I work in an industrial food processing plant with a 480V 3 Phase supply power stepping down to 240V 3 Phase power using a transformer. When I go from 1 leg of the secondary power to ground I get 230V, the second leg to ground I get 230V, the third leg to ground is 0V. When I go from leg to leg I get 230V. My question is why do I get 230V leg to leg and why does the third leg have 0V?