Current Limit Index

[paulkidger]

I was watching the Youtube cab view of the Seaford to Brighton line and noted a restriction that line has a CLI of 8 and that trains with a CLI greater than 4 must keep to Series operation. Now, I can understand the restriction and the need to keep in Series, but how does the particular CLI equate to power demands (in kW) of the particular train. Typically, what is the maximum speed of running in Series. i presume that this will vary between types, hence 'typically' becomes the crucial word. Thanks in advance

 

[D365]

This sounds more like a question about DC-motored rolling stock?

 

[hexagon789]

I was watching the Youtube cab view of the Seaford to Brighton line and noted a restriction that line has a CLI of 8 and that trains with a CLI greater than 4 must keep to Series operation. Now, I can understand the restriction and the need to keep in Series, but how does the particular CLI equate to power demands (in kW) of the particular train. Typically, what is the maximum speed of running in Series. i presume that this will vary between types, hence 'typically' becomes the crucial word. Thanks in advance

Running in 'series' would only apply with the older Camshaft-control 'slammers' EMUs, though normally where such restrictions carried into the 2000s, it was simply updated to "Notch 2" on modern EMUs.

On Electrostars, it is quite possible to achieve 80mph in Notch 1 I understand, possibly more. So Notch 2 would likely be sufficient for at least 90mph if not 100mph, assuming each Notch is an even 25% increment of 'power'.

On the older Camshaft units, many had a 'Series only' switch, which would prevent the camshaft progressing beyond Full Series.

Alternatively, not going beyond Notch 2 would accomplish the same thing. I believe Full Series is enough for a balancing speed on the level of about 60mph for 90mph units.

 

[paulkidger]

Running in 'series' would only apply with the older Camshaft-control 'slammers' EMUs, though normally where such restrictions carried into the 2000s, it was simply updated to "Notch 2" on modern EMUs.

On Electrostars, it is quite possible to achieve 80mph in Notch 1 I understand, possibly more. So Notch 2 would likely be sufficient for at least 90mph if not 100mph, assuming each Notch is an even 25% increment of 'power'.

On the older Camshaft units, many had a 'Series only' switch, which would prevent the camshaft progressing beyond Full Series.

Alternatively, not going beyond Notch 2 would accomplish the same thing. I believe Full Series is enough for a balancing speed on the level of about 60mph for 90mph units.

Thanks. When you think about it, with modern electronic motor controls, there is no need for the Series/Parallel option so I can see that this restriction is only valid for the older camshaft controlled stock and a 'Notch maximum' has taken its place. Thanks for the typical speeds. 60mph would seem more than adequate for the Seaford branch.

This sounds more like a question about DC-motored rolling stock?

I guess you could argue the case for it being 'ambidextrous' in either category. My decision was based on the fact that it involved the power supply i.e. Infrastructure rather than the Rolling Stock.

 

[hexagon789]

60mph would seem more than adequate for the Seaford branch.

Linespeed is actually 70mph, at least currently.

I did say 'roughly' 60mph, either way presumably the timetable would've taken any restrictions on acceleration and maximum attainable speed into account.

 

[D7666]

First, current rail index applies only to DC motor EMU on third rail in SR zone.

The only such EMU left operational in that zone are 313.

456s and Southern 455s were the last previous types to go (SWT 455s retractioned with AC motors).

IGNORING things like Reps and 442s and 73s as bringing these in will only exponentially confuse matters :

In /very/ simple terms, the current rail index was count 1 for every EE507 motor in the train. Or, if you like, every coach in the train.

Hence a 4car = index 4 as /default/ types 4EPb 4Vep 4Cig etc had 4 motors - 319s were also nominally 4.

These operational values are at 675 (not 750) V DC at the third rail. Indeed all SR vaues quoted in the spotting books are 675 not 750 V.

