ZW-L and Z4000 oscilloscope traces

Thank you!  This is great.  Four of five years ago I took the Z4K to our lab and measured it and saw the slight "notchiness" around the zero crossing (the waveform departs on there from a real 60 cycle sine wave - it seems to hestiate and then plunge vertically across, etc.).  These do show why the ZW-L runs my conventional locos better though.

Again, thank, this is superb!

Ingeniero. thanks for posting the scope pictures. They really show the differerence between the Z4K and the ZW-L. I always suspected the Z4K waveform was not a perfect sine wave, but it's a lot closer than the ZW-L.

Very good! Thanks for doing this. I wonder how MTH maintains a sine wave because I'm sure the voltage is electronically regulated.

Cjack, if you are really curious, and have an hour or 2 to spend, read the Z4k patent: #6,281,606.

Great Alex, thanks for the pictures.

Thanks. I did/will look at it. It is clearly a pulse width modulated regulated supply. I'm not sure how it works in detail and I guess it doesn't really matter other than it looks cleverly done.

So in summary of my reading:

The ZW-L and Z4K at around 18v are very similar.  At lower voltages the Z-4000 maintains a closer sine wave, while the ZW-L clearly shows the pulsed power.  Both still runs trains very nicely, but newer trains may work better on a ZW-L at lower conventional voltages.

Thanks for taking the time to do the research and share.  Awesome post!

Jim

Hi Alex, cool stuff. Thank You.

Here's the Lionel video guy in "Chop vs. Smooth Sine Wave".

Not being an EE, I gather these conclusions:

1. Your smoke units and couplers work better when using chop when in conventional mode.(Lionel products)
2. If you put either wave type through a TPC or a PM it comes out chop.

Is that the same for the TIU?

@Ingenerio No1-Did you test at the TIU or transformer?

Chopped or smooth may be good for some things, but if my train runs ok, I'm good.

Everyone - Thanks! Very glad to do it - as long as you find it helpful.

Moonman,

For the first set of tests I measured the voltages and connected the scope to the track - after the TIU's. Then I repeated the same tests at the transformer posts while they were connected to the TIU's and these were powered. There was no difference in the voltage levels or the traces. The traces I posted above (the last two, with the 'noisy' traces, were at the transformer posts.

The traces I obtained today were with the transformers not connected to anything.

Here is a bit more explanation on the scope traces for those interested.

The Z4K at 15V is close to a sine wave, so its peak value is the 15V times the Square Root of 2 (1.414) = 21.2V. The ZW-L is not a perfect sine wave at this voltage level.

Thanks for looking.

Alex

Thanks, Ingenerio.

That helps me understand what the equipment is doing. Sorry I missed your earlier posts.

I appreciate your time and sharing the information.

Edit: I read your post with the first round of testing.

So, it would seem to me, that they are equal for DCS or Command operation. If you are running Conventionally, match the transformer and product manufacturer.

This is very helpful, Ingeniero No1.  It helps me understand how and why the ZW-L does so much better on controlling locos conventionally.

As to testing under load, for what is is worth, two data points.  Several weeks ago, John Zahornacky commented to a thread on the "voltage accuracy" of the ZW-L that that the throttle control ring is calibrated 0 to 20 at full throttle for hisotrical and legacy (small L) reasons, but that it was built to put out a maximum of around 18 volts RMS, so 20 = 18 volts RMS or thereabouts.  He said this would drop a bit - I recall the impress this meant 1/2 to 1 volt, no more, under load. 

    I measured voltage-drop-under-full load with a train that requires a full ten amps to run nicely (this is the Lionel Santa Fe Anniversary passenger set locos - ABBA set with four Pullmore motors, and in this case eight incadescent lighted cars).  At throttle setting 18 on the ZW-L the current flow starts the red light on the left side of the ZW-L blinking as the unit's voltage intervention kicks in (the second level of protection as described on the first two pages of the owner's manual).  At a throttle setting just below 18 - about 17.5 - the light is not blinking, the ZW-L's current meter says exactly 10 amps, while the unit's the voltage meter says 14.5 volts -- and a multimeter at the transformer terminals says 14.7.   At this exact setting with the no load the current meter of course says no current and the ZW-L's voltage meter says 15.5-16 volts RMS (can't read it any closer) and my multimeter says 15.8. 

