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UMC Support 277v AC Power?
- Thread starter CCIE
- Start date
I you look at it, I believe that the specs may be on it. From the one picture that I can see, it is only spec'd at 100-240.
While it may accept it, getting it to understand what you want may be the harder thing. The adapter plug is programmed to set the UMC to specific parameters (i.e. the HPWC dip switches are hard coded in the rubber) and who knows what will happen.
Of course, try it, what could you lose?
While it may accept it, getting it to understand what you want may be the harder thing. The adapter plug is programmed to set the UMC to specific parameters (i.e. the HPWC dip switches are hard coded in the rubber) and who knows what will happen.
Of course, try it, what could you lose?
- the UMC?
- the Car? (or at least the converter)
- the house?
eprosenx
Active Member
Please see this thread:
Info from Tesla - 277v feed to Wall Connector (HPWC) - Which Cars Support It
Note that it seems like the UMC Gen 1 and Gen 2 did work for one person on 277v, but I really don't think that they officially support it and I am sure there are some NEC/UL issues with running 277v on NEMA 14-50 / 6-50 plugs / receptacles.
The Wall Connector did officially support 277v (fully documented), but then they removed it from the documentation. The reason I have been told they removed it from the docs was because it could cause flaky charging behavior on more recent model S and X units, so it was a user experience issue and not a safety or compliance issue.
Understood that there is no official support. I don't really have a use-case anyway, but was curious about support. Everything indicates that the car's AC charger will accept up to 300v, so it's just a matter of the EVSE handling the higher voltage.
277v NEMA outlets exist (NEMA series-7), they're just not common. Easy enough to build a 14-50 to 7-50 converter.
eprosenx
Active Member
Yeah, so I am dead curious to see a teardown of a UMC Gen 1 / Gen 2. Anyone have a dead one we can tear apart?
Specifically, I really want to know what the rating of the contactor inside the unit is to see if it is rated for 277v. There are other parts as well that might be meaningful as well (rectifiers for powering the circuitry, etc...) It could be that there is not enough separation between traces on the motherboard for 277v but there is for 240v. So basically it might work running on 277v, but not with the proper safety margins. <shrug>
Bad ass though! I might consider doing it in an industrial environment where I thought the penalty for failure if it melted was low. ;-) Not for your average home user though. ;-)
Electrical supply is rated +-10%. 240 +10% would be 264. Not far off 277....
eprosenx
Active Member
Yeah, though 277v + 10% = 305v. ;-)
277v is 15.5% more than 240v.
So it is not that far off, but I am not sure I would want to push those limits in my residence. ;-)
Thought I would bump this thread, since there aren't many about 277 Vac anyway.
UMC Gen 2 works fine with 277 Vac and my SR+ Model 3. There was a teardown of the US market UMC a while ago, and the relays are 277 Vac rated relays.
The AC/DC converters to power the charger's circuitry also works fine at 277 Vac. It's honestly very unusual to design power electronics that can handle 240 Vac, but can't also handle 277 Vac. Most power MOSFET used in AC/DC converters now days are rated for 600 V or higher anyway, so 277 vs. 240 Vac is hardly any more voltage stress relative to breakdown. Generally if a design can handle 240 Vac (+10% line regulation so 264Vac), it can handle 277 Vac. YMMV, I don't know if everything works fine if you are at the very extreme of line regulation, 305 Vac. My building supplies 274 Vac at the outlet, consistently.
Here's a picture of my charger working on a 30 A, 277 Vac circuit, using a NEMA L7-30 receptacle, and a pigtail to adapt that to NEMA 14-30 for my UMC Gen 2 connector.
UMC Gen 2 works fine with 277 Vac and my SR+ Model 3. There was a teardown of the US market UMC a while ago, and the relays are 277 Vac rated relays.
The AC/DC converters to power the charger's circuitry also works fine at 277 Vac. It's honestly very unusual to design power electronics that can handle 240 Vac, but can't also handle 277 Vac. Most power MOSFET used in AC/DC converters now days are rated for 600 V or higher anyway, so 277 vs. 240 Vac is hardly any more voltage stress relative to breakdown. Generally if a design can handle 240 Vac (+10% line regulation so 264Vac), it can handle 277 Vac. YMMV, I don't know if everything works fine if you are at the very extreme of line regulation, 305 Vac. My building supplies 274 Vac at the outlet, consistently.
Here's a picture of my charger working on a 30 A, 277 Vac circuit, using a NEMA L7-30 receptacle, and a pigtail to adapt that to NEMA 14-30 for my UMC Gen 2 connector.
208 Vac was what I was regularly charging off of. I generally charge at work, so we have 480/277 3 phase service, and an onsite step down transformer to 208/120. There were no convenient 480/277 outlets in range of where I park, so I had to use a 20amp 208 circuit for a while. Was quite painful, I wouldn't always be able to fully charge my rather far commute. That circuit had terrible voltage sag too, was usually 195 V by the time it got to the car. And I had to share it with a coworker who has a BMW i3.
Was nice finally installing a 277V circuit, especially today because my car got very low, 15%. First time I've ever been able to fully charge the car to my charge limit at work, despite it being at such a low state too! Plus no more sharing, BMW i3 can't charge off of 277V.
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