Porterbrook Cl.769 'Flex' trains from 319s, initially for Northern

[FenMan]

For the same routes as 319 I imagine a conversion course would be fairly meaty in terms of driving a DMU vs EMU, but not unworkable since the cab would be fairly similar otherwise. The difficulty is that the main point of the 769s is to operate on routes EMUs can't, thus you'd be adapting Pacer and Sprinter drivers. That's probably a fairly lengthy training course. I don't know how similar 150s and 319s are in that regard.

Class 165/166 drivers too.

 

[Elecman]

Well they must have recently trained ex-sprinter/pacer drivers on the 319s when they started taking ex-Thameslink trains at Allerton for the Chat Moss electrified lines. So they could maybe do a mix and match with a short conversion course for them on the 369s whilst taking on fresh drivers for some of the all-electric diagrams.

Assume 369 is a typo for 769?

 

[AM9]

Your bad what?

Horrible, horrible, horrible imported US phrase that should never be used!

Exactly my view.

Assume 369 is a typo for 769?

Damn, done it again! Thanks, yes it is.

 

[Lemmy99uk]

Damn, done it again! Thanks, yes it is.

Your bad

 

[Greybeard33]

So it's more a question of the electric transmission at low speeds drawing relatively little power from the diesel and alternator or from the traction supply. At similar low speeds a hydraulic transmission draws much more power from the diesel engine, most of which goes to heat in the torque convertor.

The 769 has inherited the 319's series wound DC commutator traction motors. This type of motor delivers a high starting torque (=tractive effort) but, like a hydraulic torque converter, it is very inefficient at low speeds. Nearly all the input power is wasted heating up the windings (copper losses). As speed increases, more power is converted to useful mechanical work and efficiency improves.

The fixed motor gear ratio has to be a compromise. If the 319 were regeared for a 75mph top speed instead of 100mph, acceleration and efficiency at lower speeds would improve.

Hybrid transmissions in road vehicles get much of their efficiency gains from regenerative braking. Energy recovered during braking is stored in a battery then fed back to the motor during acceleration, so enabling a smaller engine to be used. The 769 does not have regenerative braking or battery storage.

I do not have figures, but I would be surprised if the average overall efficiency of the 769 electric transmission (generators + traction control electronics + motors) is any better than that of the Voith hydromechanical transmission in a 15x, on a typical Northern service. The ZF 6-speed mechanical transmission of the 195 should have much lower losses.

On the other hand, an electric transmission does enable the diesel engine to run at its most efficient speed all the time.

 

[Jonny]

I do not have figures, but I would be surprised if the average overall efficiency of the 769 electric transmission (generators + traction control electronics + motors) is any better than that of the Voith hydromechanical transmission in a 15x, on a typical Northern service. The ZF 6-speed mechanical transmission of the 195 should have much lower losses.

On the other hand, an electric transmission does enable the diesel engine to run at its most efficient speed all the time.

Perhaps the diesel-electric combo is pretty efficient compared to older diesel-hydraulic drives - but I would expect that the variability of ratio associated with six gears would help to keep a diesel engine near its most efficient point for a wide variety of speeds as well.

 

[big all]

The 769 has inherited the 319's series wound DC commutator traction motors. This type of motor delivers a high starting torque (=tractive effort) but, like a hydraulic torque converter, it is very inefficient at low speeds. Nearly all the input power is wasted heating up the windings (copper losses). As speed increases, more power is converted to useful mechanical work and efficiency improves.

The fixed motor gear ratio has to be a compromise. If the 319 were regeared for a 75mph top speed instead of 100mph, acceleration and efficiency at lower speeds would improve.

Hybrid transmissions in road vehicles get much of their efficiency gains from regenerative braking. Energy recovered during braking is stored in a battery then fed back to the motor during acceleration, so enabling a smaller engine to be used. The 769 does not have regenerative braking or battery storage.

I do not have figures, but I would be surprised if the average overall efficiency of the 769 electric transmission (generators + traction control electronics + motors) is any better than that of the Voith hydromechanical transmission in a 15x, on a typical Northern service. The ZF 6-speed mechanical transmission of the 195 should have much lower losses.

On the other hand, an electric transmission does enable the diesel engine to run at its most efficient speed all the time.

i dont know why they dont make a version with a large capacity traction battery like the 230 and diesel the other end then anything less than a 50%/50 would be more efficient
with the engine charging the battery continuously iff required would mean at say 45% powering you would have more than the combined power for starting and until the battery goes flat then single engine
until both braking [regenerative ]and engine charging plus boosts from overhead or third rail
a perfect choice for gatwick to reading with perhaps 40% electrified

 

[AndrewE]

i dont know why they dont make a version with a large capacity traction battery like the 230 and diesel the other end then anything less than a 50%/50 would be more efficient
with the engine charging the battery continuously if required would mean at say 45% powering you would have more than the combined power for starting and until the battery goes flat then single engine
until both braking [regenerative ]and engine charging plus boosts from overhead or third rail
a perfect choice for gatwick to reading with perhaps 40% electrified

Perhaps they will, but they still have a hurdle to jump: getting the simple Diesel / Electric version to work reliably on test and then getting it established in fleet service.
It might be a goer though, and possibly (hopefully) a simpler upgrade to do than the development we are currently waiting for...

