Traction Motors: What could go wrong?

[zippy71264]

Hi everyone,

What is the worst thing you know of that can happen if a traction motor was to fail?

Thanks

Zippy

 

[coppercapped]

Hmm! 'Were to fail?' In what way? Electrically, mechanically, magnetically, thermally? Do you mean all types of traction motor or do you have a specific type of motor in mind?

 

[millemille]

A mate of mine was working in Connex South Eastern's Control in the early days of the Networkers.

He's on a night shift when a driver bells him up from just outside Gravesend, country side on the up line.

My mate heard the driver say "My tractions dropped out, what do you want me to do?".

"Isolate it.." says my mate "...and proceed to Gravesend and the Line of Route fitter will meet you there".

"You sure?" asks the driver.

"Yes driver" says my mate.

Driver duly does as instructed. Taking out 1/4 of mile of sleepers with the traction motor that had dropped off the bogie and was hanging by the power cables as it banged and bounced along the 4 foot.....

 

[Tynwald]

What a question, and were would you start to answer it. Perhaps some studying into how motors work, and their control systems, and mechanical interfaces. see you in a couple of years !! Well thats how long at least it took me in my apprenticeship, and that was only a start.

 

[zippy71264]

Hmm! 'Were to fail?' In what way? Electrically, mechanically, magnetically, thermally? Do you mean all types of traction motor or do you have a specific type of motor in mind?

Thanks for the reply.

This is more a general question. Trying to wrap my head around the possible failure modes of traction motors and the damage they could do to the train if they were to fail. e.g. could it set on fire, yes, would it set the whole carriage on fire? Not sure.

In the event of failure under any event, would the driver manually isolate? Or is there an automatic system that does that?

 

[zippy71264]

A mate of mine was working in Connex South Eastern's Control in the early days of the Networkers.

He's on a night shift when a driver bells him up from just outside Gravesend, country side on the up line.

My mate heard the driver say "My tractions dropped out, what do you want me to do?".

"Isolate it.." says my mate "...and proceed to Gravesend and the Line of Route fitter will meet you there".

"You sure?" asks the driver.

"Yes driver" says my mate.

Driver duly does as instructed. Taking out 1/4 of mile of sleepers with the traction motor that had dropped off the bogie and was hanging by the power cables as it banged and bounced along the 4 foot.....

this is good.

 

[zippy71264]

What a question, and were would you start to answer it. Perhaps some studying into how motors work, and their control systems, and mechanical interfaces. see you in a couple of years !! Well thats how long at least it took me in my apprenticeship, and that was only a start.

Thanks. The motors side isn't an issue, it's the subsequent damage to the train that I'm unsure of if a failure was to occur.

 

[edwin_m]

I can't think of any instance where a traction motor has started a fire. I presume in the event of an internal short circuit something would trip out (or burn out!) before that happened. Transformers have caught fire or exploded in the past but I don't believe the causes were related to traction motors.

There have been occasions where parts have dropped off a traction motor and caused damage to the train behind, one of the most serious being at Darlington in the 1970s when it disabled most of the brakes and caused a collision. It should be searchable on railwaysarchive.co.uk, but I can't link or quote as the site seems to be down at the moment.

 

[pdeaves]

I suspect a fairly serious failure mode would be a bearing seizing and everything locking up.

 

[Spartacus]

I'm sure I've heard of the motors on a Peak being hooked up wrong after an exam and the wheels moved in different directions, this only realised after the loco had made it's way from Toton as far as Clay Cross!

 

[Ken H]

With DC motors i think the big one is a flashover. This is when the electricity arcs destroying the motor on the way.

The other one is when the motor overspeeds and the armature bursts due to centrifugal force.

I dont want to be on a train when either of these happen!

(In physics there is no centrifugal force. There is Newton saying the object wants to go in a straight line and a centripetal force stops it.)

 

[Taunton]

Probably when the supporting bolts fail and the whole motor falls out, causing a derailment. The Central Line had this happen in 2003, not for the only time, with multiple passenger injuries https://www.theguardian.com/uk/2003/jun/02/london.transport

 

[Dstock7080]

The other one is when the motor overspeeds and the armature bursts due to centrifugal force.

