EVSE welded contactor detector
In at least one embodiment, provided is an electric vehicle supply equipment having a line power contactor including a first line power input and a second line power input and a first line power output and a second line power output. It further has a welded contactor detector with a contactor sense circuit, the sense circuit having a first line shunt resistor network connected from the first line power contactor output to ground and a second line shunt resistor network connected from the first line power contactor output to ground. In another embodiment provided is an EVSE including a welded contactor detector with a contactor sense circuit having a bias resistor connected between the hot line relay input and the neutral line relay output.
1. An electric vehicle supply equipment comprising:
a) a line power contactor comprising:
i) a first line power input and a second line power input; and
ii) a first line power output and a second line power output;
b) a welded contactor detector comprising a contactor sense circuit, the sense circuit comprising:
i) a first line shunt resistor network connected from the first line power contactor output to ground; and
ii) a second line shunt resistor network connected from the first line power contactor output to ground;
c) a microcontroller connected to receive voltage outputs from the sense circuit, the microcontroller being configured to detect an amount of AC voltage present at the sense circuit after the line power contactor is commanded open by the microcontroller; and
d) wherein the microcontroller is adapted to:
(i) sample a voltage output from the sense circuit, the voltage output sample comprising AC and DC components;
(ii) determine a DC component of a set of samples of the voltage output from the sense circuit;
(iii) subtract the DC component from the voltage output sample to determine an AC component of the voltage output from the sense circuit; and
(iv) compare the AC component of the voltage output from the sense circuit to a threshold value to determine whether the line power contactor is welded.
2. The electric vehicle supply equipment of claim 1 , wherein the first line shunt resistor network comprises series connected first and second resistors, and wherein the second line shunt resistor network comprises series connected third and fourth resistors.
3. The electric vehicle supply equipment of claim 2 , wherein sense circuit comprises a first output and a second output, and wherein the sense circuit first output is located between the first and second series connected resistors, and wherein the sense circuit second output is located between the third and fourth series connected resistors.
4. The electric vehicle supply equipment of claim 1 , wherein the electric vehicle supply equipment is a fixed mounted electric vehicle supply equipment.
5. An electric vehicle supply equipment comprising:
a) a contractor comprising:
i) only one hot source line relay comprising an input and an output;
ii) only one neutral line relay comprising an output; and
iii) wherein closing the contactor closes both the hot source line relay and the neutral line relay and opening the contactor opens both the hot source relay and the neutral line relay;
b) a welded relay detector comprising a contactor sense circuit, the sense circuit comprising a bias resistor connected from the hot line relay input and the neutral line relay output such that the bias resistor has the effect of pulling the neutral line relay output up in voltage when the neutral line relay is open; and
c) a microcontroller connected to receive sensed voltage signals from the sense circuit, the microcontroller being configured to detect an amount of AC voltage present at the sense circuit after the contactor is commanded open by the microcontroller.
6. The electric vehicle supply equipment of claim 5 , wherein the microcontroller is adapted to indicate a failure of the neutral line relay if a signal above a predetermined threshold is not sensed at an output of the neutral line relay when the neutral line relay is commanded open.
7. The electric vehicle supply equipment of claim 5 , wherein the microcontroller is adapted to indicate a failure of the hot line relay if a signal above a predetermined threshold is sensed at an output of the hot line relay when the relays are commanded open.
8. The electric vehicle supply equipment of claim 5 , wherein the bias resistor comprises a resistance selected based on an impedance of an electric vehicle filter and charger.
9. The electric vehicle supply equipment of claim 5 , wherein the bias resistor has sufficiently high resistance to inhibit leakage current.
10. The electric vehicle supply equipment of claim 9 , wherein the bias resistor is at least 330 Kohms.
11. The electric vehicle supply equipment of claim 5 , wherein the electric vehicle supply equipment is a portable cord set electric vehicle supply equipment.
12. A method for providing a rapid determination of an open/closed status of a contactor in an electric vehicle supply equipment, the method comprising:
a) sensing a voltage level comprising AC and DC components at a contactor output;
b) detecting an AC component of a line voltage at an output of the contactor after the contactor has been commanded open comprising:
i) Sampling the sensed voltage level at the output of the contactor;
ii) determining a DC component of the line voltage from a set of samples of the sensed voltage level; and
iii) subtracting the DC component of the line voltage from the line voltage at the output of the contactor to determine an AC component of the line voltage at the output of the contactor;
b) comparing the AC component of the line voltage at the output of the contactor to a threshold value to determine whether the contactor is closed; and
c) indicating a failure to a user if the contactor is determined to be closed.