 

[Jonny]

Also, apparently a "Desiro" is planned as the base for a battery-flex.

A 350/2, apparently, according to Porterbrook (the ROSCO that owns, as well as other trains, the 319s and 769s)

https://www.porterbrook.co.uk/news/...unces-batteryflex-in-green-great-britain-week
Porterbrook announces BatteryFLEX in Green Great Britain Week

Porterbrook has completed an engineering assessment that makes a positive case for the conversion of one of the UK’s most reliable trains into a battery/electric bi-mode.

The class 350 Electric Multiple Unit is Britain’s most reliable train, with Porterbrook’s 350/2 version recording 100,420 Miles per Technical Incident (Moving Annual Average).

With the addition of the latest battery technology, Porterbrook is confident that the 350/2 BatteryFLEX would be able to match, or outperform, diesel trains on existing non-electrified routes, particularly in key corridors across the North of England.
(article continues)

 

[swt_passenger]

Also, apparently a "Desiro" is planned as the base for a battery-flex.

A 350/2, apparently, according to Porterbrook (the ROSCO that owns, as well as other trains, the 319s and 769s)

We had a thread about it at the time it was first announced:
https://www.railforums.co.uk/threads/class-350-batteryflex.171906/

 

[edwin_m]

The 769 has inherited the 319's series wound DC commutator traction motors. This type of motor delivers a high starting torque (=tractive effort) but, like a hydraulic torque converter, it is very inefficient at low speeds. Nearly all the input power is wasted heating up the windings (copper losses). As speed increases, more power is converted to useful mechanical work and efficiency improves.

Do you have a source for this?

At low speed the motor has very low resistance so applying the full voltage would result in very high currents and overheating. Hence the voltage across the motor must be kept low. On a traditional DC traction system this is done by switching in resistance, which is inefficient but is a feature of the control system not the motor. On an AC train with DC motors the voltage is limited by a tap changer or by pulse width modulation. I've never heard DC-motored units having heat-related restrictions on low speed running, unless they also have traditional DC control systems which may not be able to run indefinitely with resistance in circuit.

 

[Mogster]

Are the Northern 319 units being modded with air conditioning or is that the GWR units only?

https://www.railengineer.uk/2018/09/27/bi-mode-good-tri-mode-better/

 

[AndrewE]

Are the Northern 319 units being modded with air conditioning or is that the GWR units only?

https://www.railengineer.uk/2018/09/27/bi-mode-good-tri-mode-better/

Please don't! We don't need it that much, the airflow from opening windows is more refreshing and it's something more to go wrong - and failed air con with hardly any openable windows is the worst of all worlds. If it ain't broke then don't fix it.

 

[Mogster]

There’s plenty of opening windows, unless they choose to bolt them shut... Is modern AC really that unreliable? The problems seem to be mostly on older units like 158s.

Having travelled in overcrowded 150, 142, 185 carriages pretty much daily my experience is that I’d much rather have it than not. It reduces moisture inside the carriages on wet days as a side effect also, stops condensation covering and running down the windows and onto the floor. This is 2018... every train should have AC.

 

[coppercapped]

This is 2018... every train should have AC.

Not for much longer...!

 

[Mogster]

Heh, lets keep the abreviation to air con then to avoid any confusion

 

[samuelmorris]

I very rarely experience A/C problems on modern stock that's had it from new. It generally seems to work fine the vast majority of the time. Old refurbished stock, however, has a reputation for unreliable air conditioning, the 321s which are the closest facsimile to this project, have apparently been very problematic. That sets a precedent for what you might expect from 769s fitted with A/C.

 

[Bornin1980s]

I very rarely experience A/C problems on modern stock that's had it from new. It generally seems to work fine the vast majority of the time. Old refurbished stock, however, has a reputation for unreliable air conditioning, the 321s which are the closest facsimile to this project, have apparently been very problematic. That sets a precedent for what you might expect from 769s fitted with A/C.

Looks like you weren't on the first IET run!

 

[Kyle1]

Looks like you weren't on the first IET run!

Well cold water does cool you down so it technically did do its job...

 

[jimm]

Are the Northern 319 units being modded with air conditioning or is that the GWR units only?

https://www.railengineer.uk/2018/09/27/bi-mode-good-tri-mode-better/

Heh, lets keep the abreviation to air con then to avoid any confusion

No, let's not talk about air conditioning at all - because, like the GWR Class 165s and the Chiltern Class 165s before them, the GWR Class 769s will be fitted with passenger saloon air cooling equipment.

 

[AndrewE]

No, let's not talk about air conditioning at all - because, like the GWR Class 165s and the Chiltern Class 165s before them, the GWR Class 769s will be fitted with passenger saloon air cooling equipment.

That's fine, just please don't do it to the ones for the north of the country. 319s are great (compared with what we have had up to now) if the 769s work properly then they will be an improvement on diesel trains having to run into the centre of our cities (and a battery hybrid version might also be good - as long as it works.) Don't undermine reliability with anything extra that isn't really necessary...

