Can my step-up/down transformer be repaired?

[martin18]

Hello there, I brought a 5000W step up/down transformer with me for my appliances when I moved back from the US earlier this year. I'm living in an old house, don't think the wiring is up to much, and from the beginning the transformer would trip the circuit board switch, though I could just flip it back on and it would work (sometimes after a few tries at flipping).

The other day, though, there was a loud bang and not only did the circuit trip but the transformer stopped working. It's strange because there is a red power light on the transformer yet there is no power going to the appliances plugged into it. The transformer has a circuit breaker rather than a fuse, and pressing the breaker does nothing.

Wondering what is wrong with it and whether it could potentially be repaired given that it wasn't exactly cheap? Or am I just going to have to bite the bullet and get a new one?

Thanks for any advice you can give!

 

[Pete999]

Hello there, I brought a 5000W step up/down transformer with me for my appliances when I moved back from the US earlier this year. I'm living in an old house, don't think the wiring is up to much, and from the beginning the transformer would trip the circuit board switch, though I could just flip it back on and it would work (sometimes after a few tries at flipping).

The other day, though, there was a loud bang and not only did the circuit trip but the transformer stopped working. It's strange because there is a red power light on the transformer yet there is no power going to the appliances plugged into it. The transformer has a circuit breaker rather than a fuse, and pressing the breaker does nothing.

Wondering what is wrong with it and whether it could potentially be repaired given that it wasn't exactly cheap? Or am I just going to have to bite the bullet and get a new one?

Thanks for any advice you can give!

MAKER AND DETAILS NEEDED or pic sorry for the caps

 

[martin18]

MAKER AND DETAILS NEEDED or pic sorry for the caps

Thanks for asking Pete

https://www.amazon.com/gp/product/B07MP1NVH1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[DPG]

If it went with a big bang then the chances are the switching transistors inside the unit have gone pop. This would be terminal unless you are experienced at repairing this kind of thing.

 

[pc1966]

As above, a bang normally means very bad news.

That is very small for a "real" 5kVA transformer so it is almost certainly a switching converter and they tend to fail with a bang and I doubt you could get it repaired for anything under half its price as a starting point (even assuming they can get a service manual for it). Working on SMPSU is hazardous, so unless someone is really competent (electrically speaking) and adequately prepared for such high voltage / high energy work it is not something to do.

So really you are looking at a new unit I'm afraid

 

[martin18]

If it went with a big bang then the chances are the switching transistors inside the unit have gone pop. This would be terminal unless you are experienced at repairing this kind of thing.

Thanks DPG, it was a big bang so I imagine that's it. Just out of interest, what would have caused this? Why didn't the circuit breaker protect the transformer?

 

[DPG]

Thanks DPG, it was a big bang so I imagine that's it. Just out of interest, what would have caused this? Why didn't the circuit breaker protect the transformer?

Overload, or just a random occurrence which can happen with these type (switching regulator) of devices. They aren't actually transformers in the conventional sense.

The circuit breaker may not have actually seen an overload if it was a circuit fault.

 

[pc1966]

Unfortunately semiconductors are very small inside, so they have a limited ability to get rid of large amounts of heat quickly. Basically they are faster "fuses" than most fuses are!

You get special very-fast acting fuses to protect semiconductors, but even then you don't always stop damage but you do stop a fire or explosive ending (if very high power system).

Circuit breakers let through a lot more energy than fuses usually do, so they are utterly useless to stop semiconductor damage. But more often than not it is the semiconductor failing due to voltage stress or similar that is the reason so the breaker firing is more to stop a fire, etc.

 

[pc1966]

If you have a spare half hour this might be of a little interest:

 

[martin18]

Unfortunately semiconductors are very small inside, so they have a limited ability to get rid of large amounts of heat quickly. Basically they are faster "fuses" than most fuses are!

You get special very-fast acting fuses to protect semiconductors, but even then you don't always stop damage but you do stop a fire or explosive ending (if very high power system).

Circuit breakers let through a lot more energy than fuses usually do, so they are utterly useless to stop semiconductor damage. But more often than not it is the semiconductor failing due to voltage stress or similar that is the reason so the breaker firing is more to stop a fire, etc.

Thanks so much to you all. Given that I have to buy a new one and I'm not leaving this old house any time soon, how can I protect it against this happening again, do you think? It'll be a 3kVA one this time, I think.

 

[Marvo]

According to the Amazon listing that thing is about 8 kilos so I'm guessing it's a wire wound step down transformer inside rather than a switch mode type supply.

Any normal sparky should be able to bench test it to figure out what the fault is and transformers can be rewound if necessary but it's a job for a company that's geared up to do that kinda thing. Maybe a motor rewinder could do transformer repairs, it's fairly similar work although it's doubtful they'd have machinery so they'd probably have to do it by hand.

As for why it went faulty in the first place...you'll get a much better idea of that if you get someone to bench test it and know what the actual fault is. It might be as simple as an internal cooling fan that's no longer working or damage by chronic marginal overload but, not having seen the inside, this is guesswork.

 

[DPG]

According to the Amazon listing that thing is about 8 kilos so I'm guessing it's a wire wound step down transformer inside rather than a switch mode type supply.

Any normal sparky should be able to bench test it to figure out what the fault is and transformers can be rewound if necessary but it's a job for a company that's geared up to do that kinda thing. Maybe a motor rewinder could do transformer repairs, it's fairly similar work although it's doubtful they'd have machinery so they'd probably have to do it by hand.

