Electric Loco controls

[Kentish Paul]

Having seen various bits on the above. Can someone explain how it works. Class 76 (out of date I know) seems to have major handels for different controls. Class 81-87 has controls such as notch up / run up / hold / run back /notch back etc. Can someome explain how this works.

Simple west country person (now living in Kent) used to steam and the other. Thanks in advanced.

 

[Harbon 1]

Basically for 81-87 the driver had to 'notch up' the power, and be careful not to overload the transformers. Then 87101 was experimentally fitted with a thryster controller, which is I suppose the same as a diesel, not having to worry about the amps I think. That's how they're all controlled now

 

[LE Greys]

Didn't you used to have to go back to Notch 0 then up through every single notch if you wanted to reduce power, or something like that?

 

[Harbon 1]

You couldn't just shut the notches off, or youd have to wait for the 'taps' to run down, then reset the system before applying power again

 

[ainsworth74]

Wasn't that slammers rather 81-87?

 

[O L Leigh]

No. Slamdoor AC EMUs and AC locos had the same system of mechanical power control. These could be referred to as tap-changers or camshafts.

If I'm understanding it correctly, the main transformer had a number of "taps" put into the transformer secondary winding at various points. The amount of power transmitted to the motors would depend on which "tap" was selected. The power controller was not the same as in modern traction in that the higher the notch you select the more power you apply, but it controlled the position of the tap-changer/camshaft within the transformer either up or down.

O L Leigh

 

[dubscottie]

Having seen various bits on the above. Can someone explain how it works. Class 76 (out of date I know) seems to have major handels for different controls. Class 81-87 has controls such as notch up / run up / hold / run back /notch back etc. Can someome explain how this works.

Simple west country person (now living in Kent) used to steam and the other. Thanks in advanced.

Ill scan a VERY old mag with a good description of the 76/77. I would think any copyright would have expired by now! (published 195x by a now defunct company)

 

[junglejames]

Having seen various bits on the above. Can someone explain how it works. Class 76 (out of date I know) seems to have major handels for different controls. Class 81-87 has controls such as notch up / run up / hold / run back /notch back etc. Can someome explain how this works.

Simple west country person (now living in Kent) used to steam and the other. Thanks in advanced.

As mentioned, 81s to 87s had Tap Changers. 87101 and onwards have Thyristor controls. Tapchangers, you notch up, keeping a keen eye on the ammeters. As soon as the current approaches the red, you take the power controller back to 'hold', then wait for the current to reduce, before notching up a bit more.
The only position you are missing is the off position. Im pretty sure ive seen the controller taken straight to the off position when approaching neutral sections. So the same would apply for slowing down as well. Especially for stations.

Moving onto the 89, 90s and 91s and 92s, they are thyristor controlled, like 87101. The power can be applied seamlessly (for want of a better word). There are no notches.
However the power controller actually acts more like an acceleration controller (if that makes sense). The speedo has a speed selector knob on it. Select the speed you want, then open the power controller. The more you open the controller, the faster the acceleration. You dont actually control the speed itself with the controller. You can use the power controller as a conventional controller, but you apparently have to isolate the speed selector first. In everyday operation, this is rarely done.

When accelerating, the computer controls the current. So you dont need to worry about applying too many amps. So if your light engine, set the selector to whatever speed you want, open the power handle fully, and overtake absolutely everything in sight!!

The speed selector could also slow the train down as well, however it will only apply the locomotive brakes, and not the train brakes, therefore it is never actually used for this. Youd have to bring the controller back to 'off' than apply the train brakes conventionally until you reached the required speed, then reduce the speed setting on the selector, before opening the controller again.

As for a class 76. I have no idea!!!

 

[trainplan1]

As mentioned, 81s to 87s had Tap Changers. 87101 and onwards have Thyristor controls. Tapchangers, you notch up, keeping a keen eye on the ammeters. As soon as the current approaches the red, you take the power controller back to 'hold', then wait for the current to reduce, before notching up a bit more.
The only position you are missing is the off position. Im pretty sure ive seen the controller taken straight to the off position when approaching neutral sections. So the same would apply for slowing down as well. Especially for stations.

