Short answer: Electrical equipment that converts high-voltage grid power to the lower voltage levels needed by EV chargers at a charging site.
Explanation
A transformer is a piece of electrical infrastructure that steps voltage up or down. At EV charging sites, transformers step down the high voltage from the grid (typically 10-20 kV in Europe) to the lower voltage that chargers can use (400V or 800V for DC chargers, or 230/400V for AC chargers).
Larger charging installations often require a dedicated transformer, which is a significant capital expense. The transformer must be sized for the site's peak power demand, and installing one can require permits, civil works, and coordination with the local grid operator. Lead times of 6-18 months for transformer delivery are common.
As a driver, you might see a transformer as a green or grey box near a charging station, possibly fenced off. Some charging sites have the transformer built into the power cabinet. The transformer's capacity limits the site's total available power, just like the grid connection does.
Where you'll see this
- In vehicle specifications
Common confusion
Transformers at charging sites are not dangerous to drivers. They are sealed, insulated, and designed for outdoor installation. The fencing around them is a standard safety precaution, not an indication of unusual danger.
Example
A large Ionity highway station with eight 350 kW chargers typically requires a dedicated 2-3 MVA transformer, which can cost 50,000 to 150,000 EUR installed.
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