The connections described below are correct for a four terminal connection box in a small power older type Brook's motor. If you are having difficulty starting or running an Inverter on this motor, this entry will help you.
The information was kindly provided by Nick Oldfield who spent some time in February 2009 with his motor and an ABB ACS150.
The motor was made for 400V/230V in 'star/delta' connection. The connections need to be changed to 'delta' for 230V 3ph, operation by removing the six wires from the four terminals and re-arranging the connections on three of the terminals. Incorrect connections will result in the drive being limited to about 20Hz while drawing excessive current and possibly tripping on 'Over-current'.
The drive behaves as if single phasing or being presented with a motor having an earth fault. What is happening inside the motor is not all of the windings are working as a team to provide a correctly rotating flux for the rotor. Some are opposing each other. To quote Nick's text...
For the record, the motor was a Brook Motor originally connected for 380V in STAR. The motor has four terminals (A, B, C & N): The original 400V STAR connection was: A = red (other end = black) B = yellow (other end = brown) C = blue (other end = white) N = black, brown & white For 240V DELTA, the correct connections are: A= red & brown B = blue & black C = yellow & white N = n/c This may help someone in the future? Best regards, Nick Oldfield