Measuring R1 in induction motor equivalent circuit and parameter extraction from test
The equivalent circuit is the line to neutral circuit for one phase of a wye connection. The wye equivalent circuit is used whether the actual motor connection is wye or delta. The component values are adjusted accordingly. R1 is determined from a DC resistance measurement. I believe that the measurement is usually done at the motor terminals with the motor connected as it is connected for the full-load and locked-rotor tests.

You should be able to find on the internet several versions of step-by-step instructions telling how to perform no-load and locked rotor tests. The instructions include the equations used to determine the equivalent circuit values.