equipped with "Ground Relay" protection.

Snow (moisture) getting inside the traction motors would cause it to trip out.

Were these types of "cars" ever set up to have GR protection?


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 Post subject: Re: Traction Motors
PostPosted: Fri Sep 18, 2020 10:26 am 

Joined: Mon Aug 23, 2004 3:01 pm
Posts: 1565
Location: SouthEast Pennsylvania
What happened to these South Shore motors when their cars were moved around the shops near Michigan City, Ind.?


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 Post subject: Re: Traction Motors
PostPosted: Fri Sep 18, 2020 5:12 pm 

Joined: Fri Mar 26, 2010 11:43 am
Posts: 634
generally, all it takes to prevent condensation, is for the item to be slightly warmer them ambient temp. If you had the car sitting outside, and brought it into a warm shop, you might get condensation. If it was cold, and the motors were warming up slower then the ambient temp, it might get condensation. If the motors are warming up even slightly faster then ambient temp, you should be fine.

They make heaters for strapping to motor cans. You could easily get heaters to plug into 120 or 240, or even wire some in series to operate off of 600 volts DC, etc.


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 Post subject: Re: Traction Motors
PostPosted: Fri Sep 18, 2020 8:17 pm 

Joined: Fri Dec 22, 2017 6:47 pm
Posts: 565
Location: Philadelphia, PA
I don't know about condensation but snow can wreak havoc with traction motors.

The Reading Company had no end of trouble with snow getting into Old/Blue MU car motors and causing failures. And ridership went up in the snow as people took the train instead of driving to work.

A solution came after the spare motors were used up and cars could not run until more motors were repaired. RDG took 8 dead MU cars, left a pan up for light and heat (the cars were connected on the 11,000 VAC side) and pulled them with a pair of diesels, first GP35's, then new GP39-2's on the West Trenton Line. That was out of Reading Terminal, not the current underground stations.

Phil Mulligan


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 Post subject: Re: Traction Motors
PostPosted: Fri Sep 18, 2020 10:21 pm 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2589
Location: Northern Illinois
Pegasuspinto wrote:
generally, all it takes to prevent condensation, is for the item to be slightly warmer them ambient temp.


Which means that with a car parked outside, as soon as you take the first point on the controller, the motors are warmer than the ambient temperature. Not much, but warmer, and the more you run, the warmer they get. There is no way that they will become colder than ambient, unless, as you say, the car is brought into a warm shop.

Years ago when I worked for the Chicago Transit Authority, I know they fitted linen covers over the ventilating openings on the motors during the winter. I seem to recall much more motor trouble on lines that ran in the expressway medians, which I think was attributed to the amount of salt in that environment.

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