How to know power consumption of core FPGA
If you are the one who designs hardware implementation - you will know it's power consumption when you use vendors development tools. Xilinx software automatically provides expected power consumption reports. I would expect Altera to provide similar reports as well.



If you do not work with hardware development directly, then it would be difficult to determine only the core power consumption, if it is not specified. You would need a board schematic to know which points to tap in that supply only the FPGAs core. This would likely involve breaking physically the circuits/traces to measure the current, given that they are exposed (not within the board layers).