Rheostatic Braking

[darwins]

Which diesel electric locomotives and multiple units in service at present have rheostatic braking?

Can anyone recommend any online or easily accessible source of information that gives the rheostatic braking force vs speed curves for any of these?

[The only UK loco I have so far seen one of these curves published for is the class 85 electric:



...come to think of it I would quite like to see what the curves look like for more modern electric traction too.]

 

[hexagon789]

Which diesel electric locomotives and multiple units in service at present have rheostatic braking?

Can anyone recommend any online or easily accessible source of information that gives the rheostatic braking force vs speed curves for any of these?

[The only UK loco I have so far seen one of these curves published for is the class 85 electric:

View attachment 106985

...come to think of it I would quite like to see what the curves look like for more modern electric traction too.]

I've seen ones for 86s and 87s but I cannot for the life of me recall where.

As for those equipped with rheostatic braking - DE locos you have 68s and 70s (the latter of which also have a regen function I believe), for MUs do you mean of any type, ie not purely Diesel-electric?

 

[DanNCL]

91s have rheostatic braking, I too would be interested in seeing the rheostatic brake curves for the electric locos.

 

[jfollows]

Class 92 because its failure was mentioned in the runaway potential accident report in Edinburgh

 

[ac6000cw]

DE locos you have 68s and 70s (the latter of which also have a regen function I believe)

AFAIK only in the sense of being able to power the auxiliary loads (fans etc.) from the traction motor power - they don't have any energy storage.

It would be interesting to know if the Cl.70s have similar rheostatic braking capability as the GE/Wabtec US locos, which can dissipate as much (or more) power in rheostatic/dynamic braking as in traction. That also means they can do 'self load' engine testing by dumping all the engine power into the brake resistance grids ('Run 8' while stationary...).

 

[hwl]

The re

It would be interesting to know if the Cl.70s have similar rheostatic braking capability as the GE/Wabtec US locos, which can dissipate as much (or more) power in rheostatic/dynamic braking as in traction. That also means they can do 'self load' engine testing by dumping all the engine power into the brake resistance grids ('Run 8' while stationary...).

The resistors aren't big enough for full power by a long way...

 

[hexagon789]

AFAIK only in the sense of being able to power the auxiliary loads (fans etc.) from the traction motor power - they don't have any energy storage.

Yes, I should've been more specific about that. I'm not sure how else you would describe though it other than 'regenerative' as it does recover braking energy.

 

[darwins]

I've seen ones for 86s and 87s but I cannot for the life of me recall where.

As for those equipped with rheostatic braking - DE locos you have 68s and 70s (the latter of which also have a regen function I believe), for MUs do you mean of any type, ie not purely Diesel-electric?

For MUs, I wanted to know if there was any equipment on DEMU - 220/221 etc. and also any information about the capabilities of the 80x units, particularly when on diesel power.

I know there are some units with hydro-mechanical transmissions that include retarders - 175, 180, 185 I believe. It would be interesting to see published curves for these too, and in fact the general performance curves of the Voith transmissions.

The resistors aren't big enough for full power by a long way...

Any idea how big the resistors are and how much power they can dissipate before overheating? It might be possible to estimate the braking forces from that.

Historically class 50 would also be of interest.

 

[hexagon789]

For MUs, I wanted to know if there was any equipment on DEMU - 220/221 etc. and also any information about the capabilities of the 80x units, particularly when on diesel power.

22x all have rheostatic braking.

I forget the precise situation with 80x, certainly 801 & 803 do regen; 800s are I believe regen only while 802s do rheo or regen as required.

I know there are some units with hydro-mechanical transmissions that include retarders - 175, 180, 185 I believe. It would be interesting to see published curves for these too, and in fact the general performance curves of the Voith transmissions.

They are disabled on 175s and 180s.

Historically class 50 would also be of interest.

Need to look it out, but I think I have a book which mentions the rheo on 50s.

 

[D821]

507s & 508s have them, and disc breaking, I believe.

 

[hexagon789]

507s & 508s have them, and disc breaking, I believe.

Yes and 313s

 

[ac6000cw]

The re

The resistors aren't big enough for full power by a long way...

Thanks - that's what I suspected (given the space constraints of a UK sized loco).

Historically class 50 would also be of interest.

Based on the limited information in the Class 50 'Haynes Manual' book, maximum rheostatic braking current is about 1650A at 28mph, reducing at lower speeds. For comparison, traction current limit (in weak-field) is 2400A.

