TIU voltage & fuses questions

Todd, seems like the logical place for them, but them manual says on the input... not sure why.

Ed

Current in a circuit is everywhere the same, so it doesn't require fuses to be nearer the short.  Putting them on TIU inputs serves to afford their protection to the TIU.  Note there is a chance for a short on the output terminals themselves if a thumbscrew loosens.  There of course, is also the possibility of some interior failure in the TIU

Think of the power supply as a big hammer,(post war ZW) If there's a short anywhere on the layout,  the power supply wants to surge and make up for lost power at the short. If the short is on the track side of the tiu the power surge is going through the tiu. However if a fuse is between  the power supply  and tiu the power surge can't get to the tiu.

Not sure which is best, so I may put a fuse on the "in" and the "out".

Gregg, when I think of fusing stuff, I think of house wiring.  When I plug something into a house outlet, the fuse is ahead of the appliance, in the service panel. But if my TV didn't also have a fuse, a minor short in the TV wouldn't blow the house breaker, but the one in the TV would.  Hmmmmm.  Then again, I'm not sure which side of the transformer in the TV the fuse is on!  Not arguing, just intrigued!

I'm hoping for a response or two on the bigger question.  Can I get away with a 24V transformer feeding the TIU?  It would be about (only) 10% over specification. I did find a post on a HO forum that suggested that feeding 25V DC was OK in a DC environment.

Anyone?????

Ed

Circuit breakers:  I use 10 amp circuit breakers on each input to the TIU.  I also have 5 amp circuit breakers on each TIU output.

Since I also use a ZW for conventional power I have a 5 amp circuit breaker on the ZW output.

I have 10 power feeds to my track (individual blocks).  I also have individual 3 amp circuit breakers on each power feed. The reason for the individual circuit breakers on the power feeds is to trip each circuit independently if a derailment occurs and an overload occurs.

Ed, the fuse in your TV would be lower amperage rating than the house circuit and therefore would blow first.

The peak voltage in an AC circuit is much greater than the given voltage.  For example, peak voltage on your 120-volt house circuit is in the neighborhood of 170 to 180 volts.  On a DC circuit the peak is the stated voltage.

Peak voltage is about 1.4 * RMS voltage, so that 22 volt RMS AC signal would be about 30.8 volts peak.  That's probably why the 25 volts DC was considered "safe".  Personally, I keep it well under 22 volts AC and I don't use DC on the TIU...

RJR has explained it well for the fuse.  Even Lionel made a harness with a fuse on the input side to use a PW transformer with the Power Master.

I think John has a valid point on the peak voltages and the effect on the TVS in the TIU.  Also the components inside can be rated for a certain voltage.  You are really on your own, but the risk is significant.  Loss of TIU and possibly PS-2/3 engines with the high voltage.  G

Gentlemen,

  I set up pretty much like Pro Hobby with the 10 Amp and 5 Amp Breakers.

The Scott Breaker banks work great for my layout, never damaged anything

and the breakers are easy to quickly reset. 

PCRR/Dave

PCRR/Dave,

Your post is the second mention of the Scott Breakers and Breaker banks.  do you have a source for these?

Thanks in advance...

David

TRAIN ELECTRICS LLC sells all of the Scott's Odds-n-Ends products now.

David,

   Gunrunnerjohn is corect, Scotts is now TE, been doing this so long companies have been bought out and renamed.

PCRR/Dave

Scary, isn't it!

Gun Runner,

    Yea it use to be so simple back in 1949 - 1950, the Tin Plate worked no matter what way you connected it up, the O guage tubular track was new then and worked quite well, pins and all.  Wish I could go back to when some of those train stores were still around.

Heck even the old Iron Horse Hobby Shop is gone now.  I really do miss Frank and the Train Club, Christmas is not quite the same without spending time with him and his office layout. 

PCRR/Dave

The TIU I think has a 33 volt TVS. So 22 volts peaks a bit lower than that. Also many chips are and capacitors used are rated at 35 volts. 24 volts would peak at 33.6 and fry the TVS.

Running the DCS at 12 volts will work electrically but there are considerations. The problem is, is that lower voltages require more amperage to do the same amount of work in wattage. Lets say we have a load of a train using 120 watts. This can be 12 volts at 10 amps or 20 volts at 6 amps. Pulling a long train under heavy load may pull more amperage than the chips are designed for,if for example if a Triac is rated at 6 amps running the motors. 

Dale H

Dale, be wary when comparing voltage & amperage of AC & DC circuits.  It's not a straight Ohm's law calculation.

http://hyperphysics.phy-astr.g...ctric/acohml.html#c1

I know,I was just trying to keep it simple. Still running on 12 volts would increase required amperage.

Dale H