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?

 

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?

Can you tell us the serial number of the transformer or something about it as we can find information about it?

 

Sounds like a 3-wire delta with grounded hot leg. I didn't think they were used any more. How old is this transformer?

 

Sounds like a 3-wire delta with grounded hot leg. I didn't think they were used any more

I agree, on both counts. Last place I saw that used that was 480 v w/grounded hot leg, something about that just doesn't seem right.

 

The transformer is a Square D Sorgel General Purpose
Cat # 150T6h
Style # 35149-28212-024
No serial #
The date code is 0608

The transformer was installed about a year ago.

 

Your connection is called a corner grounded delta. Not that uncommon in industrial settings. One leg of the delta is connected to earth. This connection may or may not be intentional. If there is a plant engineer available to you, he should be consulted.