460V equipment, 208V supply 8

[QGeek]

Our machinery normally uses 460V, 3-phase supply. We have come across an instance where customer only has 208V, 3-phase, and not a hope of changing. I am in the process of converting the equipment. Someone suggested wiring the 460V motors in the delta configuration. Any advice?

 

[jraef]

Ok, thanks Don, good to know. I don't have a copy of the 2014 NEC yet, I live in California so we will not likely adopt it until 2018 or 2019... I got that information from an internal company review of significant changes coming up that may affect the equipment we build.

racookpe1978,
As I understand it, the utilities do not have to let just anyone willy-nilly connect a grid-tie solar system to their pole pigs anyway. You must apply for, and be granted, a "Net Metering" contract/license/permit (not sure of the vehicle), in which you must show compliance with all the regulatory issues involved in putting power back on the grid. In that process, the utilities must be also evaluating their equipment themselves, because I know of a couple of people who were denied Net Metering because the utility claimed their equipment was incompatible with reverse-feed and would be too expensive for them to replace. Might have just been a straw-man, wouldn't put it past them to do that, but it also might be real.

"Will work for (the memory of) salami"

 

[bacon4life]

racookpe1978
Since the inverter has to have a hot line to start production, inrush from the low side doesn't happen.

In the past, the amount residential solar was very small compared to the capacity of the distribution circuit, so the simple solution was to just have the inverter trip and stay offline during any power system disturbance, thus avoiding the issue of providing a ground path for the high side of the service transformer. As the amount of solar on a feeder increases above 15%, everything gets more complicated.

Voltage regulation at the customer's premises can be an issue. If the utility feeder is at 105% voltage on the medium voltage side and an inverter is backfeeding through the service wire and service transformer, the customer's equipment could be damaged by voltage well above 105% on the 120/240V side.