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[tico]

Hi all,

A bit of an odd question -- are any of the commonly available chargers able to function on 277V service?
 Has anyone done so?
Looks like a single phase of 277V@20A = 4.4kW (assuming 80% circuit breaker load and 1.0PF).

-t

[BrianTRice@gmail.com]

The DigiNow Supercharger v2 should handle it fine, but you should inquire about a controller customization to make sure the expected voltage range and current settings are defaulted for it.

[tico]

Thanks Brian, good to know.

Also, to begin answering myself -- apparently the spec sheet for the Delta-Q chargers specify 85-265VAC input range, so it comes up a wee bit short of 277V. Also, apparently their PF is .99 @120V and .98 @230V, which is pretty nice.

[Erasmo]

Wait a moment are those the measured voltages at you outlet?

[hubert]

Hello,

Please consider +/- 10% tolerance of the real grid voltage vs. rated voltage.

the upper limit of 265V for many devices is set for a grid voltage of 240V.

If your grid supplies 277V (rated), it means the real voltage can be >300V...

[frodus]

Usually this requires a completely range of components on the switching power supply end. 90-240V is one range, then it jumps up to something like 277 up to like 500VAC. SOME power supplies have an ultra wide range, and can go 90-300VAC, but it's rare.

[BrianTRice@gmail.com]

Excellent points. And on rechecking, I see the Elcon officially rates it for 265V AC input, which means you definitely need to inquire before buying:

http://www.elconchargers.com/catalog/item/9034090/10295140.htm

[Keith]

There is a trick for ac voltage reduction that might work for this. Using a 24 volt secondary transformer rated for the 20 amp current, you could buck the voltage down to 253 volts nominal. These transformers are cheap and readily available. The ac phase must be connected the right way to reduce the total voltage by connecting the 24 volt secondary in series with the 277 volt line.

[tico]

Wait a moment are those the measured voltages at you outlet?

Yes-- but not a common service outlet.  a single phase of 277V delivered on a L7-15 or L7-20 receptacle, typically for lighting purposes.

I have dreams of 3-phase 240/416V power outlets being commonly accessible, but alas, that appears rarely available in the Americas.

[tico]

There is a trick for ac voltage reduction that might work for this. Using a 24 volt secondary transformer rated for the 20 amp current, you could buck the voltage down to 253 volts nominal. These transformers are cheap and readily available. The ac phase must be connected the right way to reduce the total voltage by connecting the 24 volt secondary in series with the 277 volt line.

Cool -- I forgot about how common those little 24V transformers are.

 I suppose another option could be to just put two chargers in series, since 277v / 2 gives us 138.5V --- well within the 85-265V input range.

[Keith]

I'd worry about connecting two chargers in series. They would only share the voltage equally if both were under equal load at all times. If one turns on first it would be an unbalanced divider and the voltage rating might be exceeded. It might work fine but it's an expensive failure if it doesn't.

[MrDude_1]

I'd worry about connecting two chargers in series. They would only share the voltage equally if both were under equal load at all times. If one turns on first it would be an unbalanced divider and the voltage rating might be exceeded. It might work fine but it's an expensive failure if it doesn't.

it won't even "maybe" work like that.
first step in the inverter is to rectify and charge the caps.
then the PFC stage chops that DC pulse.

Even in series, you would pop the caps.

[Булгаков]

it won't even "maybe" work like that.
first step in the inverter is to rectify and charge the caps.
then the PFC stage chops that DC pulse.

Even in series, you would pop the caps.

Please excuse my ignorance, but I thought that in series, capacitor max voltage is added linearly?

[Keith]

I think a computer circuit simulation of two chargers in series with identical component values would predict a split of the source ac voltage equally in two, even after rectification. But real world tolerances of component values would cause many unbalanced events, especially during the initial transient power on. Enough unbalance between two chargers to "pop the caps" is very likely in my opinion. So in theory, yes the voltage would split linearly in two equal portions. In practice, have a fire extinguisher handy if you try it.

[MrDude_1]

it won't even "maybe" work like that.
first step in the inverter is to rectify and charge the caps.
then the PFC stage chops that DC pulse.

Even in series, you would pop the caps.

Please excuse my ignorance, but I thought that in series, capacitor max voltage is added linearly?

That is true until you start tapping loads between the caps. In this case the load is the charger, one on each cap. Its asking for all kinds of issues from things you cannot control directly.
It could be made to work, but not in a manner I would call safe.