Rheostatic/dynamic EMU braking.

[notadriver]

Can anyone tell me if the dynamic braking on DC motored units such as class 313/315/317 and 319 works?

Many thanks.

 

[samuelmorris]

I can't say I've heard it working, and I would expect to if it was operational. I didn't even think most of those classes had it fitted. Can't provide anything scientific on that though!

 

[AM9]

I've often though about that when on a 319 approaching St Albans. Considering that they are decelerating from 90 - 100 when on the fast lines, the braking seems smooth as would be the case for rheo. or regen., and it definitely changes to something more 'mechanical' at about 15mph when slowing to a halt. The mechanical feel seems to vary between individual units, which is probably indicative of different disc/pad condition.

 

[edwin_m]

Do you get motor hum when sitting in the motor coach when the train is slowing down?

 

[notadriver]

The sound of the motors if being used to slow down would be quite loud and obvious wouldn't it ? I'm assuming a reverse pitch to acceleration?

 

[AM9]

Do you get motor hum when sitting in the motor coach when the train is slowing down?

I think that there is a motor whine, i.e. some brush noise and the final drive gearteeth under torque. If it is regen., I would expect there to be some 50Hz hum from the transformer as it steps the locally inverted ac back up to enable injection into the OHLE. If the system is rheo. only, then the DC motor whine is probably most of the sound.
I can't remember the exact sounds, but it felt like motor braking rather than friction.

 

[Silverlinky]

It was fitted and it worked on Silverlinks 313's....but it was isolated and we weren't allowed to use it!

 

[samuelmorris]

I think that there is a motor whine, i.e. some brush noise and the final drive gearteeth under torque. If it is regen., I would expect there to be some 50Hz hum from the transformer as it steps the locally inverted ac back up to enable injection into the OHLE. If the system is rheo. only, then the DC motor whine is probably most of the sound.
I can't remember the exact sounds, but it felt like motor braking rather than friction.

With DC motor stuff remember it's important to distinguish traction motor noise from the rail noise, which can be quite similar at times - much easier to distinguish on AC motor stock (which is far more likely to have rheostatic or regen braking).

 

[O L Leigh]

Can anyone tell me if the dynamic braking on DC motored units such as class 313/315/317 and 319 works?

Many thanks.

Cl315 and Cl317 certainly don't have dynamic brakes, and I'm fairly certain that Cl319s don't either. So the answer is no, they don't work.

O L Leigh

 

[notadriver]

Thanks O L Leigh. I just checked. Class 313/315 have them but it must have been disabled but was surprised that classes 317/319 etc don't. I suppose it's because the tube stock uses it all the time.

 

[W230]

I've often though about that when on a 319 approaching St Albans. Considering that they are decelerating from 90 - 100 when on the fast lines, the braking seems smooth as would be the case for rheo. or regen., and it definitely changes to something more 'mechanical' at about 15mph when slowing to a halt. The mechanical feel seems to vary between individual units, which is probably indicative of different disc/pad condition.

No regen on 319s. I would suggest that it starts to feel harsher around 15mph as changing between step 1 and step 2 brake force will bite a lot more at that speed than at 90mph.

 

[SPADTrap]

First thing most do when opening up a 313 is check to make sure the dynamics are isolated

Demonstrator 317 722 has dynamics and it does work however this is the only one, it has AC motors.

 

[bramling]

First thing most do when opening up a 313 is check to make sure the dynamics are isolated

Demonstrator 317 722 has dynamics and it does work however this is the only one, it has AC motors.

I don't tend to use the GN 313s too much, however I've definitely heard it used on many if not most journeys.

I'm sure I recall that it was never pursued on the classes 317-322 because with only one motor car it was felt that the benefits did not justify the extra cost and complexity.

 

[edwin_m]

I believe regenerative braking under AC only came in with three-phase drives and AC motors. Older technology can't generate AC at exactly the same frequency and phase as the supply, which is necessary to regenerate successfully. Some might have had rheostatic braking.

 

[SPADTrap]

I don't tend to use the GN 313s too much, however I've definitely heard it used on many if not most journeys.

I'm sure I recall that it was never pursued on the classes 317-322 because with only one motor car it was felt that the benefits did not justify the extra cost and complexity.

It was a bit of a problem child getting it working on 722!

 

[notadriver]

I believe regenerative braking under AC only came in with three-phase drives and AC motors. Older technology can't generate AC at exactly the same frequency and phase as the supply, which is necessary to regenerate successfully. Some might have had rheostatic braking.

Yes what's interesting is that only 313/314/315 had rheo/dynamic fitted and it seems to be isolated. Later DC motored units such as 317-322 don't have it - maybe because as suggested it wasn't worth the complexity and possibly one motor cpatch? Thinking about it 313-315s have two motor coaches and of course the tube 1967 stock - C stock all had it but they all had at least 2 motorised vehicles.

 

[Taunton]

I believe regenerative braking under AC only came in with three-phase drives and AC motors. Older technology can't generate AC at exactly the same frequency and phase as the supply, which is necessary to regenerate successfully. Some might have had rheostatic braking.

I believe the Swiss, pretty much all ac and all regen equipped, cracked this long ago.

 

[HSTEd]

With a lower frequency electricity supply, such as prevails in Switzerland and Germany, many locomotives ran on AC without a rectifier using Universal motors which I believe can regenerate assuming there is an AC voltage present on the line to allow the motor coils to excite. This is not considered practical at 50Hz which is why the 25kV standard didn't really go anywhere until after the war when mercury arc and silicon rectifiers became available in practical packaging.

EDIT:
Such a motor will not look like a "normal" series wound Universal motor but I believe it would be feasible if you had a way to switch from series winding to a seperately excited AC source to enable braking. Such a source would be tapped directly from an auxiliary winding on the main transformer.

 

[HarleyDavidson]

Didn't 508's used to have rheostatic braking when they first appeared?

 

[507 001]

They still do on Merseyside!

 

[Juniper Driver]

Regen braking on 444/450/458/459 but it used to be Rheostatic.Actually I dont think it was working on 458536+458531 the other day.Friction brake operating at all speeds.

 

[edwin_m]

Regen braking on 444/450/458/459 but it used to be Rheostatic.Actually I dont think it was working on 458536+458531 the other day.Friction brake operating at all speeds.

444s and 450s were delivered with the capability to regenerate but it was disabled by software tweaks and just to make sure a whacking great diode on the way from the shoegear to the traction packages. When Network Rail finally got over the technical and safety concerns and permitted regeneration on the third rail network, it was relatively easy to enable it on these units. I believe the situation with DC Electrostars and Junipers was similar but no diode involved. Shame it didn't happen a few years earlier as it might have saved a bit on the power supply upgrades!

Once trains with three-phase drives were operating, allowing them to regenerate on AC was much easier than on DC and all units capable of doing so have been regenerating on the 25kV network for a decade or so. This only partly explains the Tardis-like noises some of them emit.