WTIU on Multiple Transformers

ANYTIME you use more than one transformer on any layout- you should ensure they are in phase.

Why? Because failing to do so likely creates a condition where the transformers ADD voltage- meaning there is a point with **** near 36-40 Volts on the layout between 2 wiring points.

Part2- let's get this right too- the problems to date with the WTIU have been ELECTRONIC controlled transformers putting out a distorted waveform. A classic ZW is pure sine wave, and thus not an issue in that regard.

@Vernon Barry posted:

ANYTIME you use more than one transformer on any layout- you should ensure they are in phase.

Why? Because failing to do so likely creates a condition where the transformers ADD voltage- meaning there is a point with **** near 36-40 Volts on the layout between 2 wiring points.

Part2- let's get this right too- the problems to date with the WTIU have been ELECTRONIC controlled transformers putting out a distorted waveform. A classic ZW is pure sine wave, and thus not an issue in that regard.

The track loops are completely independent of each other, does the WTIU, albeit thru separate inputs, somehow combine the two transformers to a point where the phasing is required? (Ex.  ZW 1 to WTIU Fixed 1 to Loop 1, ZW 2 to WTIU Fixed 2 to Loop 3)

Thank you for your clarification on the ZW and sine waves.  New to the entire DCS/TMCC world and learning as I go along.

@Rob Schreiber posted:

The track loops are completely independent of each other, does the WTIU, albeit thru separate inputs, somehow combine the two transformers to a point where the phasing is required? (Ex.  ZW 1 to WTIU Fixed 1 to Loop 1, ZW 2 to WTIU Fixed 2 to Loop 3)

Thank you for your clarification on the ZW and sine waves.  New to the entire DCS/TMCC world and learning as I go along.

Even IF they are independent loops, internally it's one box (the WTIU) so if the transformers are out of phase, you have that 36-40V potential between channels.

Again, as I said, even if you think you are isolated- the risk of running 2 transformers out of phase and sending a peak voltage of 36-40V into component rated for no more than about 22V is a sure fire way to have a bad day.

Phase your transformers or only use a single multiple output transformer- such that it is near impossible to get out of phase and that killer 36-40V condition.

And yes, in one the WTIU topics recently, a person had issues because they didn't phase the incoming transformers and yes it caused an issue.

Also, the instant you begin using TMCC/legacy- that requires the base to be common to all outside rail- so your power and track system becomes common- even independent loops- all the more reason to ensure you are "phased".

If I was doing this- using a ZW and a WTIU- I would wire it to use one ZW, all 4 channels, the 2 inner handles set to 18V constant and feed to the 2 variable channels of the WTIU, and the 2 handle channels of the ZW to the fixed channels. I would put a fast acting breaker or fuse between each of the hot leg output posts between the ZW and the red input post of each TIU channel- probably a 5 to7.5A breaker for most of my use cases. I would ensure all U posts were connected to the black input posts of the WTIU channels and ensure they all were bonded together (a known failure on some ZWs with bad U post connections).

This gives you options- like using the variable channels as variable- meaning remote control variable to run a conventional train using the DCS app.

Thank you Vernon.