In terms of kW, all such EMU operate with a current limit relay. If you want to know the maximum kW, power = volts x amps - it is 675 V x the current relay setting in Amp. I /think/ it is 400 A. So 675 V x 400 A = 270 kW max per motor.

Yes this is much greater than the nominal 250 hp quoted for an EE507 motor, but this is how DC EMU work, and perform so well, they can output much more power short term than the stated "trainspotter book" ratings.

In series only, it means 2 motors in series in SR EMU set up, so 135 kW per motor, much less than the nominal 250 hp. A 4car EMU would be maximum 4 x 135 = 540 kW in series only.

442 Reps 73s 71s 74s anything else not EE507 fitted have their own sums to do; each class unique in this respect.

None of this applies to AC motor EMU, which 377 375 450 etc etc are. These do not have conductor rail indices.

They work in very different ways, and, depending on who made it and when, there are differening software controls on current on the traction packs. Some of these (well for 700s at least) are activated by GSM by location. Not sure anyone could give a definitive statement.

The default 'country area' current is (I think) 4000 A, but, places like Seaford and Lymington, distance from substation makes things locally different; not sure the actual figures at these locations are in the public domain.


If I have got some values wrong, the principle is the same when someone else comes along and gives the right values.

 

[paulkidger]

First, current rail index applies only to DC motor EMU on third rail in SR zone.

The only such EMU left operational in that zone are 313.

456s and Southern 455s were the last previous types to go (SWT 455s retractioned with AC motors).

IGNORING things like Reps and 442s and 73s as bringing these in will only exponentially confuse matters :

In /very/ simple terms, the current rail index was count 1 for every EE507 motor in the train. Or, if you like, every coach in the train.

Hence a 4car = index 4 as /default/ types 4EPb 4Vep 4Cig etc had 4 motors - 319s were also nominally 4.

These operational values are at 675 (not 750) V DC at the third rail. Indeed all SR vaues quoted in the spotting books are 675 not 750 V.

In terms of kW, all such EMU operate with a current limit relay. If you want to know the maximum kW, power = volts x amps - it is 675 V x the current relay setting in Amp. I /think/ it is 400 A. So 675 V x 400 A = 270 kW max per motor.

Yes this is much greater than the nominal 250 hp quoted for an EE507 motor, but this is how DC EMU work, and perform so well, they can output much more power short term than the stated "trainspotter book" ratings.

In series only, it means 2 motors in series in SR EMU set up, so 135 kW per motor, much less than the nominal 250 hp. A 4car EMU would be maximum 4 x 135 = 540 kW in series only.

442 Reps 73s 71s 74s anything else not EE507 fitted have their own sums to do; each class unique in this respect.

None of this applies to AC motor EMU, which 377 375 450 etc etc are. These do not have conductor rail indices.

They work in very different ways, and, depending on who made it and when, there are differening software controls on current on the traction packs. Some of these (well for 700s at least) are activated by GSM by location. Not sure anyone could give a definitive statement.

The default 'country area' current is (I think) 4000 A, but, places like Seaford and Lymington, distance from substation makes things locally different; not sure the actual figures at these locations are in the public domain.


If I have got some values wrong, the principle is the same when someone else comes along and gives the right values.

Thanks for that reply, especially the significance of the CRI. Yes I take on the difference between the short term and continuous ratings of the motors. Re the AC motored and electronically controlled units, I would imagine that they have some form of current rating for reasons of the long branch supply situations. If I remember correctly the losses are I^2 *R (Square of the current x the resistance) and with the long branches the 'R' must become significant....Steel is a pretty poor conductor. Actually 750V is a very convenient Voltage since 1 amp = 1 HP.

 

[D7666]

Thanks for that reply, especially the significance of the CRI. Yes I take on the difference between the short term and continuous ratings of the motors. Re the AC motored and electronically controlled units, I would imagine that they have some form of current rating for reasons of the long branch supply situations. If I remember correctly the losses are I^2 *R (Square of the current x the resistance) and with the long branches the 'R' must become significant....Steel is a pretty poor conductor. Actually 750V is a very convenient Voltage since 1 amp = 1 HP.