1981/82 had taken a brand new LU D Stock out of depot, after ripping protective plastic from drivers seats, having only got passed the first station when the armature on one motor blew, lots of white smoke, motor locked!

 

[matchmaker]

I suspect a fairly serious failure mode would be a bearing seizing and everything locking up.

Did this not cause an HST derailment on the ECML? Northallerton, November 1979.

 

[Dunfanaghy Rd]

On at least 1 occasion a 59 has had a seized traction motor. The remedy was to get into the gearcase and burn off the end of the drive shaft (and pinion) to make the free axle to rotate. Add in multiple dealy minutes and it becomes a very expensive failure.
Pat

 

[Richard Scott]

I would imagine a fire is quite an issue - certainly a few locos withdrawn due to that. Someone showed me a picture of a 45 (think it was 45124) with a traction motor fire at Leicester - finished it off. 45149 caused an issue due to bearing failure on Dunstable branch (think gear pinion got gas axed off so they could move it, can anyone quantify that?), it got dumped at Cricklewood but it was that failure that ensured its survival.
I think flashovers could actually just be a minor issue, seem to remember they were so common on Deltics drivers were told to shut off power, wait and then reapply, if no bangs all was good. However flashovers can also wreck a motor, often taking the generator out in the process.

 

[Ashley Hill]

 

[Richard Scott]

That was due to a brush box not being attached correctly and shorted on the motor casing, wasn't a flashover, if I remember correctly.

 

[Ashley Hill]

Thanks for the correction,I was going by the info on another you tube post of the same incident.

 

[36270k]

What appeared to be a traction motor fire was often oily dirt burning from brake block sparks. Class 47's were often prone to this due to numerous oil leaks. BR maintenance standards were extremely poor in the 1960/1970's

Class 40's in their early days were prone to traction motor flashovers. They were all fitted with an updated type of motor.

 

[DarloRich]

surely the dreaded traction motor flash over is a bad thing. No I have no idea what that means either................

 

[Richard Scott]

surely the dreaded traction motor flash over is a bad thing. No I have no idea what that means either................

A flashover occurs when the positive and negative sides of the motor short together due to an arc across the insulation hence term flashover.
Certain locos were more prone to generator flashovers due to higher voltages used in series-parallel arrangements such as found in 50s (in a generator that was already nigh on its working limit). 47s initially were series-parallel but a change made to all parallel in later builds to reduce this issue. Locos like 45s were all parallel from the start making them more reliable in this area.

 

[CW2]

I once had 47851 and 47847 in tandem on the 1418 Padd - Birmingham. 847 was defective and being moved for repairs, but the driver was seemingly unaware, and opened it up fully leaving Paddington. Around Westbourne Park there was a loud bang and a sheet of flame shot out from the front bogie, several metres long. We ground to a halt, and both drivers looked out, a bit mystified, then thrashed away happily to Slough. During the station stop there I advised the driver what I had seen, so he decided to join his mate in the front cab and leave 847 idling. Subsequently it was several weeks awaiting / on repair for a traction motor change.

 

[DarloRich]

A flashover occurs when the positive and negative sides of the motor short together due to an arc across the insulation hence term flashover.
Certain locos were more prone to generator flashovers due to higher voltages used in series-parallel arrangements such as found in 50s (in a generator that was already nigh on its working limit). 47s initially were series-parallel but a change made to all parallel in later builds to reduce this issue. Locos like 45s were all parallel from the start making them more reliable in this area.

Thanks - I was thinking of the 50's. Flashovers seemed to do for them on a regular basis.

 

[Ken H]

Thanks - I was thinking of the 50's. Flashovers seemed to do for them on a regular basis.

there was a fred about this. Google found it for me!

what exactly is "flashover" damage please?

recently picked up a old video (yes that old!!!) on the class 50s and the the narrator kept commenting on the problems they had with flashover damage on the LSW route. However, it never explains what flashover damage actually was/is! Can someone please enlighten me?

www.railforums.co.uk

 

[Shimbleshanks]

I've heard the expression: 'Throwing the plates off the traction motors'. No idea what it means, though...