 

[jimm]

Who said anything about air cooling or air conditioning undermining reliability?

While Chiltern fitted sealed windows on its 165s, GWR has retained the hopper windows on its 165s, so they can be unlocked by staff if there is a system fault, not that there seem to be any serious issues in either fleet - whereas I have always had an issue with travelling in coaches with hopper windows open and a howling gale blowing through.

 

[Ken H]

Do you have a source for this?

At low speed the motor has very low resistance so applying the full voltage would result in very high currents and overheating. Hence the voltage across the motor must be kept low. On a traditional DC traction system this is done by switching in resistance, which is inefficient but is a feature of the control system not the motor. On an AC train with DC motors the voltage is limited by a tap changer or by pulse width modulation. I've never heard DC-motored units having heat-related restrictions on low speed running, unless they also have traditional DC control systems which may not be able to run indefinitely with resistance in circuit.

resistors to control starting current were made obsolete by choppers. But this started the whole issue of power electronics interfering with signalling. but replacing contactors and relays with solid state does improve reliability. And less electricity used (I think)

 

[Bornin1980s]

No, let's not talk about air conditioning at all - because, like the GWR Class 165s and the Chiltern Class 165s before them, the GWR Class 769s will be fitted with passenger saloon air cooling equipment.

Is cheaper 'air conditioning' in cars technically closer to air cooling?

 

[Greybeard33]

At low speed the motor has very low resistance so applying the full voltage would result in very high currents and overheating. Hence the voltage across the motor must be kept low. On a traditional DC traction system this is done by switching in resistance, which is inefficient but is a feature of the control system not the motor. On an AC train with DC motors the voltage is limited by a tap changer or by pulse width modulation. I've never heard DC-motored units having heat-related restrictions on low speed running, unless they also have traditional DC control systems which may not be able to run indefinitely with resistance in circuit.

I did not mean that the full supply voltage is applied to the motor at low speed. Like the older switched resistor system, the 319/769 traction controller (GTO thyristor chopper) drops the motor voltage to a low value when starting, in order to limit the current to that needed for the required torque, per the driver-selected "notch". This avoids motor overheating or wheelspin, but with lower losses than switched resistors.

When the motor is stalled, its efficiency is zero. The electrical power it absorbs (motor voltage*current) is entirely dissipated as heat in the field and armature windings. As the train accelerates, the motor armature starts to generate a back emf that tends to reduce the current. The controller compensates by increasing the motor voltage to maintain the current and torque, similar to switching out resistance in a traditional controller. With the same current, the resistive heat loss in the windings (I squared R) is still the same, but the motor is absorbing more power due to the higher voltage. This is mainly turned into mechanical shaft power (back emf*current). Therefore the motor efficiency rises progressively with increasing speed.

Once the speed is reached at which the full supply voltage can be switched to the motor, further acceleration causes the motor current to start to fall. The resistive losses then reduce with the square of the current, whereas the power input reduces linearly with current. So motor efficiency continues to increase with speed.

 

[59CosG95]

319443 was moved from Wolverton to Brush earlier this week; I assume it's going in for its 769 conversion works.

 

[edwin_m]

I did not mean that the full supply voltage is applied to the motor at low speed. Like the older switched resistor system, the 319/769 traction controller (GTO thyristor chopper) drops the motor voltage to a low value when starting, in order to limit the current to that needed for the required torque, per the driver-selected "notch". This avoids motor overheating or wheelspin, but with lower losses than switched resistors.

When the motor is stalled, its efficiency is zero. The electrical power it absorbs (motor voltage*current) is entirely dissipated as heat in the field and armature windings. As the train accelerates, the motor armature starts to generate a back emf that tends to reduce the current. The controller compensates by increasing the motor voltage to maintain the current and torque, similar to switching out resistance in a traditional controller. With the same current, the resistive heat loss in the windings (I squared R) is still the same, but the motor is absorbing more power due to the higher voltage. This is mainly turned into mechanical shaft power (back emf*current). Therefore the motor efficiency rises progressively with increasing speed.

Once the speed is reached at which the full supply voltage can be switched to the motor, further acceleration causes the motor current to start to fall. The resistive losses then reduce with the square of the current, whereas the power input reduces linearly with current. So motor efficiency continues to increase with speed.

OK, I understand where you are coming from on this, thanks for the explanation. However I do wonder how significant the heat loss in the motor windings is compared with the various other losses in the movement of the train.

 

[Cardiff123]

Is there actually anymore news/developments on this project? Has testing commenced away from the GCR yet? Considering the first deliveries to Northern are supposed to be early next month and to TfW in February, with only 3 weeks left until the Christmas & New Year shutdown, the lack of any more news since the initial photos & videos of the first unit testing on the GCR is worrying.

Have any further units been tested on the GCR?

 

[Bornin1980s]

I just want to know if there are any more videos.

 

[big all]

I just want to know if there are any more videos.

i have looked quite extensively but can only find the 2 utube off the same clip