Spot on with I^2R.

The /general/ third rail current limits per train are (I think) 4000 / 5000 / 6000 Amp for country / outer suburban / inner suburban areas but not easy to align with track maps for OCD trainspotter precision needs.

6800 A is the absolute maximum; the erstwhile DC Eurostar routes, local areas around depots, and very busy locations have this value.

No idea how this functions on restricted routes like Seaford or Lymington.

Weymouth is dealt with somewhat klunkily by the Power Control Room counting the number of trains in the area whenver there is out of course running or additionals.

700/1 are capped at 4000 5000 6000 A for those three areas; 700/0 are capped at 3000 3750 4500 A. 700s have some of the highest values. 700s switch settings by GSM location signal. (This is DC of course; 25 kV has nothing to do with it.)

375/377s are complexicated. AFAIK from data I was given nearly 20 years ago while things were in planning = 750 A per pack, or, if you prefer, per Bo bogie (= per motor coach) so:

3car 1500 A
4car 2250 A

But then it gets complexicated there upwards as the software does load sharing with multipled units.

One example you can make up a 12car from 4x3 (8 Bo bogies) or 3x4 (9 Bo bogies) *** but either way the train is capped at 4500 A. At least, it was 20 years ago; I believe it may be greater now.

Other types no complete data.

*** well being pedantic 5+4+3 = 12 too but not sure they ever would do that.

 

[paulkidger]

Spot on with I^2R.

The /general/ third rail current limits per train are (I think) 4000 / 5000 / 6000 Amp for country / outer suburban / inner suburban areas but not easy to align with track maps for OCD trainspotter precision needs.

6800 A is the absolute maximum; the erstwhile DC Eurostar routes, local areas around depots, and very busy locations have this value.

No idea how this functions on restricted routes like Seaford or Lymington.

Weymouth is dealt with somewhat klunkily by the Power Control Room counting the number of trains in the area whenver there is out of course running or additionals.

700/1 are capped at 4000 5000 6000 A for those three areas; 700/0 are capped at 3000 3750 4500 A. 700s have some of the highest values. 700s switch settings by GSM location signal. (This is DC of course; 25 kV has nothing to do with it.)

375/377s are complexicated. AFAIK from data I was given nearly 20 years ago while things were in planning = 750 A per pack, or, if you prefer, per Bo bogie (= per motor coach) so:

3car 1500 A
4car 2250 A

But then it gets complexicated there upwards as the software does load sharing with multipled units.

One example you can make up a 12car from 4x3 (8 Bo bogies) or 3x4 (9 Bo bogies) *** but either way the train is capped at 4500 A. At least, it was 20 years ago; I believe it may be greater now.

Other types no complete data.

*** well being pedantic 5+4+3 = 12 too but not sure they ever would do that.

Thanks again. My experience is in industry with electrical drives of up to 1000 kW driving items such as pumps, fans and compressors. To me the currents flowing in the DC lines are horendous. Likewise the motor duty seems incredible. To me anything over about 50 kW should be limited to 4 starts per hour so I guess the DC traction motors pay a lot of attention to dissipating heat, especially from starts. Regarding the infamous 'I squared R' losses, I think I first came across this in my a level physics many years ago. When the Bournmouth electrification was being planned, I remember seeing an item in New Scientist covering the choice between an extension of the DC or grasping the nettle and going for 25 kV AC. It was titled something like £.s.d wins over Ohm's Law (It was in pre decimal days).....Now I think that more attention had been paid to Ohm's Law.

 

[Taunton]

Weymouth is dealt with somewhat klunkily by the Power Control Room counting the number of trains in the area whenever there is out of course running or additionals.