 

[DaveTM]

313s on Southern still have some (or maybe all) of the equipment required to do rheostatic braking. My understanding is that the heat generated in the resistors was once used to heat the saloon. However as drivers we are required to keep the circuit breaker on the cab back wall off, and rumours persist that (a) the circuit breaker is disconnected anyway, and (b) we don't use it because the trains had a habit of catching fire.

On 377s we have "blended braking"; meaning that putting the controller in step 1 brake results in a fixed decelleration rate whether the kinetic energy is being turned into brake dust, power returned to the 3rd rail, or hot resistor grids. I suspect that the resistor grids on the train can accept at least as much power as the 3rd rail because I do not notice any (even momentary) change in decelleration when the train goes over a known 3rd rail gap, even when there is a train absorbing my energy on an adjacent track or visibly in the section in front of me.

 

[Efini92]

Class 92 because its failure was mentioned in the runaway potential accident report in Edinburgh

Isn’t the class 92 regenerative?

 

[D365]

Isn’t the class 92 regenerative?

Anything that regenerates must have the capability to fall back to rheostatic.

 

[Shwam3]

Anything that regenerates must have the capability to fall back to rheostatic.

Not the case. 745s only have regen braking, falling back to friction braking through neutral sections. There may be other traction with a similar setup.

 

[king_walnut]

313s on Southern still have some (or maybe all) of the equipment required to do rheostatic braking. My understanding is that the heat generated in the resistors was once used to heat the saloon. However as drivers we are required to keep the circuit breaker on the cab back wall off, and rumours persist that (a) the circuit breaker is disconnected anyway, and (b) we don't use it because the trains had a habit of catching fire.

On 377s we have "blended braking"; meaning that putting the controller in step 1 brake results in a fixed decelleration rate whether the kinetic energy is being turned into brake dust, power returned to the 3rd rail, or hot resistor grids. I suspect that the resistor grids on the train can accept at least as much power as the 3rd rail because I do not notice any (even momentary) change in decelleration when the train goes over a known 3rd rail gap, even when there is a train absorbing my energy on an adjacent track or visibly in the section in front of me.

Ah that's why the Dynamic Brake Control MCB is always down? Always wondered why but didn't care enough to ask haha

 

[aleggatta]

313s on Southern still have some (or maybe all) of the equipment required to do rheostatic braking. My understanding is that the heat generated in the resistors was once used to heat the saloon. However as drivers we are required to keep the circuit breaker on the cab back wall off, and rumours persist that (a) the circuit breaker is disconnected anyway, and (b) we don't use it because the trains had a habit of catching fire.

correct. The rheo brake was isolated when they were up in London and they have never been reinstated, not wanting to risk an old system that carries high current that has been out of use for some time. The resistor grids (traction and braking) on all the 313s were swapped out a few years ago to get rid of some hazardous materials, and I always thought it would have been a prime opportunity to try and reinstate the system, but by all accounts it isn’t a very ‘clean’ rheo brake and as such wasn’t deemed necessary to reinstate (much to the frustration of those of us replacing brake pads!)

 

[Efini92]

Anything that regenerates must have the capability to fall back to rheostatic.

The class 331’s don’t have that capability. They revert back to friction only.

 

[jfollows]

Isn’t the class 92 regenerative?

Both

 

[Taunton]

It would be interesting to know if the Cl.70s have similar rheostatic braking capability as the GE/Wabtec US locos, which can dissipate as much (or more) power in rheostatic/dynamic braking as in traction. That also means they can do 'self load' engine testing by dumping all the engine power into the brake resistance grids ('Run 8' while stationary...).

The US manufacturers ("Dynamic braking" over there) offer a range of capacities, up through Extended Range Dynamic Braking, which I guess is being referred to here, with huge brake resistor elements along the roofline. Only those railroads with substantial downhills and main line freights order these, often with four or so such locomotives all braking like this.

 

[darwins]

Anything that regenerates must have the capability to fall back to rheostatic.

A good idea, but not always followed in practice. Thinking to older dc electrics now. Classes 76 and 77 were both built with regenerative braking. The current generated in the motors could be fed back directly or via the traction resistors with motors connected in either parallel or series (or series-parallel for the 77) to the power line. The traction resistors could be used to control the current, but not to dump all the power. Finding more braking was needed at lower speeds the class 76 later had a separate rheostatic braking system added for slow speeds. In this arrangement all the power generated was dumped through a grid of huge resistors.

