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Author Topic: AC or DC  (Read 10108 times)
Joe Satnik


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« Reply #15 on: March 09, 2013, 05:05:51 PM »

Dear All,

A good place for the TVS is across the lock-on, one lead to center rail terminal, the other to outer rails terminal.  Make sure it is bidirectional. 

Better yet, if you can afford it, install one in each of your locos, one lead to center rail pickup wiring, the other lead to frame or outer wheels pickup wiring.

In a previous calculation I came up with a 43 volt TVS. 

This seemingly high voltage allows  for "peak" instantaneous voltage

(20V RMS is about 28V peak) plus some allowance for TVS toleraces. 

(I was trying to avoid having a TVS on the low end of its "voltage tolerance" try to 'sink' the transformer's normal max voltage, ZWmax = 20V RMS.) 

If you don't go hog wild up to 20 Volts RMS AC, a 32 Volt TVS should work.   

Hope this helps.

Sincerely,

Joe Satnik
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If your loco is too heavy to lift, you'd better be able to ride in, on or behind it.
GSXR1000

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« Reply #16 on: March 09, 2013, 05:17:38 PM »

Interesting, I never looked into it.  Don't the new DCC decoders have this or a similar kind of diode protection?
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phillyreading

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« Reply #17 on: March 10, 2013, 11:49:47 AM »

Interesting, I never looked into it.  Don't the new DCC decoders have this or a similar kind of diode protection?

I think your question about DCC and TVS would be better answered on the H.O. forum. All I know about DCC is that it is generally used with H.O.trains, I could be wrong.
Being that most of us are into O gauge trains on this forum.

Lee F.
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r0gruth

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« Reply #18 on: March 10, 2013, 10:59:15 PM »

The HO folks operate with DC current and the O  three rail with AC.
I realize the 3R O actually runs on DC but some of the HO guys may
not unless they also do 3R O.
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Roger
GG1onFordsDTandI
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« Reply #19 on: March 12, 2013, 03:50:11 AM »

philly-read up on tvs. Its not just for dcc. The day your old thermal breaker contacts fuse, you want one.(Joe Knows, listen)

there are some other good current threads on dcc in O right now. interesting. But what I wouldnt mind seeing for us conventional guys would be radio controlled sounds for rolling stock mounting. cheap of coarse. non-molested engines, airwhistle, AND extra sounds. Sounds fun.

Torino- With the ZW you may never need another transformer. I replaced my cords recently and  after reading and experimenting, chose to polarize them to make use of them together in running blocks and accessories off the same common outside rail. they must be phased properly or will short. turning one plug 180 degrees is the fix. all my polarized plugs go into the polarized gfi power strip so all my commons connect. Now all commons can connect on all 6 transformers on any temporary layout making wiring simple safe and consistant enough for my 6 year old nephew to do alone. literally. No plug flip required. Bigger modern double flaired shaped plugs are easier to handle for the kid too. Keeps fingers away from plug blades.
A bad pic from the deepfreeze- A prewar Z (before ZW), a KW, three 1033's(one disguised as a Christmas tin), and a 80w(? anyone got a name for these no-nome Lionels). ALL now carry modern electronic safety, whistle rectifiers, customs tricks, and polarized plugs.
 
« Last Edit: March 12, 2013, 04:27:26 AM by GG1onFordsDTandI » Logged
phillyreading

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« Reply #20 on: March 12, 2013, 08:52:12 AM »

GG1onFords,

I did not state that TVS units were for DCC only! Please do not mis-quote me, what I was trying to say is that I did not know that DCC had a TVS unit inside it.

I know a little about the TVS units, they clip or hold the voltage to a pre-determined maximum voltage, something that a fuse or circuit breaker could never do. The TVS unit will protect against a momentary voltage spike and a fuse will just let it go thru.
A fuse or circuit breaker has to sense the overload condition before tripping, and with new electronic circuits in the newer engines you can fry something inside the circuit board in that short period of time. In this new electronic age you need almost instant protection fom voltage spikes and that is what a TVS will do.

The reason I mention about using a TVS unit is that your normal household GFI doesn't give any protection on the low voltage side(when you have a derailment) of the transformer because it protects only the incoming voltage. So you need something to protect your low voltage side as well.

Lee F.
« Last Edit: March 12, 2013, 09:05:26 AM by phillyreading » Logged
GG1onFordsDTandI
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« Reply #21 on: March 12, 2013, 01:27:26 PM »

Not quoting you! If I quote ver batum it will be in blue at the top. (or in quotation marks at least)  I wrote a statement giving you advice about something I thought you may have been interested in, but unaware of, because it is often only seen on digital command control layouts. It was intended in good faith. Not meant to offend. Tonino may have been a better choice for me to direct my response to, as this is his thread.  But you have nicely described the TVS better for all those who were unaware so I dont fully regret it.  Thank you. For sharing your knowledge Grin
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phillyreading

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« Reply #22 on: March 13, 2013, 01:44:46 PM »

I understand a little more about the common uses of TVS, but didn't know that it was used with DCC, maybe I too need to find out some info about the uses of electroincs in differant scale model trains.
In the O gauge area a lot of people are installing TVS units(at least three years now) to help with the voltage spikes that occur with a derailment and can damage newer electronics, especially the stuff in Lionel's TMCC & Legacy command control systems and MTH's DCS system for comman control.

Also with the older transformers in O gauge, you need to add in a circuit breaker for added protection because in most older transformers(1960's to 1985, maybe longer than 85) the circuit breaker mainly protects just the transformer and then not that well. Case in point; a post war 250 or 275 watt ZW, or a KW 190 watt will fry wire sizes under AWG 16 wire with a dead short before the circuit breaker pops off.

I know a bit about electrical work and trying to learn more about electronics, but will say that I don't know everything about elecrical work. I was NIASE certified auto tech for brakes and electrical, also went to vo-tech school for three years for electrical work in the mid 1970's. I also know about 3 phase electrical work and 3 phase motors.

Lee F.
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GG1onFordsDTandI
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« Reply #23 on: March 15, 2013, 02:05:08 PM »

No one knows everthing, someone will always know better than us, everone makes mistakes, usually by assumption. Embarrassed
We all have our own strengths, I'm trying to merge my career knowledge with my DCC knowledge too. The brake system testing you did will make it easier on you in a way. Your voc/schooling didn't do you any harm for sure, but nothing beats hands on experience. I learned video/vending and industrial HVAC controls, successfully, but self-taught on the fly, to put food in my belly. So my theory can be shaky. I had to find failed chips etc. and replace, more about logic than knowledge, but I learned along the way. Helped track down an IC control frequency glitch to whether power was from a Wye or delta source, but 3-phase motors are one of my weaknesses even though HVAC cert. I never did hands on 3-phase trouble shooting. Only swap-outs. Vending=1000 ways to build a circuit which did they choose that day? Think modern electrics are intimidating. One look in an old pinball machine vs new may change your perception. The old nightmare wires and relays once everywhere in free-for-all fashion, almost all disappear, everyting is still there but now miniaturized neatly on a circuit board.     Grin DCC, same thing, only different. Grin
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