Weymouth, which I have regular experience of, must nevertheless have some considerable current draw on the 1in50 bank from there up to Dorchester. You don't get sparkling uphill performance, but it's better than the GWR diesels growling up there. I do recall that for busy moments there (like at the Olympics) doubled-up 10-coach 444s are not acceptable, and doubled 8-coach 450s are substituted on the service instead, apparently for current limit reasons.

I did once read that the line onward from Dorchester to Moreton was singled at electrification, as much to prevent too many electric trains being in section as to save on track maintenance costs.

 

[D365]

Now I think that more attention had been paid to Ohm's Law.

You're right, but apparently the experts never know best.

(sarcasm, obviously!)

 

[paulkidger]

You're right, but apparently the experts never know best.

(sarcasm, obviously!)

Fortunately, the electrification project over-ran so steam prevailed during the time I was at Southampton in 1965/66.

 

[notadriver]

Spot on with I^2R.

The /general/ third rail current limits per train are (I think) 4000 / 5000 / 6000 Amp for country / outer suburban / inner suburban areas but not easy to align with track maps for OCD trainspotter precision needs.

6800 A is the absolute maximum; the erstwhile DC Eurostar routes, local areas around depots, and very busy locations have this value.

No idea how this functions on restricted routes like Seaford or Lymington.

Weymouth is dealt with somewhat klunkily by the Power Control Room counting the number of trains in the area whenver there is out of course running or additionals.

700/1 are capped at 4000 5000 6000 A for those three areas; 700/0 are capped at 3000 3750 4500 A. 700s have some of the highest values. 700s switch settings by GSM location signal. (This is DC of course; 25 kV has nothing to do with it.)

375/377s are complexicated. AFAIK from data I was given nearly 20 years ago while things were in planning = 750 A per pack, or, if you prefer, per Bo bogie (= per motor coach) so:

3car 1500 A
4car 2250 A

But then it gets complexicated there upwards as the software does load sharing with multipled units.

One example you can make up a 12car from 4x3 (8 Bo bogies) or 3x4 (9 Bo bogies) *** but either way the train is capped at 4500 A. At least, it was 20 years ago; I believe it may be greater now.

Other types no complete data.

*** well being pedantic 5+4+3 = 12 too but not sure they ever would do that.

I wonder if the current limit is a little lower than 4500A - 4000A might be about right. I vaguely recall the performance of 3*3 car sets coupled together and it wasn’t great. Probably similar to 2*4 cars. But certain odd formations did perform well. 4+3 cars would be seriously quicker than a 4+4 - and 4+4+3 (11 car) would leave a 12 car (4+4+4) for dust. That’s for 375s.

444s seem to be the slowest accelerating 3rd rail units in the country - taking 90 seconds to reach 60 mph. A cross country diesel powered voyager is positively amazing by comparison. Not sure what they are like in multiple - a 12 car (6+6) class 395 is extremely sluggish on DC third rail where most of its journey tends to be.

Then there are differences between sub classes. 375/9 tend to be sluggish compared to 375/8 but that’s another story.

 

[swt_passenger]

444s seem to be the slowest accelerating 3rd rail units in the country - taking 90 seconds to reach 60 mph. A cross country diesel powered voyager is positively amazing by comparison. Not sure what they are like in multiple - a 12 car (6+6) class 395 is extremely sluggish on DC third rail where most of its journey tends to be.

Then there are differences between sub classes. 375/9 tend to be sluggish compared to 375/8 but that’s another story.

The 444s have the same traction packages and motors fitted as 450s, but AIUI they operate with a higher maximum power limit than 450s, so that a 10.444 has something approaching the same total as a 12.450, but not quite enough. It was posted a while ago what the exact figures were, but I can never find it again.

There was also a post within the last year or two about work going on to allow an increase to the 444s power limit to give a 10.444 identical performance to 12.450.

 

[Richard Scott]

In series only, it means 2 motors in series in SR EMU set up, so 135 kW per motor, much less than the nominal 250 hp. A 4car EMU would be maximum 4 x 135 = 540 kW in series only.

