ETH/ETS capacity when double heading or T&T

[G-BOAF]

Question, specifically in my mind re the limited ETH index on a 37/4.

When two locos are double heading, can both be connected to ETS of coaching with the respective indexes summed (so a pair of heat 37s would total index of 60)?

 

Alternatively, if operating in T&T mode, could the front loco heat/cool one half of the train, and rear loco the other half (with ETH wires disconnected in the middle, but lighting control RCH jumpers connected to enable through control by guard).

 

Motivation - I'm trying to justify a longer rake than 6 mk2s behind my heated 37, or a 37 railtour without a generator van.

[DY444]

3 hours ago, G-BOAF said:

Question, specifically in my mind re the limited ETH index on a 37/4.

When two locos are double heading, can both be connected to ETS of coaching with the respective indexes summed (so a pair of heat 37s would total index of 60)?

 

Alternatively, if operating in T&T mode, could the front loco heat/cool one half of the train, and rear loco the other half (with ETH wires disconnected in the middle, but lighting control RCH jumpers connected to enable through control by guard).

 

Motivation - I'm trying to justify a longer rake than 6 mk2s behind my heated 37, or a 37 railtour without a generator van.

 

No.  Only one loco can supply ets.  Most ets locomotives had a protection mechanism which stopped them supplying the train if the train circuit was already live.  Iirc the only ones that didn't were the SR classes.

  

There is a real world example of locomotives regularly working trains they couldn't properly supply power to.   The locomotives were the Class 50s and there were special instructions relating to them working trains with an eth index greater than 48 on very cold or very hot days to avoid overloading the somewhat under nourished eth generator.  Nothing I'm aware of about 37/4s working trains with high eth indices though.

[russ p]

1 hour ago, DY444 said:

 

No.  Only one loco can supply ets.  Most ets locomotives had a protection mechanism which stopped them supplying the train if the train circuit was already live.  Iirc the only ones that didn't were the SR classes.

  

There is a real world example of locomotives regularly working trains they couldn't properly supply power to.   The locomotives were the Class 50s and there were special instructions relating to them working trains with an eth index greater than 48 on very cold or very hot days to avoid overloading the somewhat under nourished eth generator.  Nothing I'm aware of about 37/4s working trains with high eth indices though.

 

I was guard on a charter some years back and the generator car packed up. One of the locos was a 37/4 . It was a red hot day and by juggling coaches on and off I managed to keep all 12 cool. Cooling doesn't draw as much load as heating so I had 7 or 8 aircons on at a time and the loco was happy with that. When we did charters with 47s or 57s I would try to have the rear one providing ETG as that gave the front one more traction power.

You did have to be careful not to switch both on. It was possible to switch the rear ETH off from the front loco but not switch it on. Pressing the off button brakes the circuit of the 110v providing circuit which drops all locos out

[45125]

With ETH locos in multi only one can supply ETH. As soon as soon as the ETH is turned on a voltage detection circuit on the other one detects the voltage and via various interlocks will prevent any attempt to turn the ETH on that loco. It was arranged so that the ETH alternator/generator cannot be connected in parallel.. The voltage detection circuit on the non supplying loco also illuminates the ETH on lamp on that loco.

 

Al Taylor 

[Davexoc]

5 hours ago, DY444 said:

There is a real world example of locomotives regularly working trains they couldn't properly supply power to.   The locomotives were the Class 50s and there were special instructions relating to them working trains with an eth index greater than 48 on very cold or very hot days to avoid overloading the somewhat under nourished eth generator.

 

The ETH generator on the class 50s also powered the radiator cooling fan, which took a fair chunk of output.

Like the HST power cars, it notched up the engine rpm when the ETH was switched on.

 

In theory you could split a train in two halves and run ETH from both ends as the interlocking would allow it, and if you had a defective vehicle part way through the train, by disconnecting you would still have the connected portion working. I changed a few jumpers that got ripped out when shunters forgot to disconnect them...

