Overload protection?

trammayo

trammayo

Interested in vintage commercial vehicle, trams, t
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As some of you will be aware, my trailer based layout operates on batteries feeding the track (via a simple speed control).

I use a 3amp automotive blade fuse for protection and sometimes I go through fuses like shelling peas! Is there an auto reset breaker I could try in place of the fuse? I've tried searching but the only type that I can find is for AC up to 230v.

Fuses are cheap enough in bulk - its just a nuisance sometimes. I know what the main problems are in causing the overload/shorts (too many trains in operation, sharp curves and points coupled with errant pony trucks on the Bachmann locos - tried weights).

Anybody any thoughts?
 
Hi Tony - thanks for your reply. Looking at the RUE 300, it states the trip time is just over 10 seconds. Being as I am (mostly unaquainted with technology), is the Trip Time the length of time before it trips out OR the time it stays out before resetting? Also would it trip out immediately an overload happens?
 
Not sure about that trip time.
I use them only for overall protect as they do not trip instantly. Especially when cold. Run them close to max load for awhile so they heat up and then trip very fast when shorted out.

Reset happens when they cool down provided the short has been removed.

You can make a 3 amp load trip faster by paralleling 2 x 1.5 amp switches.
 
There's a 12v 3amp car overload switch. Brian Jones uses them with his speed controllers for battery set ups.
 
Mick,

I tend to use panel mounted 3 A resettable circuit breakers, IEC 934 Type RT/O, available from a local electronic supplier. They are marketted as "slow response" but under test when I had a direct short circuit using a bank of D cells they blew in about a second; the "slow blow" refers apparently to a continuous load above the rated power capacity; so it takes these 1 minute at 200% power, ie at 6A. They are reset by pushing in a red button which extends when they blow; they about an inch and a half or so long and fitted in a square hole of the appropriate size held by friction retainers

I have also used (internally in locos) 3A SPST circuit board mounted thermal breakers; these reset themselves when they cool after blowing. Their blowing charactaristics are rated as much the same as the others although under test the blow on short circuit seemed to be virtually instantaneous - at least, the delay was too short for me to measure. I don't know the exact time to restore power for these; it seems to be about 10 seconds but I didn't have the patience or the need to be precise about it.

Given your situation though I would have thought the "press to reset" type would be the better option of the two.

One thing to be aware of with any resettable circuit breaker is that they have lives; ie the power at which they will blow will decrease over time with the life usually expressed as a specified number of blow cycles before the rated capacity changes signficantly; typically however that is 500 or greater so it's not that much of a worry. I've occasionally had a problem although not, I must hasten to add, with trains!

Steve
 
;) I run my whole layout with a single 50 year old Hammett and Morgan controller that has a circuit breaker button, push to reset. That blows before my Train Engineer system, and it will also blow if I connect the TE the wrong way around.
 
Thank you for your responses!

Ian - I'll have a look at Brian Jones (should have thought of that in the first place!)

Steve - some interesting (and useful) information. Yes, you're right, I would be better with manual reset thinking about it :D. I need something pretty instant in reaction to a short or overload and was put off by the "time trip".
The "life" of the circuit breaker would mean it could last me six years!

Gavin - H&M - the Rollys Royce of controllers! I never had one but did borrow one for a day - the difference between chalk and cheese!

I'll continue to investigate. Meanwhile, I might have a look at fitting the odd check rail and maybe the frogs on the points (they cause the pony trucks to bounce and, depending on the speed, the trucks don't always return to the same position).
 
I remember Geoff Helm (of Helmsman Controllers) saying that the problem with designing a G Scale controller was actually putting a slight delay in the circuit trip, to allow for the nano second short circuits that arise when running in this scale.
 
Rhinochugger said:
There's a 12v 3amp car overload switch. Brian Jones uses them with his speed controllers for battery set ups.
Click to expand...
I think this is the one which Brian Jones uses.
Maplin have them in various values. Slow break for overload but immediate for short circuit

http://www.maplin.co.uk/p/16a-auto-reset-circuit-breaker-ak08j

Rik
 
I use this style; http://www.ebay.com.au/itm/Circuit-Breaker-Auto-Reset-1-5A-PCB-Mount-/390594945857?pt=AU_B_I_Electrical_Test_Equipment&hash=item5af145e341

But they used to be around $1 ea, cant find them on ebay for that now.
 
Tony Walsham said:
G'day Trev.
You sure know how to find the bargains. ;)
You can buy the same circuit breaker for A$6.95 from JayCar and A$5.50 from Altronics.
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As I said you used to get them for less than $1 on ebay.... I bought a lot of 10 for $8....
 
ge_rik said:
I think this is the one which Brian Jones uses.
Maplin have them in various values. Slow break for overload but immediate for short circuit

http://www.maplin.co.uk/p/16a-auto-reset-circuit-breaker-ak08j

Rik
Click to expand...

I looked at one of those but, as it was AC rated (and me lacking the knowledge), didn't think it was suitable.
 
trammayo said:
I looked at one of those but, as it was AC rated (and me lacking the knowledge), didn't think it was suitable.
Click to expand...
Its the current that trips them 1.5a @ 12v is the same as 1.5A @250V. What varies is/are the Watts. 18 Watts for 12V & 375 Watts for 250V. They work on the current heating a bimetallic spring, toooooo much current heats them up and they spring open... I have made a real balls up of this explanation no doubt I will be corrected....
I'll stick to making Marmalade in future....
 
Cheers Trev. Me understandy bit more now. Yesterday (at a Fair Day in Killala) I didn't blow one fuse - apart from my own ;D
 
trammayo said:
Cheers Trev. Me understandy bit more now. Yesterday (at a Fair Day in Killala) I didn't blow one fuse - apart from my own ;D
Click to expand...
What amazes me is that my explanation must have been on the money......
 
gregh said:
So what did you finally use to stop the fuse blows?
Click to expand...

I don't know - just luck (and more observation!). Yesterday I blew 8 (one was an overload). One of my more recent purchases has a habit of derailing on a trailing point. It is light on the pony truck and, because it pivots on a swivelling arm, has the ability to step virtually outside the loco. May have to modify points somehow. I put some lead under my very recent purchases (annies) and no derailments whatsoever. It is the gaps in the points - the small wheels bounce. I'll have to raise the bottom of the groove (tramway fashion).
 
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