Series wiring for DC can motors

I can't say if you can wire the motors in series when using ERR cruise commander.

 

However you can wire motors in series to slow them down. I have never found the need to wire any engine's motors in series, even with my Williams I keep them in parallel.

I use a smaller transformer or DCS and track voltage setting to run my Williams better.

 

I could wire the motors in series as that is not hard for me to do. I work with 240 volt circuits at times so low voltage series is nothing.

 

Lee Fritz

I recommend you do not do that.  There is really no upside, and the Cruise Commander was designed to run the motors in parallel.  Perhaps Jon Z. from Lionel will check in, he designed that board, but I suspect he'll tell you the same thing.

 

 

I suspect your right John.
Someone suggested I wire it in series. I thought I would ask before I do that. This is my first TMCC upgrade and I'm not sure what kind of proformance to expect from it.

I tried it once with a set of K-Line Interurban cars, in series they could barely get out of their way.  That cinched it for me.

 

It really should not be a problem.  Putting the motors in series doubles the resistance, cuts the voltage to each motor in half, cuts the current in half and cuts the power to 25%.  If one end starts to slip, the other motor looses all its torque.

I have most of my two motor locos wired in series.

 

It does give me smoother performance and better low speeds.   As mentioned above, the voltage to each motor is cut in half.

 

I use DCC and it does care whether they are in parallel or series.   It only cares about how much current it might draw in a stall.    as long as the stall current stays below the decoder rating, all is well.

You're only telling half the story.  Yes, series wiring will only deliver half the voltage to each motor.  However, in order to develop the same motive power, you'll have to raise the total voltage applied to the series string to twice what you'd have for the parallel motors.  You end up needing the same amount of motive power to do the same amount of work, there is no free lunch.

 

The major benefit of series wiring motors is for low speed conventional operation, that's why it's popular with many folks that run Williams conventional locomotives. They tend to start with a bang with most transformers starting out at around 5 volts, so the series wiring fills a useful role.

 

For a back-EMF cruise control, I see no utility in series wiring, and it will significantly limit your pulling power.  Low speed control is not an issue with the ERR Cruise Commander, so the only perceived benefit doesn't exist.  You will NOT draw more current wired in parallel for the same speed and load as wired in series using the Cruise Commander.  Since there is only a finite amount of voltage available from the output of the Cruise Commander, the series wiring will significantly limit your pulling power and top end.  Most folks may not notice the lack of top end speed, but more will surely notice the lack of pulling power.

 

I use series diodes. Does not reduce pulling power and there is no uneven distribution of voltage to the motors on curves as with series wiring. Here is the method I use. 

 

link

 

Just to add I have put these on some cruise locomotives. It alleviated "Odyssey Lurch" in 2 Lionel locos I had. Not sure how it would work with ERR in command specifically.

 

Dale H

Actually, anything that reduces the maximum voltage to the motors would by definition reduce pulling power.  The real question would be how much it reduces it, and if it's an issue in actual operation.  The ERR back-EMF may suffer from the series diodes, I've never tried that.  They are measuring the back-EMF, and that would logically be affected by the diode drops.

 

Maybe not if the drop is before the rectifier, at the input.  No different then turning down a transformer.  Your basically using diodes to compensate for a transformer that can't lower voltage enough for the reverse unit.   While I agree, not needed for a cruise engine like ERR.   G

George, you just move the voltage range lower.  If the transformer goes from 5 to 18 volts, and you stick enough diodes in to accomplish a 3V drop, you'll be going from 2 to 15 volts.  You still don't have the same top voltage, although as I said, in most cases that probably isn't a major issue.

 

My real point was for cruise control, it's not needed or desired.

 

There is another benefit to wiring motors in series. If you are running in conventional mode, with no command system, the loco wired in series is less sensitive to slowing down on various areas of the layout where the voltage sags.

I don't see how that can really be.  If the voltage sags, you're going to lose speed in any case.

 

Right, it reduces top end, but I was referring to Back emf process.  Should be no effect on it since it is a lower input voltage.   G

I disagree, I think it would have an effect on the back-EMF sensing.  You're having a voltage drop going out, and you're also having one coming back.

The voltage sag is generally related to the current being drawn across whatever high resistance connections are in the track or the wiring. This is assuming that what ever is causing the voltage to sag is resistive in nature. The less current being drawn, the less the voltage sag. On top of that, the total track voltage is higher with series wired motors, so the voltage sag is a smaller percentage of total voltage.

 

If you will allow some math with the numbers made up for ease of calculation. This is a hypothetical example.

 

Two parallel wired motors, running at 6 volts pulling 2 amps will make a certain track section sag 1/2 volt. 1/2 volt sag of 6 volts is roughly 8%.

 

The same two motors wired in series running at the same speed on the same section of track will be at 12 volts pulling 1 amp. Since the current drawn is 1/2 of what it was with parallel motors, the voltage on that stretch of track will only sag 1/4 volt. 1/4 volt sag of 12 volts is roughly 2%

 

2% is less than 8%, which confirms my earlier statement that series wired motors running in conventional mode will be less sensitive to sagging voltages on different parts of the layout.

 

Lighted passenger cars will tilt the equation, but a freight train should behave as I stated.

Motors in series do not always share the load evenly even if they are identical. To witness this yourself, turn an engine upside down and run it. If the motors are in parallel,stopping one truck with your thumb will not affect the other truck speed very much. If the motors are in series,stalling one truck will result in the other truck speeding up. On a sharp curve approach this could happen during operation. Can pull of traction tires with one truck dragging the other.

 

A PWZW puts out 20 volts. 2 motors in series would be limited to 10 volts. Cruise control locos would allow even less.  2 motors in parallel would get 20 volts minus the diode drop. If 4 diodes are used in series that is about 17.5 volts without cruise. Most people in conventional don't run the motors even that high so there is no effective loss of pulling power. In effect you are limiting the top throttle just a bit. If cruise equipped with voltage held in reserve it might be a slight issue,but much less so than series wiring IMO.

 

Dale H

Roy, instead of a kludge like serial wiring, I'd fix that poor trackwork.

 

Not if it is at the input to the rectifier.  The board then gets lower voltage to start and reference from that input.  No  different then setting a transformer at 10V in conventional.  I am not talking about motor diodes.  Which is why I stated in front of rectifier when I posted.  I don't think that would effect the back emf reference.  G

Come on down to the mall and give us a hand with that.

OK George, I agree with that.  If you're just limiting the voltage at the track feed, the back-EMF won't be affected, that's true.  I missed that detail.

 

Roy, you can't afford my travel costs to come and fix your track.