I wonder by what sort of mechanism they "wear out" - given they don't have any moving parts as such. Feeding large long-hour switchmode loads is hardly novel - data centres for example I would have thought would provide a similar load characteristics as a large number of EV chargers, and I've heard of no problems with their transformers, and data centres have been about for decades. Maybe there's some peculiarity of the type of small pole mounted single-phase transformers the US seems to prefer for residential supplies - perhaps not rated for continuos load or don't handle harmonics too well (rattling the laminations or something like that)?

   - Andy.

Hello Andy:

A component doesn't have to have moving parts to "wear out" (that is become defective)..

Think about capacitors used in laptop computers which short out in the battery charging circuits.

My best guess is that is due to high operating temperature.

Peter Brooks

Palm Bay Florida USA     

Tap changers wear out at the moving contacts, but actual transformer failures are very rare.

On the UK grid we have some transformers that are pre-1970 still in service and buzzing along as good as new,

However, not all countries are so lucky - this paper from Kenya shows a 9% infant mortality with transformers, but reading further there are very definite causes, many related to poor quality control or underestimation of the final  load.

The main thing beyond installation and construction errors seems to be thermal overloading and then burnt oil and short circuits.

https://www.rerec.co.ke/assets/images/publications/Research-Papers/Analysis%20of%20Power%20Distribution%20Transformers%E2%80%99%20failure%20in%20Rural%20Electrification%20Projects%20in%20Kenya.pdf

The point about single and 3 phase may be relevant, the other feature of US installations, as I understand it, is an earth referenced HV so certain types of fault are harder to detect. The UK system has the equivalent of a big RCD on the HV network tripping on HV to earth fault conditions, allowing disconnection before currents become damaging. That and HV and LV fuses of course, but I think everyone uses those.

I note that Deepak has a number of publications on transformer designs and power convertors, , some in the last year or so, but they are on IEEE journals which I don't have access to. It might be worth trying to track that down.

I can well believe that increased thermal cycling is a thing that contributes .

Mike

The claim that multiple EV chargers on a single distribution transformer can reduce its lifespan from 30-40 years to as little as 3 years is alarming.

I think it is important to understand the details of the mechanism - we know for example that extreme thermal cycling can greatly shorten transformer life,

M,

Is there a solution to this ? Replacement  cycles as frequent as every three years are neither economically viable nor operationally sustainable, the carbon footprint associated with manufacturing these transformers probably outweighs the benefit of driving a EV 

I'd imagine, as we have no such issue yet reported in the UK, it  is something that depends heavily on the local transformer and network design and/or de-rating practice. The places to watch here will be the new transformers going in at motorway services and so on that are serving almost nothing but car chargers - I'd expect those to be the canaries in the coal mine if there is an issue - but most of those installations will be less than 5 years old at the moment.

Mike.

Raises the question of whether these challenges were thoroughly considered prior to the widespread installation of UK transformers for service stations etc

Hello Mike:

I didn't mention that within the same IEEE Spectrum magazine (pages 20-25) there is an article titled "Engineers transform transformers to save the Power Grid"- a global shortage of this essential grid tech bottlenecks energy projects" by Andrew Moseman.

It highlights that demand for transformers has spiked worldwide and so the wait time to get a new transformer has doubled from 50 weeks to nearly two years.

It also mentions the work being done on a Modular controller transformer (MCT) being developed by Divan and his team.

Peter Brooks

Palm Bay Florida USA

AMK said:

Is there a solution to this ?

I suspect the main solution is not to under-size the transformers.  You aren't going to get extreme thermal cycling if the transformer is operating within its rating.