Transformer voltage rating

[adamscb]

I'm looking at the voltage rating of a transformer, and it shows '240x480v' on the primary, and '120/240v' on secondary. I know that you can get either 120v or 240v on the secondary, but what does the 'x' mean on the primary?

 

[david luchini]

I'm looking at the voltage rating of a transformer, and it shows '240x480v' on the primary, and '120/240v' on secondary. I know that you can get either 120v or 240v on the secondary, but what does the 'x' mean on the primary?

The 'x' means you can connect the primary to either 480V or 240V.

 

[GoldDigger]

Whereas the 120/240 on the secondary means that you get both at the same time (I.e. center tapped)

 

[adamscb]

That makes sense. What's the point then of having a 240v primary, 120/240v secondary transformer? Isolation?

 

[augie47]

That makes sense. What's the point then of having a 240v primary, 120/240v secondary transformer? Isolation?

Although not very commonplace, there are still 240v 3 phase delta systems around (no neutral).
That is one scenario where the transformer you have would be useful.

 

[mike_kilroy]

That makes sense. What's the point then of having a 240v primary, 120/240v secondary transformer? Isolation?

yes. altho more common in the past, we used to use iso xmfrs to help reduce noise for example from servos get back to powerline. in addition to d-y conversion. also it allows an OEM to have one transformer part no. for their machine for customers with either input.