Might work... but the inrush current of the VFD might be too much for the relay on the board... its could be marginal I reckon with a 2.2kW spindle. Also it is very bad practice to start the motor by switching on the VFD! You could probably, and more safely, use the relay to control the 'soft start' input on the VFD (might be labelled 'RUN' input). Then you will have to turn the VFD on and set the speed before pressing Start on the PC...