Skip to main content

So I'm probably going to annoy a few people by asking this, since there are two other threads about this, but I don't understand what these are and why I need them when I already have fuses for my old ZW's?

 

I mean, I know the fuses (and soon circuit breakers) protect me from shorts when I derail a train, but I don't understand the TVS. However, I figure it might be a good idea, since I had a board go a few months ago in my Porter without a derailment, and I'm still trying to figure out the cause.

Original Post

There are certain conditions where voltage spikes can occur.  I know this to be true, but I don't remember why so I'm hoping an expert will speak up as to the possible causes.  A TVS protects against these voltage spikes.  As per one of the other threads the effects of these can be cumulative, so there's a good possibility this is what happened with your Porter.  The circuit breakers are there to protect your transformers and your wiring, not your electronics.

 

Pete

Last edited by Texas Pete

A circuit break trips when there is a surge in current (like with a short).a TVS takes care of a transient voltage spike, which is a different. With a transient voltage spike the supplied voltage jumps for a very brief period, and there isn't a current surge that will pop the breaker or fuse.Such a spike can cause delicate electrical components to fry, or otherwise malfunction, especially true from what I remember in the day with CMOS components. 

You can purchase the TVS units for a very reasonable price at www.mouserelectronics.com  32 volt bi-directional is what I bought a couple years ago.

 

The TVS unit will clip the high voltage spike that goes through a fuse or circuit breaker because the fuse or breaker doesn't sense an overload. Voltage spikes happen very quickly and might be seen with a digital meter rather then with an analog meter.

Higher voltages then what the electronics are designed to handle will fry a circuit board. 

 

Lee Fritz

TrainsRME

 

Photo shows a $.50 TVS [Transient Voltage Supressor] connected directly between the "A" and "U" binding posts of a pw ZW. One needed for each power district. Creating a direct short across the Hot and Common conductors of the transformer throttle serving one power district.

 

I show this fuzzy photo to illustrate: 1] that it is  very inexpensive voltage spike protection, necessary if one is running electronic equipped trains, 2] this is a very simple fix. 

 

The best possible location of a TVS is in the engine where the fragile circuits exist, but few O-gaugers have experience or will attempt opening an engine and doing the critical wiring. The next best location is as close to the track as possible and on a Terminal Strip used to distribute railpower via multiple feeders to the rails of a single district.[photo 2]. This particular strip is plate jumpered to energize all terminal screws separately for Hot[green code] and for Common[white code]. Again, connected as a direct short, in this illustration across the secondary leads of a 180 watt PoHo..


Photo 3: TVS as they arrive from Mouser, Digikey,etc. Remember about $.50 each.

 

Keep in mind, over current trips breakers and blows fuses to protect the large investment in Transformers and in your wire runs. A voltage spike will not trip a breaker/blow a fuse. Breakers/fuses are wired inline on the Hot to capture and interrupt the overload----protect from overcurrent and both external Breakers or Fuses plus a TVS should be wired to each railpower district fed by the transformer, especially a pw ZW if powering electronic engines. 

 

Hope this helps....

 

IMG_2072

IMG_2071-001

 

Attachments

Images (3)
  • IMG_1762-001
  • IMG_2072
  • IMG_2071-001
Last edited by Dewey Trogdon

Hi Guys--  I know the part number for a TVS from Digi-Key :  1.5KE36CALFCT-ND   .....

But, I was trying to re-locate the part number from Mouser for the resettable circuit breakers..  Had it--Lost it..  Think it started with "655-....." something !!

 

Also, who has the correct "fast-blo" fuses (and part numbers, please) ??

Thank you all--in advance !!

 

KRK

Originally Posted by Dewey Trogdon:

Mouser 10 amp resettable breaker #.... thermal. Part number is on the breaker---just change 10 to 7 or whatever rating you need.

 

IMG_1763-002

These things scare me. Too much reading and not enough knowledge. I purchased a couple of 7A and never used them. The time to trip is rated at 2.2 seconds at 200%. Not the kind of thing that I wanted to protect my trains. Even at 7A it would theoretically be too slow 14A for 2.2  seconds would be the fastest. I suppose it's better than the ZW or older transformers, but not what I was looking for.

 

Do these (10A) actually trip if you jump a wire quickly like the PSX-AC demo?

 

Anyway, the whole thing spooked me, so I got  ZW-C with the 180W bricks. They trip like the PSX-AC.

 

The TVS are a little spooky, too. You really don't know when one has failed. They can fail and not melt and still show continuity. So, I just decided to change them once a year. But, it sure is something worth having and they have low fail rates, especially at the voltages we use.

 

The automotive blade type ATC fast-acting fuse may be the easiest to source. But, even the time to melt curve on those looks scary. I know when I short a power adapter socket in the car I can get quite an amperage surge from the battery, but our transformers are only 10A or so. Do they actually melt fast?  I know the AGX (glass tube\fast blow) type are getting hard to find.

 

Can anyone shed some light on my electrical ignorance?

Attachments

I built a 4 channel breaker box of Mousers 10 amp for one of my ZWs but soon gave it to a friend as I changed out 3 pw ZWs for five 180 watt PoHos on 5 power districts. [Layout now dismantled---Mar.'08].

 

The 180 PoHo's breakers are very quick compared to any others I have used. Now I only have two, linked to TPC 400s, serving on my small attic operation. Still have the very expensive QSI Powerguard protectors from the '90s but they are now for show with the blinking lights upon sparking, spikes,etc.

 

I rely on TVS for real protection since I sacrificed a spare PowerGuard [$85 each initially as I recall] for Dale Manquen to open and do autopsy on its capability versus TVS. His report was not encouraging regarding the PowerGuards.[photo: two QSI PG units mounted above Meters]]

IMG_1782

Attachments

Images (1)
  • IMG_1782
Last edited by Dewey Trogdon

OK, I am familiar with TVS Varistors and TVS Thyristors. As for a TVS Diode, that's a first for me. If I were specifying, I would have selected the TVS Varistor. Two items:

 

  • Since it's a Diode, isn't the TVS Diode polarity sensitive? I would have assumed that it would be. The TVS Varistor is not.
  • Does anyone care to expound on the relative benefit of the TVS Diode over other forms?

Gilly

Last edited by Gilly@N&W
Originally Posted by CarGuyZM10:
Originally Posted by superwarp1:

Transorb diodes are good(TVS), fuses are good.  But this is better

 

 

Now lets not get on these are too expensive kick, you guys are spending two grand on a engine what's a few bucks to protect it.

 

That's cool. Do they work as well for postwar and prewar trains. I know they spark in operation

They don't work well in conventional operation which is not an issue on my layout.  There only drawback.

Originally Posted by superwarp1:
Originally Posted by CarGuyZM10:
Originally Posted by superwarp1:

Transorb diodes are good(TVS), fuses are good.  But this is better

 

 

Now lets not get on these are too expensive kick, you guys are spending two grand on a engine what's a few bucks to protect it.

 

That's cool. Do they work as well for postwar and prewar trains. I know they spark in operation

They don't work well in conventional operation which is not an issue on my layout.  There only drawback.

Oh, okay. Thanks for letting me know. I run conventionally, so that rules these out.

Add Reply

Post
OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
330-757-3020

www.ogaugerr.com
×
×
×
×
Link copied to your clipboard.
×
×