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How to prevent fuse blowing with big transformers?

L

Linnik

Flat Earth - Source First
I made this a public question as I think this is important question for many. Do not know if every country has the system we do in my country for the electrical assemblies but at least Germany and Scandinavia is uniformed in same manner.

We do have fuses in our house/flat electrical centre or table. No fuses on plugs like in U.K.

Now I am having newer flat with electronic thermal brakers which tend to be quite fast and sensitive.

Normal 230V sockets are fused by 11A fuses and the grounded ones are fused by 16A fuses.

TRANSFORMERS CARRIED IN NOW!

My DIY jobs apply huge transformers like a HiCap one or bigger. Also I have made trials with huge switching PSUs.

Switching ones are not problematic as they have slow start or relay start systems which can handle starting fuse friendly way.

But the transformers! I cut our brakers every time. Propably I have assumed few transformers to be broken even they are not for this reason.

I have tried to keep a breaker on by hand but then there blows the local fuse.

Now, one fault have obviously been that I have used only 5A fuse near the transformer (a HiCap uses 5A, slow, fuse BTW).

Should I try a bigger one, 10A, 13A glass fuse in the transformer box?? Then I will still have the house breaker problem..?

What would be the best solution to make these transformers to start at least once. Then they can stay on.. ??

Slow start modules?? Just resistors before them??

Or just go to smaller R-cores and enjoy the quality, not the power?

HELP ME PLEASE!! (Cos' I desire more tune!)

Oz
 
Is the equipment attached to your secondary windings switched off ? I have had this problem in the past and found that the best solution for me was to put the largest MCB/Fuse that i could safely fit (within voltage & current limits of any wiring , etc ) into the primary circuit, and then once it was up and running switch on the secondary circuit. I them kept the Primary permanently powered up and just switched the secondary circuit.

I suppose another ( heath robinson ) approach would be to parallel shunt the MCB using a heavy guage (slo-blo fused ?) cable with a switch just for start up and then once the Transformer had endergised/magnetised switch out the shunt wiring so that the normal running current went through the MCB. Just a potentially effective ( but ugly) idea.
 

Slow start modules?? Just resistors before them??
Click to expand...

Hi Oz
It seems that Les offers a slow-start module, so I guess this was already considered before.
cheers, Yair
 
Thanks Per Anders and Yair,

So you thing the solution would be a soft start module or modules in my case?

Thanks P-A, I got your link in the PM and it looks quite nice. Also Les's one is most tempting. Will think about them. Quite much components there is anyway.. But then, the switch could be a small, nice and cheap one.

It seems that I have to go that way..

However, Naim seems to handle it without ones in the HiCap, XPS and SuperCap?

Must say anyway, a friend's Hi-Cap blew brakers in my flat when we tried to start it.

Nobody should anymore wonder why Naim recommends to leave them on. They must have had many notices from customers from all over the world complaining the blowing fuses during the years.


Oz
 
To all the fuse blowers, ;)

Does anyone know good alternative fuse for NAIM ?

"regular" fuses sounds awful (slow bass),

silver fuses sounds OK but I can't found such at FARNALL :(


there are two alternatives-

1- To Have a nice stock of silver fuses.

2- To build/buy soft start - can be quite expensive and the extra relay contacts adds some impedance to the 220v rail.
(if you have more than 500VA transformer then you should soft start it)


Avi
 
2 I don't think any relay contacts in the mains circuit will cause you any trouble as long as you have contacts that are rated for the task.

I know that you point of view is not from an engineer rather an audiophile but lifes gets so complicated when the resistance from a relay contact compared the ordinary mains cable really creates a problem.

Sorry, I'm not an audiophile in that sense.
 
Hi all,

I have just bought one test piece of a device made for buffering the inrush burst of switching of a toroid.

It is made by a long established Finnish transformer manufacturer. It is a small, glue filled plastic box with only one input and one output connector by screw. It is also rated for 5A continual consumption. No relay switching it is.

Very cheap compared to. Around 33 UKP.

I am going to try it out and hope it at least gives me opportunity to test my rectification circuits.

Also bought some 10 and 15 A slow fuses.

(Very dangerous, sir!!! -Yes I understand, hands up! ;) )

Oz
 
No way!

I have now changed the local fuse to 10 A (no blows anymore), cut the transformer secondaries from any connections and put that "magic box" (see the photo) into the live cable between the fuse and the transformer.

House brakers do brake very willingly. If I leave the transformer's power cord connected and try to switch the house's thermal breaker on, it just refuse to connect the power.

I am starting to turn to Les's way in using smaller C-core or R-core transformers with higher quality but less VAs. For me it seems just impossible to use huge toroids in this house...

Or the other question is if Les's or Per-Ander's delay relay circuits would work. Comparing the prices against new, smaller C- or R-core transformers however they do not look very tempting.

Oz
 
dont forget not all circuit breakers are the same. go and buy some motor rated circuit breakers these allow for a for a short term high inrush of current and wont trip so easily, hope this helps
 
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