science

SAE J3068

SAE J3068 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand SAE J3068 rather than just read about it. In short: SAE J3068 "Electric Vehicle Power Transfer System Using a Three-Phase Capable Coupler" is a North American recommended practice published and maintained by SAE International. J3068 defines electrical connectors and a control protocol for charging electric vehicles.

Key takeaways

SAE J3068 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SAE J3068 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SAE J3068 from memory before moving on to harder problems.

Reference excerpt

SAE J3068 "Electric Vehicle Power Transfer System Using a Three-Phase Capable Coupler" is a North American recommended practice published and maintained by SAE International. J3068 defines electrical connectors and a control protocol for charging electric vehicles. It has the formal title "SAE International Recommended Practice J3068". J3068 defines a system for conductive power transfer to an electric vehicle using a coupler capable of transferring single-phase and three-phase AC power as well as DC power, and defines a digital communication protocol for control. J3068 also specifies requirements for the vehicle inlet, supply equipment connector, mating housings and contacts.

History Initial discussions in the Electric Power Research Institute's Infrastructure Working Council meetings regarding issues related to three-phase charging in North America led to the development of J3068. There was a lack of non-proprietary, UL listed equipment that could be legally used in the United States. Some large electric vehicles were being charged without using ground fault protection, and without connectors that automatically de-energize when disconnected from the vehicle. Therefore, SAE authorized a new task force to develop a standard that focused on heavy and medium duty applications, and more generally any vehicle charging at commercial and industrial locations or other places where 3φ power (three-phase) is available and preferred. Early within the development of the standard, it was decided that the J3068 connector and inlet would expand upon Europe's IEC 62196 type 2 connector also known as the Mennekes connector.

North American application J3068 states that it aims to cover three-phase equipment which meets applicable North American listing standards. The core standards for Electric Vehicle Supply Equipment in North America are tri-national standards for Mexico, Canada, and the United States. See CANENA. They are essentially equivalent documents with different names in each country.

The J3068 connector is mechanically identical to the Type 2 connector, because it makes direct references to IEC 62196-2 and -3. Additionally, SAE J3068 supports voltage ratings which align with North American grid voltages and EVSE standards. Given that a 480Y/277 VAC three-phase wye-connected four-wire supply is a common configuration supplied by utilities at commercial locations – under SAE J3400 and SAE J3068 the implied higher rating is taken; thus allowing single-phase charging at 277 VAC nominal for North American application. Also, SAE J3400 electric vehicles in North America are required to support power transfer under PWM-CP at 277 VAC. Under SAE J3400 and SAE J3068 EVSE cannot use PWM-CP controls when nominal system voltages exceed 480Y/277 VAC (single-phase 277 VAC). digital communication (e.g. LIN-CP) shall be used when these voltage limits are exceeded (e.g. 600Y/347 VAC – chiefly Canadian).

Digital communication for AC charging (LIN-CP)

Basic AC charging is defined in SAE J1772 and IEC 61851-1 Annex A with an analog control pilot, and is used with a variety of single-phase AC grid voltages lower than 250 VAC. LIN-CP (Local Interconnect Network on the Control Pilot) was originally specified in IEC 61851-1 Annex D in Edition 3. Unlike PLC over Control Pilot (ISO 15118-2), LIN CP is designed to be a low-cost digital upgrade for the analog PWM controls. The control protocol is a variation of LIN which retains the analog voltage level signaling from SAE J1772. The positive level of the LIN signal waveform can change from 12 volts to 9 or 6 volts (known as State A, State B, and State C in J1772). An earlier version of this LIN-based control protocol was published in Annex D of IEC 61851 edition 3. Major contributors to the development of this protocol include ABB in Sweden, the University of Delaware, Vattenfall Sweden, Mack Trucks/Volvo Trucks North America and others. The description of the control protocol in the 2018 edition is written from the point of view of a developer using a commercial LIN development package with API support for LIN functionality (which is familiar to embedded controller programming teams in the automotive industry). The behavior of the EV and EVSE are described separately in terms of the signals they can see on the API. The details of how the LIN signals are sent between the EV and EVSE are assumed to be handled by commercial LIN software. IEC 61851-1:2017 Annex D does not presume that a commercial LIN development package is used to implement the standard. It leaves the decision how to implement the standard to the developer. Differences in logic and nomenclature between J3068 and 61851-1 Annex D are detailed in J3068 (2018) Appendix F. LIN-CP is similar to the approach used by Tesla based on J2411 (Single-wire CAN), but maintains the CP voltage levels from analog PWM to be compatible with existing EVSE safety models. LIN transceivers used for J3068 must have an extended supply range. For example, the TI SN65HVDA100-Q1 operates from 5V to 27V. The extended voltage range is required because the LIN transceiver must operate when the Control Pilot is at 6V level (similar to "State C" in J1772). The 2022 edition of SAE J3068 recommends a slightly different Pilot circuit from the one defined in SAE J1772 to improve compatibility with PWM signaling.

Compatibility

SAE J3068 has additional requirements on the coupler proximity circuit (aka vehicles with Type 2 inlets in North America) that allow them to be interoperable SAE J3400 and SAE J1772 EVSE for both AC and DC power transfer which monitor proximity. Also, SAE J3068 has additional requirements on the infrastructure proximity circuit (aka socket-outlets EVSE in North America) that allow them to support 48 A carry-along cable assemblies. Both side of the proximity circuit can optionally support 12V power-over-prox (see SAE 3068/2). SAE J3068, references SAE J3400 for DC power transfer with the appropriate adjustments for the coupler proximity circuit. Depending on the topology of the vehicle on-board charger, it may be possible to charge from a J1772 EVSE using an adapter. While adapters are not ideal, manufacturer specific adapters might be useful and are allowed in some countries according to IEC. Such an adapter should be rated for 80 amperes, as there is no practical way to signal the adapter's current rating.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with SAE J3068

Start with the simplest possible case. Write down what SAE J3068 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SAE J3068 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SAE J3068 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SAE J3068

In research: SAE J3068 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SAE J3068 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SAE J3068 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Automotive standards, Automotive technologies, Charging stations, so understanding it makes those chapters shorter.
In everyday life: Look for SAE J3068 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study SAE J3068 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SAE J3068 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SAE J3068 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SAE J3068 in simple terms?

Why does SAE J3068 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SAE J3068?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SAE J3068.