Similarly with the first regenerative braked stock in UK, the metadyne fitted London Transport O stock. This could feed back to the third rail, but not have an arrangement to dump the power through resistors if this failed.

 

[hexagon789]

Similarly with the first regenerative braked stock in UK, the metadyne fitted London Transport O stock. This could feed back to the third rail, but not have an arrangement to dump the power through resistors if this failed.

I thought that on the contrary 'O stock' not only had braking resistors but due to the fact the substations and power system were not really designed to accept regeneration that more often than not the 'O stock' reverted to rheostatic braking instead of using the regen.

 

[darwins]

I thought that on the contrary 'O stock' not only had braking resistors but due to the fact the substations and power system were not really designed to accept regeneration that more often than not the 'O stock' reverted to rheostatic braking instead of using the regen.

You could be right. I know there were problems with the feeding back - hence many more years till it was tried again. Anyone have a copy of Agnew to hand?

 

[Ken H]

A good idea, but not always followed in practice. Thinking to older dc electrics now. Classes 76 and 77 were both built with regenerative braking. The current generated in the motors could be fed back directly or via the traction resistors with motors connected in either parallel or series (or series-parallel for the 77) to the power line. The traction resistors could be used to control the current, but not to dump all the power. Finding more braking was needed at lower speeds the class 76 later had a separate rheostatic braking system added for slow speeds. In this arrangement all the power generated was dumped through a grid of huge resistors.

Similarly with the first regenerative braked stock in UK, the metadyne fitted London Transport O stock. This could feed back to the third rail, but not have an arrangement to dump the power through resistors if this failed.

I thought the 76's were retrofitted with rheostatic braking because of a reduction of woodhead traffic, meaning there was less likely to have a train to accept the regen current. Or have I got that wrong?

 

[darwins]

I thought the 76's were retrofitted with rheostatic braking because of a reduction of woodhead traffic, meaning there was less likely to have a train to accept the regen current. Or have I got that wrong?

It was installed at quite an early date, I believe to help at low speeds.

The driver's manual states the following:

For (class 76) Bo-Bo: regenerative braking with motors in series can be used for speeds between 16 mph and 33 mph or with motors in parallel between 30 mph and 55 mph. "The locomotive can not be stopped by this brake and the power of the rheostatic brake should be used below 16 mph."

It goes on to say that the rheostatic brake can be used for speeds below 20 mph.

 

[ac6000cw]

I thought the 76's were retrofitted with rheostatic braking because of a reduction of woodhead traffic, meaning there was less likely to have a train to accept the regen current. Or have I got that wrong?

From memory, at least some of the feeder stations on the Woodhead electrification had resistor banks which were switched in to absorb the regen braking energy if necessary i.e. when there were no other trains around to use it. I think there were maintenance issues with that equipment later on, so it may have been taken out of use. That may also have been a factor in adding rheostatic braking capability to the locos.

 

[DownFast]

I forget the precise situation with 80x, certainly 801 & 803 do regen; 800s are I believe regen only while 802s do rheo or regen as required.

800s do have rheostatic braking but the resistors are only small and designed for short bursts (5 seconds or so is what I've heard) when regen cannot be used, such as when the VCB is open while passing through a neutral section. 802s have full size resistors so can use regen in electric and rheo in diesel, but 800s are friction only in diesel because of the smaller resistors. 800+802 in multiple will also be friction only in diesel.

 

[hexagon789]

800s do have rheostatic braking but the resistors are only small and designed for short bursts (5 seconds or so is what I've heard) when regen cannot be used, such as when the VCB is open while passing through a neutral section. 802s have full size resistors so can use regen in electric and rheo in diesel, but 800s are friction only in diesel because of the smaller resistors. 800+802 in multiple will also be friction only in diesel.

That was it, I couldn't recall the precise details but your post has jogged the old brainbox

 

[D365]

800s do have rheostatic braking but the resistors are only small and designed for short bursts (5 seconds or so is what I've heard) when regen cannot be used, such as when the VCB is open while passing through a neutral section. 802s have full size resistors so can use regen in electric and rheo in diesel, but 800s are friction only in diesel because of the smaller resistors. 800+802 in multiple will also be friction only in diesel.

So there is a technical reason for the 802s to be distinct from the 800s. That’ll appease the TOPS fanatics!