Transformer Sizing Calculator for Arkansas
NEC 2020 transformer sizing math for EV charger installers working in Arkansas.
DCFC and large workplace EV deployments in Arkansas typically need a dedicated 480 V three-phase service, which means sizing a pad-mount or dry-type transformer against the connected charger load plus the NEC 2020 continuous-load multiplier.
Worked example for Arkansas
A 180 kW DC fast charger draws roughly 217 A at 480 V three-phase. Applying the 125% continuous-load factor (180 × 1.25 ≈ 225 kVA), then rounding up to the next standard transformer rating gives a 225 kVA minimum. Arkansas's 96°F summer ambient does not directly derate the transformer, but it does push the secondary feeder ampacity down by 0.82× — so the secondary copper has to be sized accordingly.
Code & Utilities
Arkansas currently enforces the NEC 2020 edition, adopted in 2022. That includes Article 625 (Electric Vehicle Power Transfer System) requirements: 125% continuous-load sizing on EVSE branch circuits, GFCI protection at outdoor receptacles, and provisions for energy management systems on shared circuits.
Major electric utilities serving Arkansas include Entergy Arkansas, Southwestern Electric Power, Arkansas Electric Cooperatives. Always verify the applicable tariff and any utility-specific requirements (CT cabinets, metering enclosures, demand limiters) at design time.
Climate & Ampacity
Plan EV feeders against a 96°F ambient in Arkansas — the resulting NEC 310.15(B) correction of 0.82× is what trims a #6 THWN-2 down to its true continuous rating. Because the correction is below 0.9, conductors that "look fine" on a 30°C ampacity table will not carry their nameplate current here — always derate explicitly.
Arkansas takeaway
Coordinate primary-side voltage, impedance, and fault-current specs with Entergy Arkansas early — interconnection lead times for new pad-mounts in Arkansas can run 6-12 months on commercial DCFC sites.