Page 349 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

The National Electric Transportation Infrastructure Working Council (IWC) was formed in 1991 by the Electric
Power Research Institute with members drawn from automotive manufacturers and the electric utilities to define
standards in the United States; early work by the IWC led to the definition of three levels of charging in the 1999
National Electric Code (NEC) Hand book.
Under the 1999 NEC, Level 1 charging equipment (as defined in the NEC handbook but not in the code) was
connected to the grid through a standard NEMA5-20R 3-prong electrical outlet with grounding, and a ground-fault
circuit interrupter was required within 12 in (300 mm) of the plug. The supply circuit required protection at 125%
of the maximum rated current; for example, charging equipment rated at 16 amperes (“amps” or “A”) continuous
current required a breaker sized to 20 A.
Level 2 charging equipment (as defined in the handbook) was permanently wired and fastened at a fixed location
under NEC-1999. It also required grounding and ground-fault protection; in addition, it required an interlock to
prevent vehicle startup during charging and a safety breakaway for the cable and connector. A 40 A breaker
(125% of continuous maximum supply current) was required to protect the branch circuit.[5]: 9 For convenience
and speedier charging, many early EVs preferred that owners and operators install Level 2 charging equipment,
which was connected to the EV either through an inductive paddle (Magne Charge) or a conductive connector
(Avcon).

Level 3 charging equipment used an off-vehicle rectifier to convert the input AC power to DC, which was then
supplied to the vehicle. At the time it was written, the 1999 NEC handbook anticipated that Level 3 charging
equipment would require utilities to upgrade their distribution systems and transformers.

SAE
SAE J1772(2017) levels

Method Maximum supply
Current (A) Voltage (V) Power (kW)

AC Level 1 12 120 1.44
16 120 1.92

AC Level 2 80 208–240 19.2

DC Level 1 80 50–1000 80
DC Level 2 400 50–1000 400

The Society of Automotive Engineers (SAE International) defines the general physical, electrical, communication,
and performance requirements for EV charging systems used in North America, as part of standard SAE J1772,
initially developed in 2001. SAE J1772 defines four levels of charging, two levels each for AC and DC supplies;
the differences between levels are based upon the power distribution type, standards and maximum power.

Alternating current (AC)
AC charging stations connect the vehicle’s onboard charging circuitry directly to the AC supply.
• AC Level 1: Connects directly to a standard 120 V North American outlet; capable of supplying 6–16 A (0.7–
1.92 kilowatts or “kW”) depending on the capacity of a dedicated circuit.

• AC Level 2: Utilizes 240 V (single phase) or 208 V (three phase) power to supply between 6 and 80 A (1.4–
19.2 kW). It provides a significant charging speed increase over AC Level 1 charging.
Direct Current (DC)

Commonly, though incorrectly, called “Level 3” charging based on the older NEC-1999 definition, DC charging is
categorized separately in the SAE standard. In DC fast-charging, grid AC power is passed through an AC-to-DC
converter in the station before reaching the vehicle’s battery, bypassing any AC-to-DC converter on board the
vehicle.

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CITS : Power - Electrician & Wireman - Lesson 25