We're going to need a little more to go on. Could be a normal operating condition of a corner-grounded delta system. Or a non-normal condition of a more typical three-phase system.
It depends on the type of equipment. A standard motor and contactor will work, but you will most likely suffer from current unbalance. If you are going to be using drive or other more advance items, it depends on the manufacture. Some of the manufactures will allow it, other will reccomend against it. Is it possible to get a thrid transformer installed and close the delta? What part of the world is this?
Yes, it can work. Corner-grounded systems are not common anymore, but are sometimes still seen. As waross says, a common use is when an open delta configuration is used.
Do you have a three-phase transformer, three single phase transformers, or two single phase transformers serving this system?
My initial impression of the OP was that he was asking about a 240V delta system with a center grounded B phase to provide 120V, which were, and in some areas still are, common.
AKBUGG was my interpretation incorrect? Is this on a building service?
You may want to double check your information.
A "wild" B phase is more common than a grounded B phase although both exist.
With a wild leg system, phase A and phase C will measure 120 volts to ground, (One transformer center tap is grounded.), B phase will be 208 volts to ground.
Both systems may be either open or closed delta, but the wild leg system is often used on open delta.
There are issues with peak reverse voltages across the internal components of drives, that hopefully some of the drive gurus will address.
respectfully
That's a good point. I originally thought he was talking about a wild-leg system, but I guess I decided he was talking about corner grounding. On re-reading the OP, it could be either.
