J1772 Charging Standard Safeguards

[Zzzoom3]

It's my understanding that the EVSE uses the charging cable Proximity and Pilot lines to determine cable type and charging current. I'm wondering what the failsafe is so that you don't get zapped when connecting the cable if there's been a failure in the EVSE, EME, or KLE? There's obviously some protocol used before the switch that applies power is closed. Wondering how all that works.

Any electricians or Master Techs that understand how it works?

 

[jadnashuanh]

The EVSE pilot signal essentially gets returned to it through the EV after it modifies it to identify that it is there and ready. There's a voltage divider connected through the plug's switch handle to indicate that the plug is fully inserted. SO, the EV knows that the EVSE is connected, sees via the pilot signal what power it can provide, adjusts itself to not exceed that output current, and also indicates to the EVSE that the plug is actually inserted and locked because the release button is not being pressed to break that line. At least on my EVSE, pressing the release button drops out the power contactor immediately.

Lots of discussion on this at various websites, but one with some nice graphs and charts is: http://code.google.com/p/open-evse/wiki/J1772Basics