Electric Vehicle Power Transfer System Using a Three-Phase Capable Coupler
This document covers the general physical, electrical, functional, testing, and performance requirements for conductive power transfer to an Electric Vehicle using a Coupler capable of, but not limited to, transferring three-phase AC power. It defines a conductive power transfer method including the digital communication system. It also covers the functional and dimensional requirements for the Electric Vehicle Inlet, Supply Equipment Connector, and mating housings and contacts. Moveable charging equipment such as a service truck with charging facilities are within scope. Charging while moving (or in-route-charging) is not in scope.
SAE J3068 is a recommended practice for conductive charging of Electric Vehicles and Supply Equipment that utilize three-phase AC power. Presenting a symmetric three-phase load enhances grid stability, especially at high power levels. SAE J3068 standardizes an AC three-phase capable charging Coupler and digital control protocols, offering sufficient power and reliability for the commercial vehicle market. Existing technology is combined to provide higher power than existing charging solutions from the passenger car sector, with added diagnostics. DC charging on separate contacts with PLC controls is also described, as is limited three-phase AC charging with PWM controls, providing interoperability with J1772 protocols where possible.
SAE J3068 provides for the following:
A higher power version of an existing charge Coupler, for example 133 kW at 480 VAC 160 A three-phase.
Bidirectional digital communication between the Electric Vehicle and the Supply Equipment (EVSE) via single wire baseband signaling for local control, providing low cost, low complexity, and high reliability.
Grid supply voltage is signaled before the EV and Supply Equipment agree to charge. For example, in Canada 600 VAC is more common than 480 VAC but not all Electric Vehicles can utilize 600 VAC.
Independent control of current limits on a phase-by-phase basis. For example, this enables the minimum overall de-rate when only one phase leg has the available current restricted by the utility.
The EV may signal requested current, to enable a power management system to balance loads better. A minimum power requirement communication option supports fixed loads such as refrigeration, which cannot control current draw other than in an on-or-off fashion.
Only symmetric three-phase AC supplies are supported in this first edition (J3068 Edition 1). Asymmetric supplies such as corner-grounded Delta and High-Leg-Delta may be supported in a future edition.