Newbie- 3 Phase Power Question

[KOzOK]

Hi guys I have a strange situation. We have Matsuura MC-600 with Fanuc 11M control. We have 3 phase 480V coming in stepped down to 220V. With machine off incoming power, when measured phase against ground, all phases look good ~130V, but with control powered up, two legs go up to ~230V and one leg drops down to 0.5V. When measured phase to phase is around ~230V. I have confirmed this with two fairly decent multimeters.

Now everything works fine, and I only just found this out because coolant pump went out. Is there anything I should be worried about?

Could someone smarter than me, try to explain what is going on. I have some understanding of AC wave, but I'm no electrical engeneer (obviously )

Thanks in advance,

KOzOK

[Al_The_Man]

If you have the schematics, confirm how the 3 phase secondary is connected, if in fact the secondary is connected in star mode, with the star point grounded or not.
Even with non grounded star point, it is possible to measure a high voltage from phase to ground because of the high impedance nature of the meter measuring leakage etc.
If this were the case and when the machine powered up, and a 3 phase device had a ground on it, you would get the measurement you read, but with no visible sign of a defect, because if the star point is not referenced to ground, a ground fault can occur and you would not know.
From the readings, It does not sound as though you have a grounded Delta system, however.
Al.