Z-4000 and ZW-L together on layout - any problems with chopped vs. pure sine wave?

I have one ZW L and two z 4000 powering the track on my RR and have zero problems and great signal in the command enviroment.

Don,

    Good to know, thanks much.

PCRR/Dave

Common grounds are certainly not a problem.  If you end up paralleling them, you might have an issue if it's for an extended period of time.

John - what is paralleling refer to?

fyi, I would never even thought about an issue except for a magazine article - I think it was OGR George Brown's review 2-3 years ago - where he discussed chopped vs. pure sine waves and how MTH engines run best on pure and Legacy best on chopped. I don't know how serious it was, or if it was even accurate or not, but I thought I'd ask.

Paralleling refers to when the transformer outputs are connected together.  This happens during normal running when you cross power districts, but if connecting them permanently in parallel is a bad idea.  This applies specifically to variable transformers, and transformers of different types.  The only condition you should consider permanent parallel connections is if you have identical fixed transformers and you need more than 10 amps.  Personally, I think this is a bad idea as well, but people do it.

I don't set a lot of stock in the chopped vs. pure waveform arguments with some minor exceptions.  Older MTH PS/1 stuff tends to run better on pure sine wave transformers, and some Lionel locomotives with smoke in conventional mode get better smoke with chopped waveform transformers.  Generally, for command use, I have yet to see a difference.

gunrunnerjohn posted:

...

I don't set a lot of stock in the chopped vs. pure waveform arguments with some minor exceptions.  Older MTH PS/1 stuff tends to run better on pure sine wave transformers, and some Lionel locomotives with smoke in conventional mode get better smoke with chopped waveform transformers.  Generally, for command use, I have yet to see a difference.

I agree, John.  I also recall that the chopped sine wave argument comes into play with better smoke-unit performance for Lionel locomotives operating in conventional mode at slower speeds.  In command mode, voltage to the track is already a steady 16-18volts.  So the chopped vs. pure sine wave advantage levels off considerably.

David

Thanks everyone.  I don't envision needing to hook-up parallel running, so combining Z-4000 and ZW-L should be good for me.

Given that the original ZW's put out a pure sine wave I wonder why Lionel chose to make their newer ZW-L put out a chopped sine wave - anyone know? Does it have to do with taking full advantage of the 200 speed steps with Legacy engines - would a pure sine wave transformer not be able to accomplish the same results?

Paul,

   I am not an Electrical Engineer, however I can tell you I run Legacy with all my Z4K's and the old ZW's and the Legacy Engines have the full 200 step capability using them.  It might have something to due with new ZW-L programmable Channels however, just a WAG however.

PCRR/Dave

Thanks, Dave.

I just found Runs' 263 and 264 - OGR's review of the ZW-L. They're wordy reviews but had some interesting notes. I couldn't tell if the ZW-L hosts banana plugs or not - which is a simple and convenient feature of the Z-4000.

There's nothing about powering with the Z-4000 that would affect the Legacy features.

Paul, the original ZWs, from about 1950 era, used a roller moved by the handle, which would tap off the appropriate number of turns on the transformer secondary to set the voltage.  Apparently the new transformers use electronic circuits to reduce the maximum voltage to the desired voltage.

Paul,

   Sorry buddy the new ZW-L does not have Female Banana Plugs on the front of it, which is a bummer, for a transformer costing that much money.  Which means I would need to retro fit the ZW-L as I have done with the original ZW's.

PCRR/Dave

Good information, thanks again. Its a bummer about lack of banana plugs on the ZW-L - plugs really make wiring hook up easy to Z-4000 and TIUs.

fyi, An article in Run 265 explains why Lionel chose to go with chopped sine wave output ~ it apparently allows more power to control features while running in conventional mode at lower voltages.

FWIW, In Run 264 - George Brown tested a variety of engines powered by the ZW-L - and some older QSI system engines didn't do so well, but all modern command engines did fine.

Truthfully, I think Lionel went with the chopped waveform simply because it's easier to control voltage vs. synthesizing a sine wave.  The fact that it aided conventional operation with smoke was just a happy coincidence. The circuitry that MTH uses to generate their variable voltage sine wave is more complex than other electronicly6 controlled transformers.  I used to have to generate 400hz sine waves for synchro controls for avionics, it's a lot more complex than handling a couple of triacs.

John, your probably right-on, I recall George Brown cited cost as another reason.

I had no idea about the complexities of transformer wave outputs.

Hi guys,

Have to work on a photo, sorry!  I'm with a modular railroad group and wanted to chime in on the subject.  We have a ZW-L on our layout and it does not appear to be compatible with parallel running with some other transformers.  When it runs in parallel with a postwar ZW or MTH Z4000 it will short out.  I suspect this is due to the chopped sine wave output by the ZW-L and the pure sine wave output of the postwar ZW and Z-4000.  Can anyone confirm this?  This happens even when removed from the layout and wired together just to eliminate any layout issues.  To confirm, I wired it in parallel with Z-750 with a controller attached (which I believes chops the sine wave) , and they work together just fine (no short) but, however,  connecting to postwar ZW or Z4000 produces the same short as when on the layout.  I tested it against two postwar ZW's and two MTH Z4000's  and all 4 transformers shorted out when parallel with the ZW-L.  Has anyone else experienced the same?  This is a bit of a problem for us since there is only one ZW-L on our layout and we cannot run it in parallel with any of the other 5 transformers on our layout.  Hate to lose the great features of the transformer, but it looks like it's easier to swap out one than the other 5 to maintain compatibility.  Any thoughts?...anyone else experience the same?

Thank you and regards to all!

Mike

Since there has been confusion on definition, please describe exactly what YOU mean by parallelling.

When both transformers are powering the same section of track. 

That is not a good idea, ever.  If both are not precisely at the same voltage all along their waves, there are current flows between them.  Z4000's are said to shut down if they are paralled with each other.

I'm staying out of this one!

My one comment to this thread, IMO this is a terrifically bad idea!  Paralleling any variable voltage transformer is bad, and dissimilar ones are worse. The only type I'd consider it with is identical fixed transformers.

Truthfully, I see no reason to parallel transformers in any case.  We did that for one show for our modular club, and derailments were spectacular, to say the least!  No thanks!