I am in need of help...I am working on a piece of equipment that generally has low voltage running to it.

The fix is to install a transformer ahead of this piece of equipment to boost the voltage.

In order for the engineers to properly size this transformer, they have asked me to check the Rmains...I am confused about this. It is a 208v 30A line with a Nema 6-30 receptacle.

How do I measure the Rmains?

 

Hopefully, this helps.
http://www.patentstorm.us/patents/6208258/description.html
http://www.pes.ee.ethz.ch/uploads/tx_ethpublications/miniboeck_APEC01.pdf

Or, you can ask the engineers to clarify what they mean by r-mains.