As for why it went faulty in the first place...you'll get a much better idea of that if you get someone to bench test it and know what the actual fault is. It might be as simple as an internal cooling fan that's no longer working or damage by chronic marginal overload but, not having seen the inside, this is guesswork.

Must admit I assumed it was an electronic converter, but perhaps not. In that case I wonder what went bang?

 

[Marvo]

Must admit I assumed it was an electronic converter, but perhaps not. In that case I wonder what went bang?

You might be right, I was just going on the weight which is only one step up from blind guesswork. It sounds from the OP that whatever did go wrong was failing over time and causing occasional tripping before it eventually went big badda boom. From experience things semiconductor have more of a tendancy to go pop one-time without warning, things wirewound might be more prone to deterioration over time but again no proof.

 

[martin18]

Honestly I think the wiring in the house is to blame probably. Before the transformer arrived the circuits in the house did trip a few times with normal appliances. With the transformer, though, it was every single time I plugged it in.
Given that, really hope one of you can recommend how I can protect a new transformer from the same fate.
Thanks a million.

 

[pc1966]

According to the Amazon listing that thing is about 8 kilos so I'm guessing it's a wire wound step down transformer inside rather than a switch mode type supply.

Good point - I was basing it on the visual size. Even so, at that sort of new price I would doubt that you could get it rewound economically.

 

[pc1966]

As to why the transformer went bang - it could just be a duff component in it, or sometimes it is provoked by a spider or similar shorting stuff out and causing an arc (which is the high current bit that does the damage, the spider is long gone by then).

You mention the house electric tripping, that is something to have investigated as it might just be a serious issue. Do you know if it was the MCB (over current) breaker that trips, or the RCD (earth leakage) one?

Transformers do draw a high inrush current so can trip MCBs and thinking about it if that really is a 5kVA transformer it would need a dedicated supply and not a 13A plug! Basically 5kVA is about 22A for 230V and usually you would be looking at something like a 32A D-curve MCB or BS88 fuse for it.

 

[pc1966]

OK I looked at the device again and it is not a 5kVA transformer, the continuous load is 1500W so weasle wording from the advertisers once more:

"This model has up to 3000 Watt Maximum Capacity (110/120V <> 220/240V) with super-quiet performance.

MAX - 5000 Watt for 30 Mins Use. For continuous use: 1500W. Make sure you multiply x2 the wattage of your item and get a transformer bigger than that"

So it can be used from a 13A plug and is probably OK for a ring final that has the usual 32A B-curve MCB on it, but it is hard to say for sure if it would be trip-prone on inrush current. Just noticed you are in Ireland, maybe if in ROI your house has more radials with 20A MCBs? They would be trip-prone here. Perhaps @Risteard or @Edmond Noonan might have some insight on this aspect.

I would get a professional electrician in to take a look at your house electrics just in case.

 

[Lucien Nunes]

It's too heavy to be electronic and too light to be 5kVA. It's probably a cheap nasty wirewound autotransformer rated lower than even their lowest claim, knowing that in domestic use it might not see any heavy loads. They specifically warn you against using it to supply heating loads, but most domestic loads >1kVA are heating loads. You can't get 5kVA out of it using one 13A socket at 230V or two 15A sockets at 115V anyway. In step-up mode, how you are supposed to feed it 5kVA via one 15A 115V plug even for half an hour is a mystery.

Cheap, nasty transformers that skimp on iron are also more likely to trip breakers on inrush, because they saturate magnetically for a longer fraction of the mains cycle. It's probably also wound for 220V and starts losing its spring at 240 anyhow. I would fully expect something like this to be prone to tripping a B-type MCB. A professional grade item would be more like £500 and weigh 25kg+.

 

[Taylortwocities]

At $100 just for shipping, try and find one supplied from the UK!

 

[static zap]

Maybe buy a "Local" replacement of 1 of the heaviest wattage appliances with one .. so the transformer has less work to do.

Big motor appliances cause start-up surges that may -eat into the life-expectancy of a replacement.

Larger continuous heating applinces cause gradual overheating build-ups.

Just a strategy thought. Good Luck.

 

[martin18]

Thanks a million everyone, this is all really good. Though I'm afraid I'm a total novice so had some trouble understanding some of the more complex advice...

I think the wiring in the house definitely needs to be looked at, but this is an "as is" rental so that rules that out.

In terms of appliances, in fact the transformer alone -- without any appliances connected -- trips the circuit.
*Given that, any specific ideas about what I could do, if anything, to protect a new (cheap) transformer?*

Planning on getting a UK "3kVA" one of the same type.

When the appliances are plugged in, generally what I have is a high-end coffee maker that is heating and in use for a total of about 10 minutes, 2 or 3 times a day. I have quite a few other appliances I use with it occasionally but the coffee maker is the only consistent one and is basically the reason I bought the transformer in the first place.

 

[ETinIL]

HI - I have a partially similar issue and would appreciate any guidance.

I bought a 3000 watt step down transformer which a friend brought over to me in Israel. My place has updated modern wiring and can handle plenty of power.
The first time I used it - it worked fine.
The second time I used it, just by plugging it into the socket, it blew all the power in my apartment. I changed sockets and it did it again

ELC T3000 brand.

Any ideas if it fixable or is just now a heavy paperweight?

Thanks Eric

 

[Taylortwocities]

What did it blow? RCD, MCB, fuse?
What electrical test equipment do you have?

 

[Lucien Nunes]

It might just be tripping on inrush, and not actually faulty. As above we need to know the exact spec of the breaker that is tripping.