Legacy and KW transformer

DBHONE,

   You will also need TVS protection for your set up.  Do and OGR search for the way to add TVS protection, there are several threads explaining how it's done.  Further if you run DCS also, the TIU has built in TVS protection.

PCRR/Dave

dbhone posted:

I am converting to Legacy/TMCC and confused about circuit breaker protection for my Legacy and TMCC locos.  I have an in-line fuse between the track and transformer and can use either 7 1/2 or 10 amp fuse.  Is this sufficient or do I need the little Lionel track side shed breaker for additional protection? Or something else?

If you use the Lionel Powerhouse(s), the breaker in them is extremely fast and as well is the new ZW-L. What are you using for power? If it is the older prewar ZW, you need better, faster protection. Such as the PXS-AC   http://amhobby.com/products/te...owershield_x_ac.html  This is probably the absolute best protection.

Charles RO among other dealers has this...

http://www.charlesro.com/store...p;Category_Code=OLTP

DB,

   Your KW is similar to the old ZW, with slow breakers, CJack is giving you sage advise you will need a good breaker on each of the KW channels, along with TVS protection.

PCRR/Dave

If I buy a Legacy powermaster, will that do?  I understand it has circuit protection.  Again, I already have fast acting fuses between the KW and the track.

Thanks.

A Legacy Powermaster can vary track voltage remotely with the Legacy controller. I don't know about it's circuit protection. There was a thread on this some while back a couple months. I would think it does have fast protection. The Lionel product description does not mention protection.

Fast acting fuses are not as fast as electronic breakers. They have to melt and the time it takes to do that can melt other similar things too. In fact a fast acting fuse takes twice it's current rating to blow in a tenth second. A standard fuse, also considered not a slow blow fuse, takes twice it's current to blow in one second. They are 10 to 100 times longer than a fast electronic breaker.

DBH,

   The Power Master has no Circuit Breaker protection that I know of, if you have good quick breaking Resettable Breakers & TVS protection on each channel, you are good to go.

PCRR/Dave

This one seems to keep coming up, so, to answer as simply as possible,

For the cheapest solution for fairly good protection:  You want to use a 5 to 7 amp thermal circuit breakers.  one on the common side is ok, but placing one on each output as well (A/B on the KW) is preferred.  These breakers cost between $2 and $3 each from the large electronics suppliers.  In addition you should use 'TVS' diodes connected across the center and outer rail connections at each point where feed wires are connected to the track.  These protect the electronics inside your engines from high voltage spikes.  Such spikes come not only from the transformer, but also from engine motors, switch machines and accessories.  The TVS that is typically recommended here is the 1.5KE36CA, which cost less than 60 cents each.  

If superior circuit protection is wanted, that will virtually eliminate the threat of damaging things in a short, you'll want to look into electronics breakers.  The two best versions of these I am aware of are the PSX-AC, as others mentioned, which cost about $50 each.  The second is the breaker in Lionel's PH180.  These cost about $80, but would also replace your KW, providing a couple more amps to the track as well.  I'm unsure if one of these is any better in protection than the other, however the PSX-AC is adjustable, allowing you to set the trip point to any level you like.  With either option you still need the TVS as well.  

Mostly for Dave;  

With the TVS, it is important to remember that they are more effective the closer they are to whatever you are trying to protect.  The TVS inside a DCS TIU is there to protect the TIU from spikes, not to protect your trains.  Remember that electricity will take the path of least resistance. If that path is say, from a switch machine, through 20 feet of track, through the wiring and into the TIU and it's TVS, then that TVS will clamp the spike.  On the other hand, if the least resistive path is from the switch machine to the track, six inches down the track to the engine that just tripped auto-derail, up through the engine and through it's electronics then back down to the track again, that is the path it will take.  The absolute best place to install TVS is inside your engines.  Next best would be regularly spaced around the layout so an engine is never very far from one.  Placing them near switches is also a good idea.  The absolute worst place for them is all the way back at your transformer or TIU, though even that is preferable to nothing.  

On the other hand, many folks have been running for years without any TVS and have had no problems.  It seems that The TVS is mostly just cheap insurance as they are very inexpensive and can save you from expensive repairs, however uncommon such damage from spikes may be.  

JGL

JGL,

   I agree the engine is the best place for the TVS, however I have been using the TVS in the TIU for many many years without any problems what so ever.  Further I do use 5,7, & 10 Amp Scott type breakers between my KW & ZW Transformers & my TIU's, size depending on the Engine/trains, I am running on each given channel/track.  As of this time I have never damaged any engine or TIU setting up in this manner.  However if you want additional safety measures, you are always welcome to use further safety measures.  IMO they are pretty much over kill in most cases.

PCRR/Dave