Moonman, Lee –

Since I run only DCS and Legacy, I just move the handles of the ZW-L to the maximum since at this setting the voltage is around 19V and safe for the trains, as far as I know. (But I may be wrong )

On the other hand, I watch the Z4K voltmeters closely as depending on the load, the output could vary up to 22V or higher. Note that the actual Z4K voltage output can be 0.9V over the meter reading, so when the Z4K meter reads 18V, for instance, the actual voltage could be 18.0V to 18.9V. Very good meter indications, I would say.

During my testing I found that the meters on the Z4K’s closely matched the multimeter regardless of voltage level since the Z4K output is very close to a sine wave throughout. With the ZW-L, and was noted above, the output closely matches a sine wave only at the higher voltage levels, and some multimeters will not read correctly at the lower voltage levels.

Thx!

Alex

Alex,

   Thanks for the education, I appreciate it.

PCRR/Dave

Dave,

Thank you for reading it! I enjoy all of this stuff as well.

One point I wanted to reiterate is that I tried five different multimeters, and of these, three read the same or very close as the ZWL & Z4K voltmeters, but one read higher, and the other lower; and these differences varied according to the transformer voltage settings. The multimeters that read the same, or close, reflect the areas under the voltage curves, which are about the same for the Z4K’s and ZWL’s regardless of the peak voltage.

Thx!

Alex

Most voltmeters are calibrated for a sine wave. Anything else is likely to get an inaccurate reading.

   i watched the  Lionel sine / stepped video.  The smoke is a heating element. The heat is determined by the power no matter how you get that power. Also no mentioned is the fact that the stepped output, If not properly designed, can produce radio frequency interference. Don

From experience I can tell you Z4000s are not regulated. As the current draw increases from zero to 10 amps the voltage will drop. Also they are not regulated for input voltage either or if they are its over a very small range like 115-120 volts. Below 105 volts input it stops working. Not an issue for most here but our modular club sets up at a few venues (like local fairs) where power is a bit dodgey. Thats why we keep the trusty Post War ZWs on hand.

Pete

Well they are regulated, question is, how well? In addition to the droop of the internal connections and loose regulation, there are also voltage drops which contribute to the lowered voltage. For example, a 0.1 ohm resistance at an out put connector can contribute a 1 volt drop when going from 0 to 10 amps. In order to combat that, many high current power supplies bring out voltage sense leads to measure the voltage at the distant load rather than inside the power supply device.

I'm familiar with regulated power supplies. I have a number of them in my lab but by definition regulated means one of the components (voltage or current) remains within a small value of deviation over the rated range. I am going by the meters on the transformer itself. At zero current the voltmeter may read 22 volts with the handle at max rotation. At ten amps the voltmeter drops to 18 volts. In this case the meter readings have nothing to do with resistance outside the transformer.

I am open to "peer review". Anyone can try this experiment for themselves.

Pete

Norton:

Looking at those scope traces, You are correct. The Z4K is a chopped sine output. It is just chopped very fast and resembles a sine output in rough view.

Pete, Russell -

I agree. And as far as the regulation goes, not all four channels of my two Z4K's exhibit the same degree of regulation, or lack of. One of the outputs remains between 19V-21V with currents from about 1A to 6A. But another output will vary 21V to 17V under similar load conditions.  The ZW-L appears to be better regulated.

Alex

The next phase of this should be a discussion of the theory of how this applies to PWM motor control and the different principles.  My understanding is the pulsing at high voltage has its advantages with initial torque for the motor.

Of course MTH and Lionel use two different approaches.  MTH converts this AC to DC at the fronted of the board and has the High DC Positive Voltage available at the motor, lights, coupler, smoke heater etc.., and regulates the return to DC ground to control the effective voltage down to 6V for lights, 12V? for motors.  I believe Lionel at least for TMCC stuff had the Ground available and pulsed the AC wave form going in to the motor, and for DC motor engine, convert the AC at the Motor Driver and still pulsed the positive DC.

So does the circuit design and algorithim for PWM determines which AC wave form is best for the as designed engine?   G

So when we pass this information on,

The new Lionel transformer is giving a very high spurt of voltage to the equipment and cutting it short to resemble lower voltage?

The Z4000 is much more like a post war ZW with a wave?

Thanks