A Voltimum user has a query of the most appropriate transformer to install and what questions to ask before contracts are drawn up...
This Q & A is one of thousands posted in our Technical Expertise area, and answered by our Voltimum Experts.
Question:
I am working on a project where our standard specification asks for a transformer (which feeds main LV Panel) with:
No load voltage: 433 V
Windings: Copper
Impedance: 6%
Type: Corrugated tank
The contractor has advised that the standard transformer, which is more readily available would be:
No load voltage: 415 V or 433 V (but only 415 V ones in stock).
Windings: Aluminium
Impedance: 4/4.5%
Type: Bolt-on Radiators
I am unsure if what he is proposing to install is appropriate so I thought I will ask an expert for his thoughts or to highlight the pros and cons before I agree to anything.
Answer:
Gary Parker
To be honest, it is impossible to comment. Both transformers will be, no doubt, manufactured properly with the appropriate standards applied so it will come down to three things:
- Whether the transformer is appropriate for that particular install.
- What are the individual pitfalls of each transformer?
- Cost.
Aluminium transformers are sometimes cheaper and, depending on insulation, can have a similar life span.
The lower impedance will impact your fault current levels, so it would be worth ensuring that your downstream OCPDs are adequate.
Personally, I would draw up a comparison table with things such as size, initial cost, lifespan, fault rating, maintenance etc. and pick the one that ticks the most boxes.