Please correct me if I'm talking out my backside but is the order OFF, RUN DOWN, NOTCH DOWN, HOLD, NOTCH UP, RUN UP for the sequence? Or for one of the classes at least?

For isolation sections I assume the driver would move it to off sometime before the section (enough time for it to run down to 0) then straight back up once cleared?

So if your light engine, set the selector to whatever speed you want, open the power handle fully, and overtake absolutely everything in sight!!

I have seen a class 90 depart light loco, shame it wasn't on 4 track alongside an EMU

 

[wilsontown]

I'm no expert, but I believe trainplan1's order is correct. The handle will normally be in "HOLD", and will be moved to "NOTCH UP" or NOTCH DOWN" to increase/decrease power by a notch. "RUN DOWN" would be used to decrease power rapidly, perhaps before a neutral section, while "RUN UP" could be used to rapidly restore power after it had been taken off while running at speed.

Do feel free to point out which bits of that are wrong though...

 

[junglejames]

Please correct me if I'm talking out my backside but is the order OFF, RUN DOWN, NOTCH DOWN, HOLD, NOTCH UP, RUN UP for the sequence? Or for one of the classes at least?

For isolation sections I assume the driver would move it to off sometime before the section (enough time for it to run down to 0) then straight back up once cleared?

Yep, thats the order

I have seen a class 90 depart light loco, shame it wasn't on 4 track alongside an EMU

Apparently an 87 is actually even quicker. Reason being, you can take the ammeters on an 87 up into the yellow, and keep them there. On a 90, the computer doesnt allow that.

 

[captainbigun]

Broadly speaking the descriptions above are right. On 81-87 the controller has Off, run down, notch down, hold, notch up, run up. The controller has to be held in run up.

81/83/85 have low tension tapchangers. The transformer is tapped on the secondary side, that feeds a rather large tap changer assembly which gives 38 notches plus 2 weak field stages on the 81/5.

82/84/86 and 87/0 all have high tension tap changers with a tapped primary. The transformer in the 82 is all but the same as that eventually used in 86. All have 38 notches. 86/1 and 87 have a single weak field stage. The tap changer is in oil with only the diverts out of the tank for ease of maintenance.

81-87 all drive broadly the same, you notch up or down to move the tap changer a single notch. Safe driving keeps the ammeters in the green, but you can safely go to the top of the yellow to press on!

For neutral sections the driver will aim to have run down to notch 0 just as they enter the neutral. Breaker opens, closes and then straight in to run up to get the amps up as quickly as possible. The tap changer must be back at zero before the breaker will re-close. If you enter the neutral on load not only will it jerk the train due to the sudden loss of power but it will wear the contacts on the breaker more quickly. It's bad driving.

87/1 introduced thyristors for the first time. Effectively this gave a controllable rectifier with infinite steps between zero and full power. It was generally driven like any other 87 with the control electronics mimicking an 87/0. However it had an advanced mode which allowed the power handle to perform the same function as the controller in 89/90/91 with zero to max TE. Theoretically you'd throw it into max and let the loco's electronics take car of the rest.

Same applies to thyristor locos in neutral sections, shut off just as you enter then crack the controller open as the breaker closes.

89/90/91 added the speed set function as above.

The early tap changer units up to 313s all had an arrangement similar to 81/85 with low tension tap changing but far fewer taps.

 

[Kali]

76s have manual field diverts, that will explain one extra lever. There's a seperate regenerative brake lever also, some of the AC units had a seperate lever for that too.

 

[trainplan1]

Yep, thats the order

Cool, thanks for clearing that up

Apparently an 87 is actually even quicker. Reason being, you can take the ammeters on an 87 up into the yellow, and keep them there. On a 90, the computer doesnt allow that.

Blimey, well I was pretty impressed with the 90's getaway so I'd love to see an light loco 87 really go for it.

 

[starrymarkb]

OBB Taurus 0-120km/h in 15 seconds.

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