If current was still 400A through each motor but guessing it isn't as double resistance when in series so current halved. As Voltage also half across each motor power would be reduced by four times.

 

[D7666]

If current was still 400A through each motor but guessing it isn't as double resistance when in series so current halved. As Voltage also half across each motor power would be reduced by four times.

Motors when "in series" are in two series-parallel groups they are not 4 motors all in series; when "in parallel" they are all in parallel.

 

[Richard Scott]

Motors when "in series" are in two series-parallel groups they are not 4 motors all in series; when "in parallel" they are all in parallel.

I know hence why I've put what I've put as run as two series pairs in parallel so voltage halved across each motor (would be a quarter if all four in series) and I was assuming current halved due to double resistance. Hence output power is a quater as 0.5 x 0.5 is 0.25.

 

[paulkidger]

First, current rail index applies only to DC motor EMU on third rail in SR zone.

The only such EMU left operational in that zone are 313.

456s and Southern 455s were the last previous types to go (SWT 455s retractioned with AC motors).

IGNORING things like Reps and 442s and 73s as bringing these in will only exponentially confuse matters :

In /very/ simple terms, the current rail index was count 1 for every EE507 motor in the train. Or, if you like, every coach in the train.

Hence a 4car = index 4 as /default/ types 4EPb 4Vep 4Cig etc had 4 motors - 319s were also nominally 4.

These operational values are at 675 (not 750) V DC at the third rail. Indeed all SR vaues quoted in the spotting books are 675 not 750 V.

In terms of kW, all such EMU operate with a current limit relay. If you want to know the maximum kW, power = volts x amps - it is 675 V x the current relay setting in Amp. I /think/ it is 400 A. So 675 V x 400 A = 270 kW max per motor.

Yes this is much greater than the nominal 250 hp quoted for an EE507 motor, but this is how DC EMU work, and perform so well, they can output much more power short term than the stated "trainspotter book" ratings.

In series only, it means 2 motors in series in SR EMU set up, so 135 kW per motor, much less than the nominal 250 hp. A 4car EMU would be maximum 4 x 135 = 540 kW in series only.

442 Reps 73s 71s 74s anything else not EE507 fitted have their own sums to do; each class unique in this respect.

None of this applies to AC motor EMU, which 377 375 450 etc etc are. These do not have conductor rail indices.

They work in very different ways, and, depending on who made it and when, there are differening software controls on current on the traction packs. Some of these (well for 700s at least) are activated by GSM by location. Not sure anyone could give a definitive statement.

The default 'country area' current is (I think) 4000 A, but, places like Seaford and Lymington, distance from substation makes things locally different; not sure the actual figures at these locations are in the public domain.


If I have got some values wrong, the principle is the same when someone else comes along and gives the right values.

Using your reply as a route to a further question, Are Mercury Arc rectifiers still in use anywhere on the system? At one time I thought these outdated but the more I read about them, the more I can see their virtues.

 

[D7666]

Using your reply as a route to a further question, Are Mercury Arc rectifiers still in use anywhere on the system? At one time I thought these outdated but the more I read about them, the more I can see their virtues.

None that I know of, but that is an off the top of my head reply and TBH never thought of it before.

At least if I say none, you can be sure IF there are any left then someone will be along to correct it. Whereas answers like "don't know" don't ellicit a response.

 

[SolomonSouth]

444s seem to be the slowest accelerating 3rd rail units in the country - taking 90 seconds to reach 60 mph. A cross country diesel powered voyager is positively amazing by comparison. Not sure what they are like in multiple - a 12 car (6+6) class 395 is extremely sluggish on DC third rail where most of its journey tends to be.

You sure about that mate? I would guess that the old Class 507s/508s are slower.

I'd also be surprised if the 319/769 on third rail was faster than a 444, but correct me if I'm wrong...