Transformer Voltage Drop When Accessories Operate

[JTrains]

As I’ve slowly built out our basement floor layout and added accessories, I noticed that trains were starting to drag around curves when certain accessories operate – such as a #151 semaphore and #152 crossing gate.  A voltmeter on my track power binding posts confirmed that when they activated I experienced a drop of about half a Volt to the track, which is enough to make a difference in certain parts of the layout.  Now, both of those accessories have solenoids so I understand they’ll probably draw a bit more current than, say, a #154 which only has lights.  But I have a Type V transformer and it’s certainly not being pushed to its 150W limit.  I have the track and accessories controlled separately on the transformer.

 

I don’t remember this happening when I was a kid, but that was a long time ago.  So my question is: is this behavior normal/to be expected?

 

I haven’t done a rebuild on the transformer (everything works fine, perhaps except this) and wouldn’t unless perhaps that’s the solution to this problem.  The rollers could use replacing and the secondary winding a bit of cleaning – but, again, no sense it fixing something that isn’t otherwise broke.

[ADCX Rob]

Using your voltmeter connected to a lockon on the track at the point the train slows will be even more revealing - a several volt drop. You need heavier wiring to the track.

The Type V is rated at 150 watts input, about 110 watts output.

[sir james I]

Add some more power drops, esp. at the farthest points from the transformer.

[pullman jct]

I see the same behavior. My 455 oil derrick causes the lights to dim in other accessories, even those that are on a different circuit in the same transformer. It is a good idea to use separate transformers for trains and accessories if possible. I use a second transformer to power switches and accessories. 

[lionelsoni]

I have pointed out before that using the track's outside rails as an accessory return, while powering the accessories out-of-phase with the track, will cause the return currents, and therefore some of the voltage drop, to cancel.  Other measures may still be needed, but this may help.

[Pi the train guy]

I've seen this happen before. In your old house the main circuitry is different than your present one, for example, you know how when you turn on your carpet cleaner It will do the same thing. I have a big house, but the same problem. either your circuit board, (in the garage usually), is elderly, or it's just a natural reaction. try to see how dim the lights are, if really noticeably dim try to see what section of the house is dimmed, the circuit board is connected to different sections of your house, and you can pin point the problem!!!

PS. This is an hypothesis, just a possible answer.

[JTrains]

ADCX Rob

Using your voltmeter connected to a lockon on the track at the point the train slows will be even more revealing - a several volt drop. You need heavier wiring to the track.

While it's true that I get about 1V drop between the transformer and my farthest LockOn (which is wired with stranded 16 AWG, about 25 feet) it's the 0.5V drop when solonoid accessories are actuated that I'm curious about.  The same drop occurs everywhere on the track I tested and occurs regardless of the distance between where I'm testing and the accessory.  Perhaps this is just "performs as design" behavior for these type of transformers and the solution would be to place accessories on a different transformer from the track power.

[JTrains]

sir james I

Add some more power drops, esp. at the farthest points from the transformer.

Already got seven! 

[JTrains]

lionelsoni

I have pointed out before that using the track's outside rails as an accessory return, while powering the accessories out-of-phase with the track, will cause the return currents, and therefore some of the voltage drop, to cancel.  Other measures may still be needed, but this may help.

All my accessories get their common ground return via a Lockon - less wiring for the boy to trip over.  But what do you mean by putting them "out of phase"?

[JTrains]

pullman jct

I see the same behavior. My 455 oil derrick causes the lights to dim in other accessories, even those that are on a different circuit in the same transformer. It is a good idea to use separate transformers for trains and accessories if possible. I use a second transformer to power switches and accessories. 

Makes sense - those derricks are another solinoid-containing accessory.  A second transformer is in the plans in the coming weeks so probably this will take care of itself.

[ADCX Rob]

JTrains

 

 

ADCX Rob

Using your voltmeter connected to a lockon on the track at the point the train slows will be even more revealing - a several volt drop. You need heavier wiring to the track.

 

 

 

While it's true that I get about 1V drop between the transformer and my farthest LockOn (which is wired with stranded 16 AWG, about 25 feet) it's the 0.5V drop when solonoid accessories are actuated that I'm curious about...

That's the wrong measurement - it may indicate only half of the voltage drop, and it doesn't reflect the total drop at the track when your accessory activates. You need to check the voltage at both locations - the transformer and at the track where the train slows - under the same circumstances with the total load.

The transformer, yes, is only seeing the .5 volts, but what is the drop at the track location?

[JTrains]

ADCX Rob

 

 

JTrains

 

 

ADCX Rob

Using your voltmeter connected to a lockon on the track at the point the train slows will be even more revealing - a several volt drop. You need heavier wiring to the track.

 

 

 

While it's true that I get about 1V drop between the transformer and my farthest LockOn (which is wired with stranded 16 AWG, about 25 feet) it's the 0.5V drop when solonoid accessories are actuated that I'm curious about...

 

The transformer, yes, is only seeing the .5 volts, but what is the drop at the track location?

Hehe...probably should have been a bit clearer.  I'm seeing voltage drop 0.5V at both the transformer and the distant LockOn whenever the accessories actuate, which then increases back when the accessory is no longer actuated.  That said...

...I always see ~1V lower voltage at this LockOn compared to the V's binding posts under the same running circumstances (i.e., when the V reads 11V, the track is reading about 10V on the same analog voltmeter).  I do regain a bit of that with the LockOns closer to the transformer and have thus chalked it up to the wire - although I would have thought that's a bit much of a difference for only 20 or so feet of 18 AWG only drawing 2-3 amps.