That's fine, providing it leaves Bolton not more than 3 minutes late, or there are other traffic issues on the line requiring some catch-up.
Very likely I imagine. The 769 that failed on the Rhymney line a couple of days ago, where it had to be rescued by 37418. I imagine it succeeded in cancelling several hours worth of Rhymney line trains. It apparently took two hours worth of running at 5mph to get the failure to Rhymney, and that was after the 37was manned up at Rhymney and run light diesel to rescue the failure - in amongst the detonator protection etc
That would be an issue with the choice of the TOC to recover failed trains rather than the fact that any particular type of train might fail sometimes.
I heard about that. Was the reason the 37 could only go at 5mph to do with the 37 being too heavy for the track or the 769 having failed? I suspect part of Northern’s decision to run 769s to Southport (and not somewhere like Rose Hill Marple with a single platform) is that as well as running mostly under the wires, there is the platform capacity at Southport for a failed unit to be stabled until they get round to moving it.
The Diesel engine is supposed to emulate a relatively poor 3rd rail supply. A 769 can reach 75mph on Diesel but full power is not available to it for acceleration. Once it reaches Bolton and has access to all its power, it can accelerate at the same rate as a 319.
I would expect the gensets are rated for a nominal 750VDC output to the bus bit are current limited. We know that during development testing, there were issues with each generator sensing the voltage rise of the other and backing off, causing a sustained 'hunting'. The regulation of the engines was changed to prevent this.
If this was a totally new design I expect the electronics controlling the motors would talk to those controlling the gensets, to limit the power consumption to within the maximum provided by the generators when in diesel mode, and probably also limit it to a lower value if only one generator was running. However, in this case I suspect they last thing they wanted to do was tinker with the 1980s electronics and software of the 319, so would have attempted to make the diesels emulate the third rail and if the traction system demanded too much power it would be restricted by the reduction in bus voltage.
The 319s would need low voltage detection anyway so maybe that is inherent in the as-built traction electronics. i wonder how much 'software' there would be in the 319s as microprocessors were pretty constrained in the mid-80s and most control of them would be on fusible link PROMs or maybe EPROMs in the form of firmware.
I agree there would be some sort of voltage detection in the 319, not sure whether it would just shut off completely if it went under the limit or reduce power more gradually as the voltage declined. But that's a bit different from the traction software "knowing" how much power was available and not demanding any more than that.
Since I am unable to experience a 769 at 100mph (and even if I was it would only ever be on electric from Bolton to Salford Crescent), I have been wondering if it would be possible to reach or sustain 100mph given a longer time to accelerate, but no additional power from the engines than a pair of 150s with a top speed of 75mph. Judging by the lack of performance when running on a single engine, I would suspect this is not the case. It is impressive that they can move at all with only a single engine running.
Please tell me there is no 1980s software in use on 319/769s. No wonder they don’t work properly.
Effectively, the older the stock, the more likely it is to behave when running on a low voltage. The 507/508s (with the same DC equipment as 313s) have managed perfectly well with around 400V between the site of Maghull North and Town Green on the Ormskirk line for many years and the 502s before them could handle even less power. The design being a good 10 years newer, I would expect the limit if the 319s as built to be significantly higher. If they were fed 375V from a single Diesel generator, rather than 750V at half current, I would expect them to refuse to move at all.
There were also Motorola 68000s in the Commodore Amiga, Sega Mega Drive and the early Macintosh, before Apple moved to the Power architecture. Much better than any of the Intel rubbish available at the time, which could scarcely power a scientific calculator.
Two other reasons: the 319s have a DC power bus from the driving vehicles to the motor car which the 321s don’t and therefore makes wiring simpler, and second the project is a Porterbrook initiative and they don’t own any 321s.
What's that saying about "a little bit of knowledge"?
The 769s were said to be capable of just over 90mph on diesel and level track. That is feasible given long enough to get to that speed. At that speed, most of the power at the axles is needed for rolling resistance which is generally quite low on fairly modern passenger stock, and of course air resistance - largely determined by the front end cross sectional area and the general smoothness of the rest of the rain. It increases by the square of the speed. Comparing the top speed with a class 150 is OK in terms of rolling and air resistance is OK (assuming you don't mean a 150/2 which with its gangway connection probably has more resistance than the relatively clean 769 frontage. What is different though is the gearing in the transmission, i.e. the 150 is optimised for 75mph maximum which would be at the limit of the peak power band of its diesel engines. The electric motors on the 319s are optimised for 100mph and by adjusting the drive current and controlling the field strength using the traction electronics, they can achieve their top speed from a fixed DC bus. On the 769s, with an electric transmission between the prime power diesel and the motors, there is plenty of scope to keep the diesel engine well within its maximum power band by controlling the excitation on the three phase generators to maximise the power on the DC bus.
Clearly an individual example of an old EE507 motored EMU could run with a much wider range of line voltages than more modern stock, it has simple resistors to limit the current through the motors and as long as there is enough to turn the motors, the train will move. The 4 motors on the 769s draw nearly 250Kw each, and the 750V bus can only supply about 550kW total. If the motors were allowed to draw enough current such that the voltage dropped to half (i.e. your 375kW figure) that implies that unless the generators run into a serious field collape condition, they would be dissipating about 250kW imnternally as pure resistive losses. Also the auxiliary supplies would also suffer severely.
They probably would have been largely eliminated by now but with the pandemic there has been all sorts of disruption that has not only prevented much of the mileage accumulation to happen but also, when any issues are identified, the appropriate maintenance and/or engineering resource may not have been available so there has been little opportunity to clear down probems satisfactorily.
I understand the DC power bus thing "43096" but I understand Wabtec have had to install the other power bus anyway, so presumably it would be possible even though obviously necessary, to fit the power bus(es) to a 321.
