The aerial cable coming into the meter socket has two insulated conductors and one bare (neutral) which makes me believe that it would be a single phase 120/240v system...the meter socket says 250v 3wire. I'm getting 250v phase to phase and both phases to what I believe to be the neutral....the motor that is hooked up and working seems to be a 3 phase motor with your high/low voltage winding leads....there is no nameplate on the motor to verify 3 or single phase.the customer has another 3 phase motor that he wants installed and I'm not 100% sure on what I'm working with here. never came across this type of system....just wondering if anyone knows what I'm dealing with. Thanks
Like was said it is called a corner grounded delta, the "B" phase is bonded to ground and in some older installations to what would be the neutral bar, so you have a grounded system and is also why you see 250 volts to ground, was very common in industrial and even in some older commercial, also many of these panels will also only have 2-pole breakers as there was no requirement to have one in the grounded phase, I have gotten many service calls mainly from HVAC techs who thought they had lost a phase because they only tested from line to ground at the HVAC unit, but it wasn't the case.
I have seen many installations that they just used a single phase panel with two pole breakers and the "B" phase landed on the neutral bar that was bonded to ground, I have also seen where someone not knowing this tried to land 120 volt loads in a panel like this and ended up with some burned up equipment, something to keep in mind.
as far as the voltage reading your getting while it could be a meter error, you could also have a utility transformer that was tapped at a higher voltage because of more loads in the past, but 250 volts is not that far off and within the 10% rating of 240 volts so it shouldn't be a problem.
So if the panel has 2-pole breakers in it, and "B" phase is landed on the neutral bar, and there is no existing breakers you can use, otherwise you will have to locate a straight rated 240 volt breaker to install a circuit for this saw, also if the panel is not already marked it should be marked 240 volts loads only no 120 volts to prevent anyone else from doing what I mentioned above.
