MTH Z4000 SMOOTH SINEWAVE ?

"the sky is falling"

All the "Lionel type locomotives" on our layout (3rd Rail, Lionel, Weaver, Atlas) all work just fine with the Z4000s.

This goes back years. Basically, there are two ways you can adjust the voltage in an AC context:

1. A variable step-down transformer that uses a wiper to change the number of windings through which the source voltage runs, thus changing the output. This is how the original Lionel transformers worked (worked well and still do.) BTW, a sine wave is NOT square; it is very smooth and curved. For home-made, you could use a 120-volt to 24-volt step-down fed from a 0-120V "autotransformer" (Variac is a brand name that comes to mind.)
2. "Phase-limiter" electronics, which chop out part of the sine wave. This is problematic as the electronics in the engine pick up the "blips" when they expect a small sine wave. You can run something simple like an AC drill with something like this, but not something with more sophisticated electronics. This drives QSI-based sound/reverse units NUTS! As a practical matter, it's not that great for the electronics either because of the pulsing. Two of the worst offenders were the Lionel RS1 transformer and the original MRC Dual-Power O-27. The original Lionel Powermasters were pretty bad, but could be cleaned up somewhat using 100uF to 200uF NON-POLARIZED electrolytic capacitors to smooth out the output sine wave.

DC throttles are simpler because they use electrolytic capacitors to balance the output after the input AC has been rectified and stepped down, so you don't hear of as many issues.

 

Based on what the innards of a Z-4000 tranformer look like, I believe MTH uses a hybrid approach. If you use a clean DC-output throttle, then run it through a high-quality inverter (very close to pure sine wave output,) you get clean variable AC. There have been several high-quality inverters on the market for decades in the form of uninterruptable power supplies, RV power systems, and all of those solar power kits out there. Some use a step-up transformer to go from 12-24 volts DC to 120-240 volts AC. Without the step-up transformer, you'd get AC that's somewhat close to the source DC voltage -- i.e., 0-22V. MTH adds a microprocessor control to the mix -- probably to monitor everything and make fine internal adjustments. Feeding a good inverter with a clean DC power source is less expensive and mechanically more reliable than rollers on a custom-wound variable transformer. Should the variable resistors wear out, they're readily replaceable. We've been using Z4000's at the club for years and they've worked reliably.

After read a topic from a OGR member (AGHRMatt)29 septembre 2012 

 

Question concerning MTHZ4000

Under big load:

If there is an automatically dynamic load balancing in the MTH Z4000 to keep the maximum outpout at 10 amps-18 volts =180 watts. 

John

Que?

OK, I don't want to come off harsh but;

The Definition of SINE wave is a rounded wave whose characteristics can be calculated using the sine math function. Quite the opposite of a Square wave.

And not even the Chopped wave transformers such as the CW80 and the Z-1000 output anything like a square wave.

They output a portion of the sine wave, and I can't profess to have put an o-scope on my transformer but most controls of this type chop on at a determined point in the sine wave and then turn off when the wave passes thru zero volts prior to going to opposite polarity. This is by far the least expensive method to control AC power.

 

Now, Engines performing better on chopped sine wave output is probably because a portion of the time the voltage is significantly higher than the RMS average voltage which is what you are reading with a good meter and possibly with the meters built into your transformer. This spike to higher VAC gives the motors a good boost of power even when running slow so they will start moving at lower voltages.

In the case of a can motor it will charge the conversion circuit to DC (Can motors run on DC) faster so the same can be expected.

 

And yes, some older electronics (PS1, ect) did not have the filtering required to run on this switching power supplies. Modern PS2 and Lionel engines have no trouble with it and can use the peaks in the voltage to get the motor moving at lower average voltage.

As to whether the Z-4000 performs as well as a chopped sine wave unit on Lionel engines I have no data one way or the other. I have no access to a Z-4000.

I have one Lionel engine that has tmcc and I use it with my z4000 in command mode with absolutely no problems at all.

I had a Z4000 for about thee years. 

 

I run only conventionally.

 

Everything I had ran well with the Z4K and I really liked it.  Not sure if it was pure sine wave or what - there have been lots of threads about that so you  look them up if you care.  but everything ran well with it.  I was very satisfied.

 

I got a ZW-L when they first came out..  All my Lionel, but particularly Legacy locos, runs much better - smoother at even slower speeds (even in conventional I can run below 10 mph), more linear control, etc.  MTH locos run as well, WBB and Atlas and RMT also as well.  the difference is noticeable but not critical; life with a Z4K is good.  but a ZW-L is better if you have a lot of recent Lionel.

I

I run both Mth ps2 and Lionel Legacy locomotives on a layout feed by a Z4000 without any problem. Few month ago i have to open a Z4000 and revert the plus+ and minus - wire from the power cord because of a wrong polarisation in between two transfos. I exam the internal circuit and  just trying to figure out how the circuit work

John