Ask me one on sport! Seriously, on the 769, the engines aren't on the same vehicles as the traction motors whilst on locos, the engines are adjacent to the traction motors. This means that the engines are heard first and last as a 769 passes whist the traction motors are closest to the observer when the engines are at a distance.How is it that you hear the engines and traction motors on a 769, but only the engines on a diesel-electric locomotive?
I think the answer is almost completely down to the relative location of the noise sources - the traction inverters and motors are difficult (but not impossible) to hear on a 22x, but can be heard quite prominently in parts of and 80x.How is it that you hear the engines and traction motors on a 769, but only the engines on a diesel-electric locomotive?
According to RailEngineer 2 engines giving 780kW but after stripping off losses supplying 550kW to the traction motors - so over half (just about) the max output of the motors, the article draws comparisons to the 150 (are they about 426 kW?)Just to refresh my memory how many 522bhp engines does a 4 car unit have to propel 140tons plus engines and fuel around. For comparison a class 319 has around 1330hp continuous hp (more for starting) installed.
Hmm perhaps shortening them to lighter 3 car may have been a better idea.According to RailEngineer 2 engines giving 780kW but after stripping off losses supplying 550kW to the traction motors - so over half (just about) the max output of the motors, the article draws comparisons to the 150 (are they about 426 kW?)
then you'd need to attempt the impossible task of relocating anciliaries from the trailer vehicle you're removing. I'd have preferred a pair of more powerful engines. I believe that Brush would have done just that if they could have been shoe-horned in place, but the 522BHP unit fits....Hmm perhaps shortening them to lighter 3 car may have been a better idea.
That's impossible. A lot of vital auxiliary equipment is under the intermediate trailer. Even an all-electric 319 cannot run with a carriage missing.Hmm perhaps shortening them to lighter 3 car may have been a better idea.
Scotrail managed to shorten there 321s so 319s must be different.That's impossible. A lot of vital auxiliary equipment is under the intermediate trailer. Even an all-electric 319 cannot run with a carriage missing.
The 796 would have less horsepower per car than a 150, but the electric transmission should give it better low-end acceleration.
Wasn't all of this explained in an earlier thread?Perhaps brush should have used 321's
The 319s were 'available' it's true, but the others weren't suitable (see post #2359).Only problem being that Brush's customer was Porterbrook, who only had 319s available. Their 455s (when they come available in a year or so's time) will be ripe for shortening to 3 car.
Don't the 317-322 excluding 319 have phase angle control rather than tap changers?Wasn't all of this explained in an earlier thread?
The MKII ac EMUs (classes 317-322) have a common traction design, i.e. transformer/rectifier set to produce a motor supply of up to 750VDC (nominal). The motors are conventional DC types so can be controlled by varying the input voltage level. The normal method is to have a tapped transformer and switch between those taps to vary the (low) ac voltage fed to the rectifiers. this gives a step changing DC feed for the motors. Tap changing on transformers means that there is no need for further equipment to vary the voltage applied to the motors. The arrangement will only work for ac though.
The class 319s are different from the other MKIII ac EMUs because they are required to run on 750VDC 3rd rail or 25kV ac. It was decided to incorporate electro-rheostatic braking in the 319s with a system that would work on both types of supply. This required a common motor supply rail for both power supplies. Instead of using resistors, solid state DC-DC converters were chosen, allowing integrated wheelspin and braking to be included. The space required for this early electronics hardware was not available under the floors of the pantograph/motor car so it had to be accommodated under the trailer.
The coaches are organised thus:
DMSO (or DTCO) - minor auxiliaries including compressorso as you can see, the driving end cars are the only ones with enough room to mount a motor/generator/fuel/exhaust system
MSO - pantograph, transformer & motor bogies
TSO - DC-DC traction controller
DMSO - minor auxiliaries including compressor
For the record, the other MKIII ac EMUs pack all of the major hardware into the MSO as the DC-DC unit is not required, so they can run as 3-car units if required.
Special working arrangements take place for high speed testing work. The signalling at Quorn is set for sighting and braking for 60mph (though I'm sure a modern unit would be fine at 75mph) and thus only Loughborough and Rothley boxes generally open to turn the train round unless there's an operational reason to use the others (points required etc) in which case they function more as a groundframe.Slightly OT but if my eyes weren't deceiving me, how was the unit able to pass all the signals at Danger ??
Thyristor or phase angle control uses the original type of thyristor, which turns on and acts as a diode after voltage is applied to its "gate" terminal but cannot be turned off until the current through the main circuit reverses. The thyristors replace the diodes in the rectifier and are triggered earlier or later during the relevant phase of the AC cycle to vary the amount of time the motors are getting current. Hence the transformer just produces the same secondary voltage all the time with no tap changer. The name "phase angle" comes from the way AC is viewed as a rotating vector so the position within the phase can be described by an angle - one of many ways engineers introduce maths to make an apparently simple concept complicated...thyristor control makes transformer tap-changing redundant.
It's not impossible but it would require a lot of work to be done which means if a TOC wants 3 car EMUs, then other types of EMU are a more cost effective option.That's impossible. A lot of vital auxiliary equipment is under the intermediate trailer. Even an all-electric 319 cannot run with a carriage missing.
Perhaps for any future conversions the soon to be surplus I believe Renautus retractioned 321s or the very powefull 323s may be a better choice. AC motors and IGBT electrics.It's not impossible but it would require a lot of work to be done which means if a TOC wants 3 car EMUs, then other types of EMU are a more cost effective option.