[Simon Bendall]

2 hours ago, Davexoc said:

 

In theory you could split a train in two halves and run ETH from both ends as the interlocking would allow it

 

This was done some years ago when the Caledonian Sleepers were diverted via Manchester, 67 each end to power half the set and jumpers not connected in the middle.

[roythebus1]

The problem on locos supplying ac ETH current is if you connect another loco supplying ac ETH would be the phases not matched.

[Davexoc]

2 hours ago, roythebus1 said:

The problem on locos supplying ac ETH current is if you connect another loco supplying ac ETH would be the phases not matched.

 

Good old bog standard ETH was DC from generators, or third rail on the SR.

AC came about when the HST arrived, powered off an alternator, but LH Mk 3s were still DC.

[Edwin_m]

5 hours ago, Davexoc said:

 

Good old bog standard ETH was DC from generators, or third rail on the SR.

AC came about when the HST arrived, powered off an alternator, but LH Mk 3s were still DC.

The standard spec allowed a wide range of voltages and frequencies from DC upwards on a single phase.  Some coaches were incompatible with Deltics and the original generator 47s (so needed AC?) but these were based on the Western well away from those locomotives.  

 

HSTs had a totally different an incompatible system sending three-phase AC down the train, which avoided the need for rotary converters on the trailers.  

[roythebus1]

We had the original generator 47s at Kings Cross in 1977, they were "quite quick". :) 47 401 etc. Opened up a bit at FP to keep out of the way of Deltics.

Edited March 2 by roythebus1

[45125]

4 minutes ago, Edwin_m said:

The standard spec allowed a wide range of voltages and frequencies from DC upwards on a single phase.  Some coaches were incompatible with Deltics and the original generator 47s (so needed AC?) but these were based on the Western well away from those locomotives.  

 

HSTs had a totally different an incompatible system sending three-phase AC down the train, which avoided the need for rotary converters on the trailers.  

As mentioned previous the supply will parallel up the generating device, which is not good. The voltages will not match as the excitation depends on what the auxiliary supply is requiring as excitation to maintain the battery charge voltage, with an alternator the ETH voltage can vary anywhere between 775v and 1080v depending on the engine speed/excitation level, with a DC generator supply from earlier locos it should be 750v but as these rely on an AVR to regulate this there is a slight delay in the excitation so the voltage fluctuates, think a 50 is 800v. With AC traction the ETH voltage is AC but this fluctuates as the OHL supply fluctuates depending on loading. I know of areas where the OHL dropped to 11kv with the ETH voltage plummeting to almost 540v.

 

 

[roythebus1]

That's a lot of voltage drop fro 25kv to 11kv! My point is that if you have 2 locos that provide single-phase ac ETH, the 2 alternators will not be in phase. I wasn't trained on locos and REPS on the suvvern, just EMU stock but had the basics of what could and couldn't be done when coupling up. Worked on ac electrics at Rugby and diesels out of Kings Cross as secondman. and the Underground.

[45125]

1 hour ago, roythebus1 said:

That's a lot of voltage drop fro 25kv to 11kv! My point is that if you have 2 locos that provide single-phase ac ETH, the 2 alternators will not be in phase. I wasn't trained on locos and REPS on the suvvern, just EMU stock but had the basics of what could and couldn't be done when coupling up. Worked on ac electrics at Rugby and diesels out of Kings Cross as secondman. and the Underground.

There was one area near barks ton when the OHL would drop to around 11kv on a regular basis, first sign that it was dropping was that cab air con would go off.      With alternator it doesn't matter about the out of phase issue, once the supply has been rectified its DC, so when connected two alternators up in parallel DC ends up meeting AC once back through the rectifier. The alternator makes some lovely noises..............

                                                                           

[Davexoc]

11 hours ago, roythebus1 said:

That's a lot of voltage drop fro 25kv to 11kv! My point is that if you have 2 locos that provide single-phase ac ETH, the 2 alternators will not be in phase. I wasn't trained on locos and REPS on the suvvern, just EMU stock but had the basics of what could and couldn't be done when coupling up. Worked on ac electrics at Rugby and diesels out of Kings Cross as secondman. and the Underground.

 

The ETH jumpers were all something DC (anything from about 650v up to 1000v), the variation depending on where they were in the country and what the power source was. AC electrics rectified to DC so partly dependant on how much AC there was, SR from the third rail dependant on the rail voltage which is more prone to voltage drop than AC, or if from a diesel, dependant on engine rpm and load with some sharing the same generator as the traction supply, others seperate generator. Later diesels could have an alternator, but it would be rectified to DC as with only one type of jumper, there had to be a standard throughout the network, and coaches used to run all the way from Scotland to Cornwall with various traction changes en-route.

 

 

[roythebus1]

The ETH voltage is also standard across the UIC railways.

[DY444]

11 hours ago, Davexoc said:

 

The ETH jumpers were all something DC (anything from about 650v up to 1000v), the variation depending on where they were in the country and what the power source was. AC electrics rectified to DC so partly dependant on how much AC there was, SR from the third rail dependant on the rail voltage which is more prone to voltage drop than AC, or if from a diesel, dependant on engine rpm and load with some sharing the same generator as the traction supply, others seperate generator. Later diesels could have an alternator, but it would be rectified to DC as with only one type of jumper, there had to be a standard throughout the network, and coaches used to run all the way from Scotland to Cornwall with various traction changes en-route.

 

 

 

Classes 81-87 eth didn't rectify to DC, it was supplied as AC.  Don't know about later AC classes. 

 

The original restriction on the WCML Mk2 Pullmans only being able to be heated by an AC locomotive was because the coaches had transformers directly across the train supply.

Edited March 4 by DY444

[45125]

11 hours ago, DY444 said:

 

Classes 81-87 eth didn't rectify to DC, it was supplied as AC.  Don't know about later AC classes. 

 

The original restriction on the WCML Mk2 Pullmans only being able to be heated by an AC locomotive was because the coaches had transformers directly across the train supply.

All the AC classes supplied AC etc, all the mk2s, 3s have rectifiers to convert to DC for aux supplies and the Mk4 has the stat con to do the same.

 

[Davexoc]

12 hours ago, DY444 said:

 

Classes 81-87 eth didn't rectify to DC, it was supplied as AC.  Don't know about later AC classes. 

 

The original restriction on the WCML Mk2 Pullmans only being able to be heated by an AC locomotive was because the coaches had transformers directly across the train supply.

 

I knew there was something odd about the Pullmans.

So supplementary question to the OP, if an ETH diesel dragged an AC loco and its coaches off the juice, could it supply ETH through the AC loco jumpers?

Assuming there were contactors on the AC loco that stopped DC going somewhere it shouldn't....

[45125]

2 hours ago, Davexoc said:

 

I knew there was something odd about the Pullmans.

So supplementary question to the OP, if an ETH diesel dragged an AC loco and its coaches off the juice, could it supply ETH through the AC loco jumpers?

Assuming there were contactors on the AC loco that stopped DC going somewhere it shouldn't....

The simple answer is yes, the diesel will supply ETH with the pan been down on the electric the BIS will also be out so the contractors will not close, if the BIS is in (which it shouldn't be) the voltage detection circuit will prevent the contractors from closing. 

Al Taylor

 

[DY444]

10 hours ago, Davexoc said:

 

I knew there was something odd about the Pullmans.

So supplementary question to the OP, if an ETH diesel dragged an AC loco and its coaches off the juice, could it supply ETH through the AC loco jumpers?

Assuming there were contactors on the AC loco that stopped DC going somewhere it shouldn't....

 

Yes, as long as the coaches weren't the aforementioned WCML Mk2 Pullmans with their as-built electrical system.